hydraulic creek hydrological risk assessmenta100.gov.bc.ca/appsdata/acat/documents/r17101/... ·...

Hydraulic Creek Hydrological

Risk Assessment

Prepared for:

BC Ministry of Environment

Prepared by:

Grainger and Associates Consulting Ltd.Salmon Arm, BC

and

Streamworks UnlimitedSalmon Arm, BC

August, 2009

Hydraulic Creek Hydrological Risk Assessment GACL File: 08-012BC Ministry of Environment August, 2009

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Table of ContentsEXECUTIVE SUMMARY ....................................................................................................... 41.0 INTRODUCTION .......................................................................................................... 72.0 METHODOLOGY ......................................................................................................... 7

2.1 RISK ANALYSIS ............................................................................................................. 82.2 MPB AND SALVAGE HARVESTING HAZARDS ............................................................... 10

2.2.1 MPB and salvage stand hydrological effects...................................................... 102.2.2 MPB and ECA.................................................................................................... 10

2.3 WATERSHED AND CHANNEL SENSITIVITY ................................................................... 132.4 ELEMENTS AT RISK...................................................................................................... 15

2.4.1 Water quality and water intake infrastructure .................................................... 152.4.2 Water Supply ...................................................................................................... 202.4.3 Fish ..................................................................................................................... 202.4.4 Social Infrastructure ........................................................................................... 21

3.0 WATERSHED CONDITIONS AND HAZARDS ..................................................... 223.1 WATERSHED CONDITION ............................................................................................. 22

3.1.1 Physiography, geology and terrain ..................................................................... 223.1.2 Channel conditions and bank stability................................................................ 253.1.3 Channel sensitivity ............................................................................................. 30

3.2 WATERSHED HYDROLOGY .......................................................................................... 313.2.1 Snow sensitive zone ........................................................................................... 313.2.2 Forest cover changes .......................................................................................... 323.2.3 Sub-basin ECA Scenarios................................................................................... 363.2.4 Flood frequency shift.......................................................................................... 383.2.5 Watershed Reservoir Management and Flood Regime ...................................... 40

3.3 HYDROLOGIC HAZARD ................................................................................................ 423.3.1 Peak flow hazard ................................................................................................ 423.3.2 Hydrologic hazard .............................................................................................. 433.3.3 Low flow hazard................................................................................................. 44

3.4 CLIMATE CHANGE ....................................................................................................... 463.5 WILDFIRE .................................................................................................................... 47

4.0 CONSEQUENCES....................................................................................................... 474.1 Water Quality and Infrastructure................................................................................ 474.2 WATER SUPPLY ........................................................................................................... 484.3 FISH ............................................................................................................................. 484.4 SOCIAL INFRASTRUCTURE ........................................................................................... 49

5.0 RISK ANALYSIS ......................................................................................................... 515.1 WATER QUALITY AND INFRASTRUCTURE .................................................................... 515.2 WATER SUPPLY ........................................................................................................... 525.3 FISH ............................................................................................................................. 525.4 SOCIAL INFRASTRUCTURE ........................................................................................... 53

6.0 CONCLUSIONS AND RECOMMENDATIONS ..................................................... 546.1 CONCLUSIONS ............................................................................................................. 546.2 RECOMMENDATIONS ................................................................................................... 55

7.0 CLOSURE..................................................................................................................... 57


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References

Figures in pocket

Figure 1 Hydraulic Creek Base MapFigure 5 Biogeoclimatic Unit MapFigure 17 Fish Consequence Value Map

Appendices

Appendix A Risk Analysis Definitions

Appendix B Summary of South Okanagan Stand Survey Results

Appendix C Channel Sensitivity Method and Results

Appendix D Hydraulic Creek Fish Values by Reach

Appendix E Flood Frequency Shift Analysis


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EXECUTIVE SUMMARY

Grainger and Associates Consulting Ltd. and Streamworks Unlimited carried out an analysis ofMountain Pine Beetle (MPB) and salvage harvesting-related risks to water quality, watersupply, fish habitat and other infrastructure in Hydraulic Creek Community Watershed.Hydraulic Creek, a 95km2 area draining into Mission Creek east of Keklown B.C., is theprimary water source for domestic, commercial and agricultural users in the South EastKelowna Irrigation District (SEKID).

The hydrological effect of MPB and salvage harvest forest cover disturbance was analysedusing recent research findings on snow accumulation and melt effects under different forestcanopy conditions, including the effects of the dead pine trees, non-pine overstory, andunderstory seedlings, saplings and poles in MPB-attacked stands (Huggard and Lewis, 2008).

Stand structure data for ECA modelling was collected in 245 random plots in 30 accessiblepine-leading stands in the hydrologically sensitive upper watershed “snow zone”, in sevenSouth Okanagan watersheds near and including Hydraulic Creek. Over 70% of these VRIlabelled pine-leading stands had healthy understory, averaging 560 to 1000 well-spacedstems/ha >1.3m tall, and non-pine overstory averaging 25 to 69% of total overstory basal area.These stands will have a significant hydrological function, even when all pine in the stand isdead.

Stand data was used in modelling two watershed level management scenarios. In the“MPB/unharvested” scenario, all pine trees in pine-leading stands are assumed to be killed byMPB, and no further forest harvesting activity takes place in the watershed. In the “fullclearcut salvage” scenario all pine-leading (>40% pine) stands are clearcut harvested, with theexception of riparian zones, old growth management areas, unstable terrain and other areasdesignated as long-term reserves by forest licensees.

In Hydraulic Creek Watershed the effects of forest canopy removal from pine mortality and/orharvesting result in moderate to high ECA hazards for the MPB/no salvage and the full pine-leading stand salvage scenarios respectively, with maximum ECA values of approximately50%. However hillslope runoff in Hydraulic Creek and adjacent watersheds is intensivelymanaged by SEKIDS, with inter-watershed transfers into and out of Hydraulic Creek duringreservoir recharge in the spring freshet. There are large storage volumes in numerousreservoirs and continuous discharge from reservoirs during the growing season to the SEKIDSwater intake in the lower Hydraulic mainstem. This management results in effectiveattenuation of watershed runoff extremes, with reduced freshet peak flows and increasedgrowing season low flows.

This reduction in runoff extremes, combined with low to moderate channel sensitivitiesthroughout the watershed, result in very low to low hydrologic hazards, following both theMPB/no harvest and the full pine-leading stand harvest management scenarios.

These small hydrologic hazard ratings result in very low to low risks of increased peak flowsand associated increased fine and coarse sediment at the SEKID intake, following the MPB/noharvest and the full salvage harvest scenarios respectively. That is, following the completemortality of all pine and with no further harvesting in Hydraulic Creek watershed, there is avery low risk of hydrologic impacts to the SEKIDS water intake. If all pine-leading stands in


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the watershed were harvested there would be a low risk of hydrologic impacts. Thereforenoticeable increases in flooding or sediment effects at the intake are not expected, followingeither scenario. However, turbidity levels have been and will continue to present a problem atthe SEKIDS water intake, in terms of meeting Interior Health Authority water qualityguidelines; such that alternative sources of domestic drinking water supplies are beingexplored. The very low to low hydrologic (flood and sediment) hazards suggest that asignificant part of the turbidity problems are likely due to organic particles and colour, whichusually originate in wetlands and reservoirs.

Significant advancement of freshet timing at the SEKID water intake is not expected followingthe MPB/unharvested scenario or the full salvage scenarios. While larger impacts to laterseason water shortages would be expected following the full salvage scenario, there is a lot ofuncertainty about how large an effect this could be; that is, how many days earlier maximumfreshet flows could occur. Because of extensive inter-basin flow routing and reservoirmanagement, for either management scenario this effect is expected to be relatively small, andwould not significantly affect reservoir storage in the later growing season. The effect onfreshet advancement and later growing season water supplies from global climate change isexpected to be larger than MPB/salvage impacts.

There are generally moderate fish presence and habitat values along the entire Hydraulic Creekmainstem and high values in the upper watershed lakes and in Reach 3 in the lower mainstem.Because MPB and salvage effects are not expected to significantly change conditions in thelakes or in the mainstem below McCulloch Reservoir risks to fish values are low almosteverywhere in the watershed. Risks to fish values in the lower Hydraulic mainstem areconsidered moderate, because of the slightly higher channel sensitivity to disturbance thanelsewhere in the watershed. However because of the very controlled flows below the reservoir,significant channel and fish habitat impacts are not expected.

Again, because of the low to very low hydrologic hazards throughout the watershed, risks tonon-municipal water supply infrastructure are also low to very low. The few private waterlicenses are located on upper watershed lakes, where little post-MPB or salvage impacts areexpected. The KVR / Trans-Canada Trail generally have adequate drainage structures with alow vulnerability to impacts. Forestry road drainage structures are located in the upperwatershed basins and appear adequate for current flows. They have a moderate vulnerability tothe generally low likelihood of significantly increased peak flows, for a low MPB/salvagerelated risk. Private farm bridges are considered highly vulnerable to increased peak flows.However their location below the McCulloch Reservoir, where discharge is highly controlledand increased peak flows are not expected following either management scenario, result in alow MPB/salvage-related risk to these structures.

The low risks associated with salvage harvesting assume normal good forestry practices toprevent significant hillslope runoff interception and concentration to streams, which couldincrease peak flow and sediment regimes in channels. In particular good riparian managementpractices are recommended. This includes maintaining adequate riparian reserves of stands thatoften have a significant non-pine component. These stands will provide long term temperaturebenefits, improved stream bank and floodplain stability and large woody debris recruitmentopportunities, if they are preserved and managed to prevent post- harvest blow-down.


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The data collection and modelling results in this investigation suggest that even if all pine-leading stands were harvested, there would generally be low hydrologic risks to all watershedvalues. However ECA analyses are based on average stand conditions derived from limitedfield measurements of secondary stand structure. It is apparent from our results that the localVRI data, particularly in under-estimating the non-pine component of stands identified as pine-leading, is somewhat to quite inaccurate.

From a strictly hydrological perspective (and we recognize forest managers have to balancemany different forest values), the least hydrological impact would result if pine-leading standswith the lowest non-pine overstory component and lowest understory stocking werepreferentially targeted for salvage harvest. The data collected for this investigation suggeststhat, on average, stands with the least hydrological function are younger MSdm stands followedby older MSdm stands and then ESSFdc stands. We recognize that individual stands withinthese broader classifications will have different characteristics, and it is understood that sitespecific evaluations of stand structure should supersede these broader recommendations inmaking harvesting management decisions. To that effect, licensees carrying out salvageharvesting in the watershed should measure and record secondary stand structure during recceand layout. They should then use that site specific stand data in a hydrological risk assessmentmethodology that models the effects of secondary stand structure, to determine the likelyhydrological effects of their actual harvesting and retention plans.

This would ensure watershed hydrologic effects are minimized, and avoid unintended localimpacts, should harvesting be concentrated in stands with high hydrologic functions nearpotentially sensitive stream reaches, such as those with high fish values or the steeper lowerwatershed tributaries.

With good hydrological risk assessment of specific harvest and retention plans, and with goodpractices during operations, salvage harvesting with a level of risk acceptable to stakeholdersshould be feasible. Nonetheless, the widespread and severe MPB epidemic in B.C. is clearevidence that forests can be subjected to significant unforeseen disturbances with potentiallysignificant consequences. Forest managers should be aware that MPB infestation may not bethe only significant stressor on Hydraulic Creek forests in the near future. Global warming andglobal warming-related disturbances such as other pathogens attacking other tree types (spruce,fir beetle and others) and significant wildfires, are not improbable in the near future. We thinkthat part of the determination of what is an acceptable level of risk should include consideringthe hydrological (and other) effects of these other possible disturbances. Thrn it would beprudent to apply the precautionary principle and preserve some forest hydrological function inthe watershed above the minimum required to manage only for MPB and salvage harvestingrelated impacts.


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1.0 INTRODUCTION

Grainger and Associates Consulting Ltd. and Streamworks Unlimited were retained by the B.C.Ministry of Environment to carry out an analysis of Mountain Pine Beetle (MPB) and salvageharvesting-related risks to water quality, water supply, fish habitat and other infrastructure inHydraulic Creek Community Watershed (Figure 1); as part of a contract to complete similarrisk analyses for seven south Okanagan Community Watersheds

Hydraulic Creek Community Watershed area is approximately 95km2 and drains into MissionCreek upstream of the city of Kelowna B.C. It is the primary water source for domestic,commercial and agricultural users in the South East Kelowna Irrigation District (SEKID).There is widespread fish presence throughout the Hydraulic Creek watershed. There arenumerous lakes in the watershed used by SEKID for water storage.

This report provides an analysis of risks to watershed values associated with potential changesin the forest following pine mortality due to MPB attack and salvage harvesting. Changes inforest cover affect watershed hydrology, and potentially water quality, quantity and timing.

The project was completed by the team of Bill Grainger, P.Geo., forest hydrology, risk analysisand project management; Alan Bates, P.Eng., hydrotechnical analysis, channel morphology,sensitivity and restoration; Jennifer Clarke, P. Geo.; background information and water quality,Michele Trumbley; R.P.Bio., fish population and habitat analysis, Dave Huggard, Ph.D., ECAmodeling; Stuart Parker, RPF, forest stand data collection and silviculture mitigation options;and Chris Long of Integrated ProAction Corp, GIS data analyses and mapping.

2.0 METHODOLOGY

This report utilizes extensive previously published materials on Hydraulic Creek watershedconditions, as well as a helicopter overflight and ground inspections on October 27, 2008.Forest overstory and understory were measured in 32 plots in four different areas in HydraulicCreek, as part of a program of 250 plots taken in 30 areas in seven south Okanagan Communitywatersheds. This detailed stand information was use in modelling the projected hydrologicaleffects of MPB pine mortality and salvage harvesting in Hydraulic Creek and the six otherwatersheds.

This report also incorporates recent research findings regarding the hydrological effects ofMPB-attacked stands over time, and research findings regarding potential stream flow regimechanges due to large scale watershed disturbances such as those resulting from MPB andclearcut salvage harvesting.

The watershed risk analysis procedure is presented in Section 2.1. Sections 2.2 and 2.3 explainhow forest cover changes, watershed conditions and channel conditions make up the hydrologichazard. Section 2.4 discusses the linkages between MPB and salvage harvesting-relatedwatershed processes and the various elements potentially at risk in the watershed. Current andpotential future watershed conditions in Hydraulic Creek are assessed in Section 3, todetermine potential hydrologic hazards. Section 4 details the presence and/or vulnerability ofspecific Hydraulic Creek watershed values (or consequences) that could be impacted by those


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hazards. Section 5 combines the hazards and consequences discussed in Sections 3 and 4 toarrive at qualitative risk ratings for each of the consequences potentially at risk.

Section 6 summarizes the various qualitative risks and proposes mitigative measures andmanagement strategies to reduce those risks, where necessary.

2.1 RISK ANALYSIS

Risk is a product of the incremental (increased) hydrologic hazard due to MPB and salvageharvesting, and each of the consequences which could be impacted by that hazard:

Risk = Hazard x Consequence

This is done using a risk matrix, as shown in Appendix A, Risk Assessment Definitions.

Figure 2 shows the risk assessment procedure used in this investigation. The incrementalhydrologic hazard starts with changes in the forest canopy, snow accumulation and snow melt.This is expressed as an Equivalent Clearcut Area hazard (ECA). Watershed characteristics –drainage density, slope and routing factors (reservoirs, lakes and swamps) determine how thewatershed will respond to changes in watershed ECA. A change in the flow regime is expressedas the flow hazard. How the flow hazard will affect stream channels depends on the existingchannel conditions, and how sensitive or robust the channel is to changes stream flows. This isdetermined from field observations and previously published channel assessments. Thechannel sensitivity and flow hazard are combined to form the overall Hydrologic Hazard.


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Water QualityWater Infrastructure

FishWater Supply Fan InfrastructureSummerland

CONSEQUENCES

PARTIALRISK

RISK RISK RISK

MPB stand snow accumulation / melt

Pre-MPB ECA - harvesting, fires

watershed stand characteristics - BEC sub-zones

Management – no salvage, total Pl leading salvage

ECA Hazard

INCREMENTALHAZARD

Watershed CharacteristicsSlope, drainage density, flow routing –basin response to hydrological inputs

Flow regime change – low flows,flood frequency shift

Flow Hazard

Stream Channel Sensitivitychannel, bank, riparian conditions

Potential for change in flow and sedimentregimes

HYDROLOGIC HAZARD

WATERSHED RISK ASSESSMENT

Figure 2. Risk Assessment Flow Chart


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2.2 MPB AND SALVAGE HARVESTING HAZARDS

2.2.1 Stand MPB and salvage hydrological effects

Mountain Pine Beetle and salvage harvesting primarily affect watershed hydrological processesthrough the loss of forest canopy and ground disturbance; when the pine beetle kills pine treesin a stand, and when clearcut harvesting removes trees. These can alter the water balance ataffected sites and, depending on actual weather and watershed characteristics, contribute to:less evapotranspiration and increased rain and snow reaching the ground, increased soilmoisture and hillslope flow, earlier onset of spring snowmelt, more rapid streamflow responseto storms, increased total stream flow and increased magnitude and frequency of peak flows(Winkler et al. 2008).

Ground disturbance and roads can lead to soil compaction, reduced infiltration to groundwater,shallow groundwater interception and redirection of intercepted water to streams. Theseprocesses can increase the “flashiness” of watershed response to rain and snowmelt inputs, andcontribute to elevated peak flows. Our experience with recent forest development in this area isthat with current forest harvesting and road drainage practices and mostly well-drained coarsetextured soils, these effects are relatively small compared to the effect of canopy removal, andthis is assumed to be the case in this analysis.

Clear-cutting harvesting results in complete canopy removal and leads to the maximumhydrological effects mentioned above. In the nival (snow-melt dominated) watersheds of thesouthern interior, such as Hydraulic Creek, these effects are caused primarily by theaccumulation of higher snow packs (expressed as snow water equivalent, SWE) in clear cutsthan in forests, and increased melt or ablation rates in clear cuts relative to forests.

There is a large volume of literature concerning the hydrological effects of clear-cutting, inwhich the extent of forest canopy removal or disturbance is often expressed as the EquivalentClear Cut Area (ECA); where a clear-cut has initially has an ECA of 100%, a mature forest hasan ECA of zero, and a regenerating forest has an ECA somewhere in between that isproportional to tree height and stocking (Anonymous, 1999). A watershed ECA value iscalculated by combining the ECA’s for various treatment and unharvested areas throughout thewatershed.

Our experience with analyzing hydrological impacts to watersheds using the ECA concept isthat because of the many simplifying assumptions necessary, there is always a large degree ofuncertainty regarding the final result, and it is not meaningful to apply watershed ECA resultsan accuracy of greater ±5%. In this report, when discussing the implications of ECA resultsthey are generally rounded to the nearest 5%.

2.2.2 MPB and ECA

In this study we model watershed ECA using the Huggard method (Huggard and Lewis, 2008),which incorporates recent research findings on snow accumulation and melt effects of differentforest canopy conditions in MPB attacked stands. This includes modelling the canopy effectsof the dead pine, the non-pine overstory and understory seedlings, saplings and poles.Research throughout BC to quantify the hydrologic function of dead pine trees and secondarystructure in pine-leading (>40% pine) MPB infested stands clearly demonstrates the important


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hydrologic function of unharvested MPB attacked stands, and supports the contention that theseeffects must be considered when evaluating the potential hydrologic risks associated with MPBrelated stand mortality relative to salvage logging (Redding et al., 2008a, Redding et al. 2008b,Winkler, et al. 2008 and FPB, 2007).

The stand structure data used in modelling Hydraulic Creek ECA was collected in 245 randomplots in 30 accessible stands in seven South Okanagan watersheds1 near Hydraulic Creek, withsimilar biogeoclimatic (BEC) stand types as Hydraulic Creek, and includes 32 plots taken inHydraulic Creek watershed. Appendix B “Summary of Results from South Okanagan StandSurveys for MPB-ECA Modeling” presents a summary of those field findings for secondarystructure in high elevation BEC zones in this area, and compares those findings with similarsecondary stand structure surveys taken elsewhere in the province. Where required this datawas supplemented with secondary structure stand data from the North Okanagan andThompson regions (Vyse et al. 2007), which showed similar results.

Huggard and Lewis (2008) found the ECA effects of the dead pine trees in a pure pine standcan initially contribute up to 60% ECA reduction in the grey-attack phase. ECA graduallyincreases over time as dead trees in the pine stand fall to the ground. The ECA of non-pineoverstory is considered directly proportional to the percentage of mature non-pine trees in thestand, which is presumed to remain constant over the time period analysed; and which variesgreatly between forest types (BEC variants). The understory components affecting ECAinclude existing poles, saplings and seedlings, and new seedlings, assuming a regenerationdelay of 20 years before full stocking. As the understory grows over time, stand ECA isgradually reduced. The change in ECA contribution over time from these three factors iscombined into a single curve representing the cumulative growth and/or decay of ECA of thedead pine stand over time. This was done for various BEC variants, percentages of pine in thestand, site productivity indices and other variables. Figure 3 is an ECA progression curve foran unharvested MPB attacked stand, showing the contribution of the three ECA reductionfactors (dead pine, non-pine overstory and understory) and the cumulative ECA curve over a 60year recovery period.

1. The seven watersheds are Lambly, Trepanier, Peachland, Hydraulic, Mission, Hydraulic and Penticton Creeks.


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0 10 20 30 40 50 60

02

04

060

80

10

0

Time since disturbance (yr)

EC

Ava

lue

(%)

Non-pine overstory

Dead pines

Understory

Figure 3. ECA projection (heavy green line) for unsalvaged older (>110yr) Montane SpruceBEC variant (MSdm) showing the contributions over time of non-pine canopy (black line,

showing a constant 35% ECA reduction over time) the dead pine (red line,showing decreasing ECA reduction as dead pines fall down over about 20 years)

and understory (light green line). Dashed lines are 95% confidence intervals.

Huggard and Lewis (2008) also conducted sensitivity analyses on many of the critical inputparameters, including percent mortality of natural understory, understory species composition,TIPSY vs. VDYP regrowth modeling, different regeneration stocking delays, and othermodeling components/assumptions. Generally the salvage vs. non-salvage ECA curves aremost sensitive to the percentage of non-pine overstory, as shown in Figure 3.

It should be noted that the solid lines in Figure 3 are average values of the many differentindividual site conditions one would encounter in actual stands of a particular BEC variant. Forinstance, in high pine component stands there will be sites with very little understory, and othersites with a well-stocked understory.

ECA curves for clearcut harvested attacked stands were also developed, based on expectedregrowth rates of planted stands. Figure 4 shows a comparison of the unharvested andharvested ECA progression over time, for the same stand type shown in Figure 3. Similarcurves were developed for all major BEC zones or subzones in the hydrologically importantupper portion of the watershed. The cumulative effect of the different ECA progressions indifferent BEC zones in the watershed is calculated, to arrive at a watershed ECA.


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0 10 20 30 40 50 60

02

04

06

08

01

00


EC

Ava

lue

(%)

Unsalvaged

C/C Salvaged

Figure 4. ECA projections for unsalvaged and clearcut salvaged and planted older MSdm, showing thatECA for unharvested MPB attacked stands never rises above about 40%. There is a 20 to 25 year

period where the clearcut salvaged and replanted stand has a significantly higher ECA than theunharvested stand, after which the planted stand recovers slightly ahead of the unharvested stand.

It should be stressed that ECA hazard value alone is not necessarily a good indicator ofpotential watershed hazards. Each watershed and stream channel will respond differently tochanges in forest canopy that an ECA value represents, depending on watershed and channelcharacteristics, as discussed below.

2.3 WATERSHED AND CHANNEL SENSITIVITY

Where ECA levels are high, increased runoff is routed over slopes and is collected by channelsystems, accumulating flows downward through the watershed. How or whether stand levelchanges translate into downstream watershed level impacts depends upon the physicalattributes of the watershed and channels.

Drainage basin factors that affect runoff sensitivity include steepness, soil drainage properties,drainage density, soil depth (or proximity to an impervious layer), and natural storage (e.g.lakes, wetlands). Some of these characteristics are clearly interrelated, for example, a steepbasin with poor soil drainage usually has a higher drainage density. As shown in Figure 2 theextent of forest cover disturbance (denoted by ECA) is combined with drainage basinproperties to give a Peak Flow Hazard. Qualitative basin drainage characteristics were assessedfor this project using orthophoto/contour maps, soils maps, field observations and previouslypublished reports.

Channel response to changes in flow regime depends on natural channel attributes, which are areflection of grade, flow regime and the materials (soil and vegetation) that the channel passesthrough. Channels respond to increased flows by increasing their capacity, typically by


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widening through bank erosion (Church, 1993). Storage features such as lakes and wetlands(either on the channel or floodplain) can attenuate peak flows and lessen the impact of anincreased flow regime. Channels passing through coarser, erosion resistant materials willrespond more slowly to flow regime change, taking decades or more to adjust.

Table C-1 in Appendix C is a framework for assigning channel sensitivity ratings based oncharacteristics from field, airphoto and map observations based on Green (2005). Channelsensitivities are described in response to increased peak flow/flood frequency, increasedsediment delivery and decreased riparian function, and can result from any one or acombination of these stressors.

In this assessment, sensitivity focuses on the first two stressors in Table C-1, increased flowand sediment generation. In Hydraulic Creek, few significant sediment sources, such aslandslides and road erosion, were identified outside of the stream bed and banks. While thisassessment does not include a comprehensive inventory of road and trail conditions, this hasbeen completed in the past. Sites were identified for rehabilitation and that rehabilitationcarried out in 1997 (Dobson, 1999). Given the largely gently sloping plateau terrain, and theadequate bridges, culverts, and deactivation observed in this investigation, it appears thatsediment loading to channels from existing forest road infrastructure has not been significant.Most sediment is generated from channel beds and banks during high flows, and by the ‘firstflush’ (rising limb of spring hydrograph) of materials deposited in the channel since theprevious high water. Therefore increased peak flows, sediment generation and turbidity areconsidered closely related.

Loss of riparian cover due to MPB is not considered a major issue as the component of pine inwetter riparian zones tends to be less than elsewhere across the landscape. Wei et al, (2007)found similar large woody debris (LWD) input rates in the Okanagan for MPB-attacked andnon-attacked stands. Hassan (2008) investigated sites in central BC and concluded that MPBinfestation-related wood transfer to the channel in the next 25 years is likely to be relativelysmall and within the range of typical conditions found in the region. Therefore, in HydraulicCreek, MPB-related short term increases and long term decreases in LWD recruitment are notexpected to be major or to have a significant effect on channel stability and fish habitat. Asubstantial portion of the Hydraulic Creek drainage system above McCulloch Reservoirconsists of diversion ditches constructed to deliver runoff from areas outside the naturalwatershed boundary. These artificial channels are likely to be less sensitive to changes inriparian conditions than a natural channel; however shading can still be important to moderatetemperature. It will be critical that salvage harvest plans maintain appropriate riparian reservesto preserve stream stability, fish habitat quality and temperature along watercourses.

Channel sensitivities were interpreted according to the framework presented in TableC-1, basedon field observations, airphoto and map reviews, and observations and conclusions frompreviously completed channel assessments. Earlier assessments were typically aimed atdocumenting levels of disturbance in channels and observed indicators of disturbance wereassumed to also be indicators of channel sensitivity or ‘robustness’. These results were carriedforward into this assessment. Channel sensitivities vary along the length of the stream. For thepurposes of this assessment, sensitivities were assigned by sub-basin, based on the relativeextent and location of sensitive reaches within that sub-basin.


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Once channel sensitivity has been determined, it is combined with the Peak Flow Hazard togive a Hydrologic Hazard for the drainage area (Figure 2). The Hydrologic Hazard thereforeincludes forest cover ECA effects, sub-basin drainage characteristics and channel sensitivityrolled up into a single hazard reflecting the potential for channel change, and is an expressionof expectations regarding peak flows and sediment delivery at the drainage outlet.

2.4 ELEMENTS AT RISK

Watershed elements potentially at risk from the hydrological effects of MPB infestation andsalvage harvesting are:

Water quality and water intake infrastructure, primarily at the South East KelownaIrrigation District (SEKID) water intake.

Water supply at the SEKID intake.

Fish populations and habitat

Social infrastructure (infrastructure not related to municipal water supply)

2.4.1 Water quality and water intake infrastructure

The water quality element at risk can be expressed as “a sufficient and reliable supply of safeand aesthetically acceptable water” (MoH, 2005), at the South East Kelowna Irrigation Districtwater intake on Hydraulic Creek. As well, potential damage or increased maintenance costs tothe SEKID water intake are considered.

Table 1 shows the various parameters identified by Ministry of Health (MoH) and Ministry ofEnvironment (MoE) stakeholders that, if compromised, could reduce drinking water aestheticappeal, increase the risk of microbiological activity and impacts to human health, and decreasethe effectiveness of primary disinfection treatment.

The potential link to MPB and/or salvage effects is evaluated for each parameter, which isjudged to be weakly linked, moderately linked, or strongly linked; and the rationale is providedas follows.

Table 1. Water quality and water supply infrastructure parameters

Element at Risk Effects of Concern Specific Parameter Metric Parameter or Watershed Sensitivity

FINE SEDIMENT(Turbidity)

NTU

FINE SEDIMENT(Total Suspended

Solids)concentration, mg/L

Hydraulic Creek exhibits elevated turbidity (related to fine sediment, organics andcolour) during the freshet. Some of the problem may be related to a ‘first flush’ of

channel areas that have been dry for extended periods (similar to urbanstormwater systems). Diverted flows consistently fail to meet IHA water qualityrequirements, and boil water advisories result. Sources of fine sediment and

organics affecting the intake are inferred to be downstream of McCullochReservoir. Hence, the lower watershed is sensitive to disturbances that will

increase fine sediment concentrations.

Reduced aestheticappeal and increasedrisk of microbiologicalactivity. Decreased

effectiveness of primarydisinfection treatment

Temperature oC

Loss of riparian forest shade can result in increased stream temperatures. MPBeffects are limited because there is less pine in riparian areas. Salvage willremove forest shade if riparian zone is harvested. With long term riparian

retention, salvage effects will be limited.

True Colour True Colour Units

Total OrganicCarbon

concentration, mg/LReduced aestheticappeal and human

health effectsMetals (select) concentration, mg/L

Total Phosphorous concentration, mg/L

Little published evidence to link changes in these water quality parameters to MPBinfestation or salvage harvesting

Nitrate & Nitrite concentration, mg/LDifficult to generalize effects on nitrogen cycle due to complexity. There have beenincreased concentrations of dissolved inorganic nitrogen (nitrates and ammonium)

following MPB mortality . Hydraulic Creek nitrogen levels are low.

Reduced aestheticappeal and increasedrisk of microbiological

activityAquatic Flora

(algae)mg per m2

Difficult to generalize due to complex interaction between canopy closure, streamtemperature, nutrient concentrations, and sedimentation. However, net effect is

expected to be an increase in primary production. Algae levels in Hydraulic Creekare unknown.

Drinking WaterQuality

Human health(waterbournepathogens)

MicrobiologicalIndicators

Fecal coliform,E. Coli bacteria

MPB infestation and salvage harvesting could have an indirect effect onmicrobiological indicators associated if there are changes in range use and

recreational activities associated with salvage harvesting access.

Water SupplyInfrastructure

Treatment infrastructuredamage

COARSESEDIMENT

cubic metres

In Hydraulic Creek, coarse sediment is mobilized from bed and bank erosion in thechannel. In lower reaches without lakes, mobilized sediment may be transferred

downstream to affect intake structures and other values. The watershed issensitive to disturbances that will increase coarse sediment production,

particularly in lower reaches downstream of any lakes.

Parameter not strongly linked to MPB effects, or lack of data to infer trends

Parameter with some link to MPB effects; can infer potential trends

Parameter linked to MPB effects; partial risk analysis completed


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Parameters weakly linked to MPB and salvage harvest effectsFor True Colour, total organic carbon, metals, and total phosphorus there is little publishedevidence to link changes in water quality to MPB infestation and mortality. In general, theseparameters are watershed specific and are more dependant upon the physical watershedcharacteristics (i.e. presence of wetlands, organic soils, geological and mineralogicalconditions) as opposed to watershed forest cover changes. Hydraulic Creek has high TrueColour Unit (TCU) values.

However, since these parameters are considered weakly linked to MPB and salvage-relatedprocesses, especially if riparian management is adequate, they are not considered further inthis study.

Parameters with some link to MPB and salvage harvest effects:The following parameters are considered to be moderately linked to MPB and/or salvageharvesting effects. Potential post-MPB and salvage trends may be inferred, although notwith a high degree of certainty. Characteristic source water quality of Hydraulic Creek isbased on limited sampling between 1986 and 1988 (MOE, 1990) and a summary of SEKIDwater quality data measured at the intake from 1993 to 2006 (Associated, 2007).

TemperatureThe provisional water quality objective for temperature at the SEKID intake site ismaximum 18oC (MOE, 1990), which suggests that stream temperatures are seasonallyelevated.

Although the loss of riparian forest shade can result in increased stream temperatures, asdiscussed in Section 2.3, loss of riparian cover due to MPB is not considered a major issueas the component of pine in wetter riparian zones tends to be less than elsewhere across thelandscape. Wei et al, (2007) found similar large woody debris (LWD) input rates for MPB-attacked and non-attacked stands in the Okanagan, which suggests that wholesale loss ofriparian forest canopy and streamside exposure to significantly increased incident solarradiation is unlikely in MPB attacked areas.

The potential temperature effects of salvage harvesting will depend on appropriate riparianmanagement strategies. Our understanding is licensees intend to maintain reserves zonesand management zones along all major streams. Small headwater streams in cut blocks maystill be vulnerable to temperature effects, depending on stand composition and riparianmanagement.

While it is expected any change in Hydraulic Creek stream water temperatures due to MPBand salvage will be small, any change would be an increase in temperatures alreadyseasonally above optimum levels.

Nitrate/NitriteLimited source water monitoring from 1997 to 1999 in Mission Creek found nitrate / nitriteconcentrations were below guidelines established for the protection of drinking water andaquatic life in surface waters (MOE, 2008).


18

Following both MPB and salvage harvesting increased concentrations of dissolved inorganicnitrogen (nitrates and ammonium) could occur. While elevated stream water nitrateconcentrations have been measured following MPB infestation, levels did not exceeddrinking water standards (Stednick, 2007). The complexity and interactions of the terrestrialand aquatic nitrogen cycle makes it difficult to predict MPB infestation or salvage harvesteffects with any degree of certainty; however it is expected any change in nitrite/nitrateconcentrations will be small, and will not result in any significant increase above drinkingwater source standards.

Microbiological IndicatorsElevated concentrations of fecal coliform and E. coli at the BMID intake on Mission Creekoccur most frequently between May and October; a time of year when livestock grazing onCrown range land seek out shade and water in riparian areas (MOE, 2008). Depending onthe extent to which Hydraulic Creek is utilized for livestock range use, concentrations ofmicrobiological indicators in Hydraulic Creek are expected to be seasonally elevated.

MPB infestation and salvage harvesting are not expected to have a significant direct effecton fecal coliform and E. Coli levels in Hydraulic Creek. However, changes in access due toa larger forest road network associated with salvage harvesting could have an indirect effect.For example, inadequate sanitary waste management by recreational users and the presenceof livestock in stream channels or riparian corridors could contribute to elevated levels ofcoliform bacteria. Since activities are typically dispersed throughout the watershed and soilsact as an effective filtration medium, water contamination may be mitigated through the useof suitable riparian buffers.

Given the fairly widespread road access that already exists in much of the watershed anyincrease in fecal coliform and E. Coli levels in Hydraulic Creek is expected to be small.However, it will be cumulative with existing levels.

Parameters Strongly Linked to MPB and salvage harvest effects:

The water quality parameters most strongly linked to MPB infestation and/or salvageharvesting are changes in fine and coarse sediment production. Increased sedimentproduction and transport to the SEKID water intake is a concern, because the changes inforest canopy affected by MPB and salvage can be similar to the effects of forest harvesting;namely, changes in riparian vegetation, increased magnitude and frequency of peak flows(floods), and sediment production from landslides, surface erosion and stream channel bankand bed sediment mobilization.

Fine Sediment

High turbidity levels are a concern in Hydraulic Creek during spring freshet high flowperiods. Increased fine sediment production and transport to the water intake is a concern,because suspended sediment concentrations, measured as turbidity and total suspendedsediment (or non-filterable residue) can act as a vector for pathogens that can affect humanhealth, decrease primary disinfection treatment effectiveness, and decrease the aestheticquality of water. In addition, significant increases in sediment concentrations may placeadditional stress on the treatment facility. Turbidity typically ranged from 2 NTU to 6 NTU


19

between 1993 and 2006, well above Guidelines for Canadian Drinking Water standards(Associated, 2007). SEKID receives frequent water quality complaints from water usersdue to turbidity and colour, particularly during spring runoff, and boil water advisories arecommon because treatment is less effective with high turbidity. It is not clear how much ofthe ongoing problems are caused by sediment and how much is related to colour and/orparticulates from organic sources. SEKID describes the problem as “Each year the Districthas turbidity problems associated with spring runoff. The problem is caused by high flowsin Hydraulic Creek (where our intake is located) caused by the melting of snow below ourreservoir. The melting snow causes the creek to rise and wash tiny particles of clay, silt,organic and inorganic matter, plankton, and other microscopic organisms into the District’sintake (SEKID Newsletter Vol 2, Issue 9, Spring and Summer 2009).

Turbidity and colour values are above IHA standards frequently enough that SEKID isexploring various management options. Options include increased surface water treatment,or alternate ground-water sources to supply domestic need (which comprise 15% of demand)and a separate delivery system for agricultural and fire protection (which comprise 85% ofdemand) which would not require treatment (Associated, 2007).

Coarse Sediment

Coarse sediment production, measured as bed load, can disrupt or damage water intakeinfrastructure. We are not aware of any bed load measurements in Hydraulic Creek near theSEKID intake. As discussed in Section 2.3, most sediment is generated from channel bedand bank erosion during high flows. That is, any sediment mobilized is already in thechannel and can be transported downstream, eventually to the community water intake andother values. Therefore, the watershed is considered sensitive to disturbances that willincrease coarse sediment production.

Water Quality Risk Analysis Procedure

A complete risk analysis would consider not only the stream flow and sediment hazards, buthow vulnerable the entire water delivery system could be to sediment impacts; by looking atall the water supply system protection barriers from intake to tap including intakeconfiguration, treatment processes, storage and distribution components, systemmaintenance, water quality monitoring, operator training and emergency response planning.

Interior Health Authority B.C. requested we do not evaluate the robustness or vulnerabilityof the South East Kelowna Irrigation District water intake or treatment facilities; rather thatwe look only at any incremental hazards due to MPB and salvage harvesting that couldaffect source water quality, supply and infrastructure integrity at the SEKID water intake(Dale Thomas, pers. comm.). The source water quality findings of this investigation can beused as input to a more comprehensive “Source to Tap Risk Assessment” that waterpurveyors are required to complete (MoH, 2005).

Studies that determine potential hazards and identify the elements at risk from those hazards,but do not evaluate their vulnerability, are known as partial risk analyses (Wise, et al. 2004).In this analysis the partial risk will be equal to the MPB-related hazardous conditions that


20

could compromise water quality at the SEKID intake, which are discussed in Section 3 ofthis report.

2.4.2 Water Supply

In the South Okanagan risks to water supplies come from changes in watershed conditionsthat could compromise the ability of storage to meet agricultural and domestic demandsduring the growing season, when there are large natural moisture deficits. MPB relatedeffects most likely to be noticed are changes in runoff timing. It is well known from studiesof the effects of clearcutting in nival (snowmelt dominated) watersheds of Interior B.C. thata reduction in forest canopy can lead to earlier freshet snowmelt. This can lead to waterusers having to access storage water at an earlier date and therefore for a longer period oftime, which can increase the risk of depleting storage before the end of the growing season.MPB attacked stands lose some canopy function, or are salvage clearcut harvested, in whichcase 100% of the canopy is removed. Therefore snowmelt timing effects similar toharvesting are expected in MPB and salvaged stands.

With the addition of the Turtle Lake Reservoir, flow diversions into Hydraulic Creek and thelarge lake storage capacity are expected to meet projected agricultural and domestic demandfor the next decade (Associated, 2007). Because of the large storage capacity relative towatershed runoff contributing area, Hydraulic Creek is considered less susceptible toreservoir depletion due to earlier snowmelt than most other Okanagan communitywatersheds.

2.4.3 Fish

Sportfish species within the watershed include Brook Trout (Salvelinus fontinalis) andRainbow trout (Oncorhynchus mykiss). Numerous lakes are stocked within the HydraulicCreek sub-basin, therefore fish presence was largely confirmed through stocking records.Obstructions to upstream fish migration include a series of dams at the outflows of BrowneLake, Long Meadow Lake, Haynes Lake and Hydraulic Lake. The dams are an obstructionto the movement of fish upstream however fish have been documented upstream of thebarriers. In addition, all lakes are known to contain fish with the exception of Long MeadowLake and Weddle Lake, therefore fish presence is likely throughout the watershed despitebarriers to upstream fish migration.


21

Table 2. Stream reach fish consequence value criteriaCriteria

ConsequenceRating

Fish SpeciesPresent

ChannelWidth (m)

ChannelGradient

%Habitat Quality

Very Low fish absence <1.5 >20%

fish absenceconfirmed, minimal

fish habitat available,habitat degradation

low risk to fish

Lowpresence of

RB0-5 16% - 19%

fish absenceconfirmed and/orhabitat with low

rearing potential forthe fish species

present

Moderatepresence of

RB, EB0-5 8% to 15%

habitat quality low tomoderate

Highpresence ofRB, EB, MW

0-20 0% to 8%

fish presenceconfirmed, habitat

quality moderate tohigh

Very High

presence ofRB,

EB, BT, KO,MW

0-20 0% to 8%fish presence

confirmed, habitatquality high

Impacts to fish and fish habitat following changes in forest cover due to MPB and salvageare likely to be similar to forest harvesting effects. These include loss of riparian vegetationwhich can affect fish shelter, stream temperature, nutrient availability and large woodydebris recruitment to streams. Increased peak flows and sediment can alter channelmorphology, resulting in degraded spawning, rearing and over wintering habitat. For eachHydraulic Creek and tributary reach, hydrologic hazards are determined (see Section 3) andcombined with the consequence values for each reach (see Appendix C), and for cumulativedownstream reaches, using a standard risk matrix (Appendix A).

2.4.4 Social Infrastructure

Social infrastructure refers to structures other than the SEKID water supply infrastructure,which in Hydraulic Creek is limited to a Kettle Valley Railway crossing, several farm andfootbridge crossings in Reach 5 (agricultural zone) and forest road crossings on tributaries.Private (non-SEKID related) water licenses exist on Browne Lake, Knox Creek and PearLake.


22

3.0 WATERSHED CONDITIONS AND HAZARDS

3.1 WATERSHED CONDITION

3.1.1 Physiography, geology and terrain

Hydraulic Creek is a tributary of Mission Creek, joining it approximately 10 km fromOkanagan Lake. Draining approximately 95 km2, Hydraulic Creek represents 15% of theMission Creek drainage area. Elevations in the watershed range from 540m at MissionCreek to 2100m at the summit of Little White Mountain adjacent to Canyon Lakes (includedthrough diversion).

Most of Hydraulic Creek Watershed is dominated by a rolling, gently sloping glaciatedupland plateau between elevations of 1300 and 1600m, typical of the Okanagan HighlandsPhysiographic Region (Photo 1). Only in the lower reaches above the SEKID intake isHydraulic Creek incised into the plateau, with predominantley moderate (30 to 50%)gradient slopes valley sideslopes, with some moderately steep (50 to 70%) slopes (Photo 3).

Bedrock is mapped as primarily undivided Proterozoic and Paleozoic metamorphics rocks ofthe Shuswap Metamorphic Complex with some younger Miocene and Pliocene basaltvolcanic rocks downstream and north of McCulloch Reservoir.

Soils in the watershed are typically moderately coarse to coarse textured morainal materialwith some colluvium on steeper slopes and organic and glaciofluvial sediments on gentlerslopes. Drainage density of streams on the plateau is low. Numerous lakes and wetlandsexist in this area, many of which have been dammed for use as water reservoirs.

Flows from neighbouring watersheds are diverted into Hydraulic Creek storage (e.g. KLOCreek). Excess flows may also be spilled into other watersheds (e.g. into the Kettle Riverdrainage). The plateau area accumulates considerable snow pack during the winter months.Normal precipitation is 700 mm annually measured at the McCulloch Station (elev. 1250m). Peak flows at the mouth of Hydraulic Creek are typically in the 1 to 4 m3/s range(Dobson 1998).

In 1982 and 1983, to improve water quality sections of Hydraulic Creek downstream fromHydraulic Lake were channelized where the creek flowed through a swampy meadow(Photo 2). Some of the meadow areas have been developed for agricultural use. LowerHydraulic Creek flows through a narrow canyon before joining Mission Creek. Myra Creekjoins Hydraulic Creek approximately 600m above the SEKID intake. A section of lowerHydraulic Creek above the intake was also channelized to make room for an access road.

Road deactivation has been carried out in the watershed for high priority sites identifiedprior to 1998 (82 kilometers of road addressed). This included replacing collapsed or failedwooden culverts and generally restoring natural drainage patterns. Two landslides wereidentified in the Hydraulic Creek watershed during the reconnaissance level channelassessment; both are located within the steep canyon of lower Hydraulic Creek. One ofthese landslides was related to diverted water from an abandoned irrigation flume and theother was considered natural (Dobson 1998).


23

Photo 1. Outlet of McCulloch Reservoir on broadgently sloping upland plateau area of Hydraulic Creek.

Photo 2. Low gradient Reach 5, below McCulloch Reservoir, Hydraulic Residual Sub-basin.


24

Photo 3. Reach 2 in Hydraulic Residual Sub-basin above SEKID water intake.

The SEKID intake is located at an elevation of approximately 650m, 2.3 km upstream of theMission creek confluence. There are two small settling ponds at the intake site.

SEKID provides water both for agricultural irrigation (85% of demand) and domesticconsumption (15% of demand). Compared with other irrigation districts supplyingKelowna, (e.g. Black Mountain Irrigation District), SEKID provides a higher percentage ofagricultural water. Domestic consumers are focussed around Gallagher’s Canyon and in theHall Road area. The Hall Road area is supplied with non-chlorinated groundwater. All othercustomers are supplied high elevation watershed water from Hydraulic Creek disinfectedusing chlorine.

The canyon downstream of the SEKID intake and its drainage areas is not included inanalyses of hydrologic impacts to the intake. However because of the relatively steepchannel gradient and confined channel through the canyon downstream of the intake, anyincreases in stream flows and sediment at the intake will be transported through the canyonto Mission Creek. Mission Creek has a large alluvial fan between Hydraulic Creek andOkanagan Lake through the City of Kelowna. The channel on the Mission Creek fan hasbeen straightened and dyked to protect adjacent developments from flooding.


25

Table 3. Hydraulic Creek Watershed and sub-basin areas

Sub-basinName

Sub-basinArea (ha)

TotalTributaryArea (ha)

Sub-basinArea aboveH-line (ha)

ElevationRange

(m) Reservoirs

McCulloch 4343 4343 23061275-1800

Reservoir (Hydraulic Lake,Minnow Lake, Haynes Lake andTurtle Lake (new).)

Fish Lake 419 419 561275-1400

Browne Lake, Fish Lake, LongMeadow Lake

HydraulicResidual 4618 9379 556 640-1275

None

3.1.2 Channel conditions and bank stability

Existing conditions in the Hydraulic Creek watershed derived from field and office reviewsare summarized in Table 4. Channel conditions are summarized by sub-basin although someissues may only apply to specific reaches within that sub-basin. Average channel gradientsare just that, and actual channel gradients will vary from the overall average. Listed channelmorphology types represent the predominant morphology of the mainstem channel withinthat sub-basin (Hogan 1997). Morphologies of some sections or tributaries in the sub-basinwill certainly vary. Although erosion, transport and deposition clearly occur everywhere ina channel system, the sediment regime descriptor provided in Table 4 gives an indication ofthe dominant sediment process for the mainstem channel in the sub-basin, whether it isoverall a source area, a transport or a depositional zone.

Upper stream reaches situated above McCulloch Reservoir within the McCulloch Creek sub-basin are characterized as stable riffle-pool and cascade-pool cobble/boulder channels.Limited channel disturbance was noted above the McCulloch Reservoir mainly due to thelow stream gradients. Throughout the watersheds, no evidence of extensive bank or channelinstability was noted and impacts from possible increases in peak flows associated with pastdevelopment were not discernible (Dobson 1998). Any sediment originating upstream ofthe McCulloch Reservoir is likely to settle in the reservoir and not be transported into thelower mainstem and/or the SEKID intake.


26

Photo 4. Cobble-boulder channel of Reach 8, Hydraulic Creekmainstem between Duck Lake and McCulloch Reservoir.

Photo 5. Reach 3, high fish values in Hydraulic mainstem belowMcCulloch Reservoir. Left bank harvested and blowdown to stream edge.


27

Dobson (1998) characterized mainstem channels in the Hydraulic Creek watershed belowMcCulloch/Hydraulic Lake as having stable to slightly disturbed, boulder/cobble cascade-pool or gravel riffle-pool morphologies (Photo 5).

In the early 1982/3, sections of Hydraulic Creek downstream from Hydraulic Lake werechannelized where the creek flowed through a swampy area known as Wardlaw Meadows(Reach 5, Photo 2). The intent of the channelization was to improve water quality byreducing the level of organics and/or colour acquired by the creek as it flowed through thewetlands. The channel appears to have remained stable with little evidence of bank erosionthrough this low gradient section.

Reaches 1-4 above the SEKIDS intake have moderately steep (50 to 70%) to steep (>70%)rocky, dry valley walls, with mostly intact riparian areas occupied by mature forest. A smallarea of the sub-basin was burned in the 2003 Okanagan Mountain Fire. An access roadabove intake pond has required some channelization of the mainstem.

Two landslides on the valley sidewalls are visible on air photos; one natural, the otherrelated to old irrigation ditch Dobson (1998). One of these landslides is directly connectedto the mainstem channel on north bank midway between McCulloch Reservoir and theSEKID intake, and appears to contribute sediment directly to the channel. Most of thechannel appears stable with some alluvial sections and bedrock controlled sections at lowerend. No ground survey of this section of the mainstem has been completed in this orprevious investigations that we are aware of.

Hydraulic Creek Hydrological Risk Assessment GACL File: 08-012BC Ministry of Environment April, 2009

28

Table 4. Channel Characteristics and Conditions

Sub-basinName Reaches

MainstemChannelLength

(km)

AverageGradient

(m/m)

DominantMorphology

Type*SedimentRegime Sub-basin/Channel Characteristics

McCulloch 6 to 9 12.1 0.03 RPg/ditchlinesSource/

Deposition

Natural lakes and wetlands augmented with dams toincrease available storage. Diversion ditches from CanyonCreek and Pooley Creek (upper KLO) to augment sourcearea. Excess inflows spilled into other watersheds.Numerous controls and artificial connections. Natural flowregimes significantly altered. Low drainage density andgenerally low gradients between reservoirs on plateau.Natural channels small (less than 3m wide) and generallylow gradient.

Fish Lake 1 1.9 0.02

RPg/ditchlinesand extended

culverts Source

Natural and controlled lakes and wetlands on upper plateau.Piped sections down to Hydraulic Creek below McCullochReservoir. Low drainage density and generally lowgradients between reservoirs. Natural channels small andgenerally low gradient.

HydraulicResidual 5 2.0 0.005

RPg/s(cleared to

improve waterquality) Transport

Residual channel through Wardlaw Meadows belowMcCulloch Reservoir. Low density of tributary channels.Channelized through wetland area in 1982/3. Riparian ispredominately deciduous shrubs and/or cultivated. Welldefined meanders with no evidence of recent erosion. Farmbridge and footbridge. Reach ends at KVR crossing.

HydraulicResidual 1 to 4 12.5 0.06

CPc/g (somechannelized

sections) Transport

Residual channel below KVR crossing. Low density oftributary channels. Steep, rocky, dry valley walls. Mostlyintact riparian with mature forest. Access road above intakepond required some channelization of the mainstem. Smallarea of sub-basin affected by 2003 Okanagan MountainFire. Two landslides visible on air photos; one natural, theother related to old irrigation ditch Dobson (1998). Landslideconnected to channel on north bank midway betweenMcCulloch Reservoir and the SEKID intake. Mostly stablechannel with bedrock controls at lower end. Tributarychannels also appear stable, but no ground survey has beencarried out for the tributaries or mainstem above the intake.

*CP = cascade-pool; RP = riffle-pool; c=cobble, g=gravel, s=sand

Hydraulic Creek Hydrological Risk Assessment GACL File: 08-012BC Ministry of Environment April, 2009

29

Table 5: Channel Sensitivity

Sub-basinName

ToIncreased

PeakFlow

Comments/Rationale

ToIncreasedSedimentDelivery

Comments/Rationale

ToDecreasedRiparianFunction

Comments/Rationale

Combined PeakFlow/Sediment

Sensitivity

Potential OutputsAssociated withChannel Change

McCulloch L

Mostly low streampower channels andditchlines connectingreservoirs.Sensitivity of ditchlinesdepends on designand inlet controls. M

Sediment maycause aggradation inchannels/ditchesand accumulate inreservoirs. M

LWD may play a rolein lower gradientsections, includingimproved bankstability. Riparianvegetation provideslittle benefit toartificialchannels/ditchlines L

Increased flows andsediment loadingcould causeaggradation,widening anddestabilization ofdiversion channels.

Fish Lake M

Increased flows mayexceed capacity ofpiped section. M

Sediment maycause aggradation inchannels/ditches. L

LWD plays a limitedrole in diversionchannel stability. L

Increased flows andsediment loadingcould causeaggradation,widening anddestabilization ofdiversion channels.Culvert capacity maybe exceeded.

HydraulicResidualReach 5 L

Banks alongmeandering channelmay be somewhatsensitive to increasedpeak flows. Wetlandarea provides floodrelief. L

Little sedimententers from lake.Sediment sourcedwithin reach willlikely pass through.Some aggradationmay occur in lowgradient sections. L

Riparian has beenreduced throughcultivation with littleimpact. MinimalLWD in channel dueto clearing. Existingriparian limited todeciduous shrubs. L

Increased flows andsediment loadingcould causeaggradation andwidening in lowgradient/channelizedsections.

HydraulicResidualReaches1 to 4 M

Steep connectedvalley walls.Condition of banks arevariable with bedrocksection, some alluvialsections and at leastone landslide directlyimpacting channel.Channelized sectionadjacent to accessroad may be sensitiveto increased peakflows. M

Sediment mostlypasses through.Some aggradationmay occur in lowgradient sections. M

Mostly intact matureriparian forest. LWDlikely plays some rolein channel stability. M

Increased flows andsediment loadingcould cause erosionaggradation andsediment transport.


30

3.1.3 Channel sensitivity

Using the assessment framework outlined in Table C1, channel sensitivities for the HydraulicCreek watershed are summarized in Table 5. Sensitivity to changes in peak flows, sedimentregime and riparian condition are considered separately. Since changes in flow and sedimentregime are considered the most likely impacts to occur in association with MPB (riparianchange is not expected to be significant), a combined sensitivity rating to peak flow andsediment is assigned to each sub-basin. For the purposes of this assessment, assigned ratingsgenerally represent the sensitivity of the mainstem channel in that sub-basin. Potential outputsassociated with channel change are described in the table to provide an indication of issues thatmay arise if changes to flow/sediment regimes were to occur.

Sensitivities of natural channels to increased peak flows in Hydraulic Creek were found to below to moderate in previous assessments. This stems mainly from coarse substrates andassumed stable banks. Artificial connections and ditchlines may be sensitive to increased flowsdepending upon the design capacity of the ditch and the method used to control/divert flowsinto the ditch. In many areas of upper Hydraulic Creek diversion overflows drain into adjacentwatersheds, limiting peak flow impacts in Hydraulic Creek.

The piped section connecting flows from the Fish lake sub-basin will certainly have a finitecapacity. A ‘piped’ channel is very stable unless the capacity is exceeded. It is not knownwhere flows in excess of the pipe’s capacity are directed.

Sediment transfer in Hydraulic Creek is minimized in the upper watershed by low gradients andfrequent lakes providing opportunities for settling. In some areas, low gradient sections mayaccumulate sediment which could lead to aggradation.

Mainstem reaches in the Hydraulic Residual below McCulloch Reservoir were described asstable in previous reports; however inspections have been limited to helicopter over flights(Dobson, 1998 and this investigation). The source of fine sediments affecting turbidity valuesat the SEKID intake has not been identified. It is possible that some sediment originates fromdispersed sources that accumulate during the low flow season and are mobilized by springfreshet (first flush scenario). A landslide adjacent to the channel midway between the intakeand the McCulloch Reservoir is visible on recent air photos, and is likely contributing sedimentto the channel. A small, active bank failure was noted just downstream of the KVR crossing,and there may be others along the mainstem that are not visible from the air. As discussed inSection 2.4.1 it may that be non-sediment organics from reservoirs and wetlands may becontributing to ongoing turbidity problems at the intake.

Steeper tributary reaches, with harvesting and fire-related disturbance in their upper areas mayalso be a source of fine sediment at the SEKID intake. An overflight did not reveal anyobvious sediment sources along these channels.

With the exception of Reach 5 (agricultural section) riparian areas appear to remain mostlyintact in the Hydraulic watershed. Riparian vegetation is likely not critical for channel stabilityalong artificially developed water diversion ditches in the watershed. While there are somelocalized issues, there does not appear to have been significant channel impacts due to past highflow events.


31

3.2 WATERSHED HYDROLOGY

Hydraulic Creek watershed is a nival (snowmelt dominated) watershed although summerconvective storms may cause occasional runoff events. The average annual total precipitationfor the Hydraulic Creek watershed is approximately 730mm with approximately 50% of thetotal precipitation occurring as snowfall (McCulloch Climate Station 1971-2000). Averagemonthly precipitation ranges from 40 to 90mm. Normal annual runoff is 200mm for theMcCulloch Reservoir area (British Columbia Streamflow Inventory, 1961-1990). Thereforeapproximately 530mm , or 70% of average annual precipitation is lost to evapo-transpirationand possibly groundwater and diverted surface water flows out of the watershed.

The McCulloch and Fish Lake Reservoirs have greatly altered and attenuated stream flows inHydraulic Creek. There is no spillway on the McCulloch Reservoir into Hydraulic Creek.Overflows are instead directed into Idabel Lake and the Wilkinson Creek/Kettle Riverwatershed. Since construction of the reservoir system, peak flows within lower HydraulicCreek are solely the combination of reservoir releases and runoff from the residual areadownstream of the reservoir outlets. Reservoir releases are often close to zero at the time ofpeak snowmelt, leaving the residual area as the only source of flow during the freshet. Thisrepresents nearly a 50% reduction in effective basin size contributing to freshet peak flows.

3.2.1 Snow sensitive zone

It is widely accepted that for nival (snowmelt dominated) watersheds such as Hydraulic Creek,it is largely the upper portion of the watershed that produces peak flows during the springfreshet melt, because snow in the lower watershed has typically melted prior to peak flowsoccurring in the lower mainstem (Gluns 2001; Schnorbus and Alila 2004). The H60 (thecontour line above which 60% of watershed area is contained) is commonly used to define thewatershed area that is contributing snow melt runoff at the time of peak discharge. It should benoted that the H60 concept was developed for graded mountain watersheds, and not watershedswith large upland plateaux, such as Hydraulic Creek.

Measurements have been made of the elevation of the receding snowline at the time of peakflows in several south Okanagan watershed (Dobson, 2004a, 2004c and 2004d), includingMission Creek(Dobson, 2004b), of which Hydraulic is a low elevation tributary. In almost allcases the contributing snow zone was less than 60%. Based on six years of observations (1999to 2004), the position of the snow line in Mission Creek during the freshet period is between1400 and 1600m elevation.

It is reasonable to expect that, depending on snow pack and melt conditions, some variation inthe contributing area will occur; and that a rapid melt when the snow line (elevation) is stillrelatively low would cause the highest peak flows. The very largest peak flows are likelycaused by widespread radiation and/or other energy inputs (e.g., sensible and latent heattransfers and energy advected by rain) occurring simultaneously over a large area of thewatershed. This is probably especially true in watersheds where mid and upper elevationsconsist of relatively low gradient plateaux, as in Mission and Hydraulic Creeks. Therefore inMission Creek the 1400m elevation is considered the lower limit of the snowmelt contributingzone to mainstem peak flows. The 1400m contour is the H30 line for Mission Creek – that is30% of Mission Creek watershed area is above this line. For Hydraulic Creek the H30 contour


32

0 10 20 30 40 50 60

020

40

60

80

10

0


EC

Ava

lue

(%)

Unsalvaged

C/C Salvaged

0 10 20 30 40 50 60

02

04

06

08

01

00


EC

Ava

lue

(%)

Unsalvaged

C/C Salvaged

is at 1350m elevation, which is considered the lower limit of the peak flow snow meltcontributing zone for the watershed as a whole and for the upper elevation McCulloch Sub-basin. The lower elevation Fish Creek and Hydraulic Residual Sub-basins are almost entirelybelow the watershed H30 line, and even though there is no discharge from McCulloch Reservoirduring the spring freshet, there is an early spring freshet peak flow (see Figure 15, p.37), whichis totally derived from snowmelt in these lower basins. Therefore in these basins the entirebasin area is considered the snow melt contributing zone.

3.2.2 Forest cover changes

Stand Level ECA

Figure 5 shows the BEC stand types in Hydraulic Creek watershed. BEC polygons locatedabove the H30 line are coloured. MSdm, ESSF and IDFdk stands comprise 68%, 29% and 3%respectively of the area of Hydraulic Creek watershed in the snow zone above the H30 line. Asdiscussed in Section 2, different ECA progression curves were developed for the different BECunits. Figures 6, 7 and 8 show unharvested and harvested ECA curves for three BEC units.

As discussed in Section 2.2.2, the unsalvaged curves are based on field measurements ofsecondary stand structure taken in Vegetation Resource Inventory (VRI) labelled pine-leadingstands in seven south Okanagan watersheds for this project (see Appendix B). The curvesshown here assume full pine mortality, full understory survival and a site index (SI) of 15.

The ESSF plot (Figure 6) is based on 56 plots in 7 ESSFdc stands. In stands labelled as 100%pine or <80% pine, the actual measured overstory pine component averages 30.7%. The rest ofthe overstory was approximately equal amounts of spruce and balsam. The average understoryhas 1000 well-spaced stems (>1.3m tall) per ha.

Figure 6. ECA progression in ESSF Figure 7. ECA progression in youngerpine-leading stands. pine-leading MSdm stands (70 to 110 yr).


33

0 10 20 30 40 50 60

02

04

06

08

010

0


EC

Ava

lue

(%)

Unsalvaged

C/C Salvaged

Figure 8. ECA progression in olderpine-leading MSdm (> 110yrs) stands.

The younger MSdm plot (Figure 7) is based on 64 plots in 8 pine-leading stands. The measuredoverstory pine component averages about 90%. The average understory is average understorystocking of 280 well-spaced stems per ha (>1.3m tall) per ha. The older MSdm plot (Figure 8)is based on 85 plots in 10 stands with an average overstory pine component of 74.0 % and anaverage understory of 560 well-spaced understory stems >1.3m tall per ha.

These curves, and ECA recovery curves for IDF stands using data from Vyse (2007), were usedto generate cumulative harvested and unharvested ECA curves for the watershed area and allsub-basin areas. ECA calculations also included the existing harvesting and fire disturbances inthe watershed as of December, 2008, based on VRI data and information provided by forestlicensees operating in the watershed – Weyerhaeuser Canada and BCTS Okanagan-ShuswapBusiness Area.

Hydraulic Creek Watershed ECA

In watershed ECA modelling MPB attack was phased in over 5 years, and salvage harvestingfollowed 1 year behind the MPB. Two management scenarios were modelled as shown inFigure 9.

In the “MPB unharvested” scenario (green line) all pine trees in pine-leading stands areassumed to killed by MPB, and no further forest harvesting activity takes place in thewatershed. That is, all stands are retained and there is no salvage harvesting of pine-leadingstands and no harvesting of non-pine green wood. In the clear cut salvage scenario (purpleline) all pine-leading stands are clearcut harvested, with the exception of riparian zones, oldgrowth management areas, unstable terrain and other areas designated as long-term reserves, ascontained in GIS layers supplied by forest licensees. These areas are preserved, however ifthey are pine-leading it is presumed that pine dies from MPB attack.


34

In Figure 9 the MPB/unharvested scenario assumes full mortality of pine in pine-leading stands(>40% pine), and full survival of the measured understory.

These two possible end points on the possible development continuum were chosen so that themaximum difference in hydrological effects between harvest and non-harvest options could beshown. It is not expected that forest licensees would be able to salvage harvest all non long-term reserve attacked pine; however there may be other interests in the wood, such as bio-fuelusers or others we do not currently know about, who could conceivably be able to utilize moreof the pine. And the authors have analysed watersheds in other areas where MPB infestation ismore advanced, and where ECA values are as high as 75%, because almost all pine-leadingstands in a watershed have been salvaged harvested. Showing the maximum possiblehydrological effects of different management options gives forest managers information on thewidest possible range of potential hydrological risks in the watershed.

Hazard ratings for different ECA levels are also shown in Figure 9. The low ECA rating isbased on findings that noticeable peak flow increases or peak flow effects are not generallyexperienced in watersheds with ECA values of 20% or less. Because of this watershed ECA isconsidered recovered, or a low ECA hazard, when the ECA level is 20% or less.

0

10

20

30

40

50

60

0 10 20 30 40 50 60

Year

EC

A(%

)

CC Salvage MPB/Unharvested

Figure 9. ECA and ECA hazard projections for Hydraulic Creek Watershed above H30 elevation,assuming full pine mortality from MPB infestation and full understory survival for MPB and no

harvest scenario (green) and full salvage harvest of all pine-leading stands scenario (purple).

Low

Moderate

High

Very High


35

A moderate ECA hazard indicates that ECA (forest canopy) effects may or may not benoticeable, and if effects are noticeable, they are not expected to be large. A high ECA hazardrating indicates that significant ECA effects are likely; and a very high rating expresses agreater certainty about the expected occurrence of very significant effects.

In Hydraulic Creek Watershed, with the overstory and understory survival assumptions made,following MPB mortality and no further harvesting, no increase in peak flow magnitude orfrequency is expected. The current ECA in Hydraulic Creek Watershed is approximately 35%.VRI data show that almost 50% of the watershed is less than 40 years old, with much of thedisturbance occurring in the 1980s, when there was widespread harvesting in response to andearlier MPB infestation (Photo 7). There is so much area of these younger stands re-growingand contributing to watershed ECA recovery, that they dominate the ECA recovery curve, eventhough in the remaining older stands there are substantial beetle-susceptible areas2. In theMPB/unharvested scenario the increasing ECA in these recently attacked pine stands is offsetby the decreasing ECA in regenerating older clearcuts. Although there is no increase in ECAover current levels, and the watershed is recovering as ECA decreases, it would recover fasterif there were no MPB infestation causing pine tree mortality.

Photo 7. Large areas in Hydraulic watershed of regenerating pine stands harvested in 1980s.

If the remaining pine-leading stands are all clear-cut salvaged here will be noticeable ECAeffects. The centre of the area under the ECA curve following the hypothetical full salvagescenario indicates there will be a sustained high ECA hazard for about 15 years. Within thistime period significant ECA effects are considered likely.

2. Unlike other areas to the north in the Thompson and Cariboo, young 20 to 30 year old regenerating pine standsin Hydraulic Creek do not appear to have been attacked by MPB. If widespread attack should occur in thesestands it would alter watershed ECA recovery projections, and increase potential hydrologic risks.


36

However as discussed in Section 2.0, ECA only describes the hydrological effects on snowaccumulation and melt due to forest canopy changes, and an ECA hazard value alone is notnecessarily a good indicator of actual watershed hydrological hazards. In Hydraulic CreekWatershed the intensive management of runoff through flow diversions and relatively largereservoir storage has such a significant effect on watershed response disturbances (as discussedbelow in Section 3.2.5.) that overall watershed ECA effects are not considered meaningful.The McCulloch Reservoir substantially alters the hydrological effects of runoff from the upperMcCulloch Basin on the lower Hydraulic Residual basin. In the following analyses, sub-basinhazards are first considered separately. Then analyses of hydrologic effects in the lowerwatershed, including at the SEKIDS water intake, considers how the reservoir mitigatescumulative hydrologic effects.

3.2.3 Sub-basin ECA Scenarios

In addition to the total watershed ECA hazard analysis above, analyses of ECA scenarios werecompleted for the Fish Creek, McCulloch Reservoir Residual and Hydraulic Creek Residualsub-basins (see Figure 1).

0

10

20

30

40

50

60

0 10 20 30 40 50 60

MPB/UnharvestedCC Harvested

Figure 10. ECA progression curves for Fish Lake sub-basin, a 419 ha area with severalreservoirs that drains into Hydraulic Creek downstream of McCulloch Reservoir.

Low

Moderate

High

Very High


37

0

10

20

30

40

50

60

0 10 20 30 40 50 60

Year

EC

A(%

)

CC Harvested

MPB/Unharvested

Figure 11. ECA Progression curves for the upper watershed areacontributing to the McCulloch Reservoir sub-basin peak flows.

0

10

20

30

40

50

60

0 10 20 30 40 50 60 70

Years

EC

A(%

)

Low

Moderate

High

Very High

MPB/Unharvested

CC Harvested

Figure 12. ECA Progression for Hydraulic Residual which is the lower watershed areacontributing runoff to Hydraulic Creek mainstem below the McCulloch Reservoir.

Low

Moderate

High

Very High


38

From these curves it can be concluded that:

In the 4343ha McCulloch basin in the upper watershed above McCulloch Reservoir,current ECA levels are moderate, and extensive recovering older clearcuts willoutweigh MPB canopy effects in pine-leading stands over time. Following totalpine mortality there will be no increase in ECA, which will slowly continue todecrease over time, and the long-term sustained ECA MPB-related hazard will bemoderate for about 25 years. That is, ECA effects may or may not be noticeable;and if noticeable will be small. Without MPB infestation ECA and hydrologicrecovery would be faster. With total harvest of pine-leading stands there will be a15 year period of sustained high ECA hazard, where significant ECA effects areconsidered likely; and a 25 year period of moderate to high ECA effects.

In the small 418ha Fish Creek residual the current ECA is 40%, which is consideredhigh. Extensive recovering older clearcuts will outweigh MPB canopy effects inpine-leading stands and the ECA will continue to decrease. ECA hazard levels willbe mostly moderate for about 25 years. Following full salvage harvest the ECAwill increase and remain high for about 18 years, also decreasing to low in about 25years.

In the 4618ha Hydraulic Residual, which is the lower watershed downstream ofMcCulloch Reservoir and above the SEKIDs water intake, the current ECA value(~30%) is moderate. Following pine mortality the ECA hazard will graduallydecrease through the moderate hazard range to low, in about 20 years as numerousolder harvested and planted stands regrow. Full salvage harvest of pine-leadingstands will result in an increase in ECA hazard into the high range for less than adecade, after which it will also decrease through the moderate range to low in about20 years.

3.2.4 Flood frequency shift

The changes in forest canopy closure represented by ECA result in increased snowaccumulation and freshet snowmelt rates, which in turn can result in an increased frequency offloods of any particular magnitude, which is know as the flood frequency shift.

Spring peak flow generation in nival watersheds is a complex process involving snow pack,forest cover, microclimatology and weather. This study uses the results of numerical modellingwatershed studies for 11 nival, unregulated Interior B.C. watersheds, which look at changes inflood frequency following widespread watershed forest cover disturbances (Alila, et al. 2007,FPB 2007, Schnorbus et al. 2004). That is, computer models of watershed processes are usedto predict changes in flood frequency following modelled changes in forest cover conditions inthe study watersheds. Appendix D-Flood Frequency Analysis provides details of that analysis.


39

Pearson Creek Flood Frequency

0.00

5.00

10.00

15.00

20.00

25.00

30.00

1 10 100

Return Period (Years)

Me

an

An

nu

alD

aily

Flo

od

(m3/s

)

Figure 13. Estimated flood frequency shift mid-sized Okanagan Watersheds with a high ECA hazard.

Figure 13 is a conceptual analysis of the expected change in flood frequency in an “average”mid-sized (10’s to 100’s km2) Okanagan watershed, given a high ( 50 to 70%) ECA. In thiscase Pearson Creek is used, and the results for a high ECA value extrapolated from Alila et al.,2007). Like Hydraulic Creek, Pearson Creek is a tributary of Mission Creek and has a longenough stream discharge record to generate a meaningful flood frequency curve. UnlikeHydraulic Creek, it is an unregulated watershed, with no flow restrictions or significant lakestorage.

As shown in Figure 13, with a high ECA imposed on the watershed, the historic 50 year floodis expected to occur approximately every 20 years; and all other magnitude floods wouldsimilarly be expected to occur more frequently. This kind of flood frequency shift is expectedfor less than a decade in the Hydraulic Residual area above the SEKID intake, following totalsalvage harvest of pine leading stands. With a moderate ECA, such as that expected for lessthan 20 years in Hydraulic Residual after total MPB pine mortality, a noticeable increase inflood frequency, and shift in the flood frequency curve, may or may not occur, and if it does itis expected to be small.

It is important to remember that the above analysis is based on research in unregulated InteriorB.C. watersheds. Watershed characteristics, including lakes, reservoirs and inter-basin watertransfers can significantly alter the likelihood of ECA hazard effects resulting in peak flow andhydrological hazards, as discussed below.

Pearson Ck.1961 to 1993

High (35 to 50%) ECA

5020


40

3.2.5 Watershed Reservoir Management and Flood Regime

Water supply reservoirs on Hydraulic Creek are managed by SEKID throughout the year. Theprimary flow control and storage reservoir is McCulloch Reservoir, which is comprised ofseveral lakes including: Hydraulic Lake (Photo 1), Minnow Lake and Haynes Lake.McCulloch Reservoir has a capacity of 16.62 million m3 (13,475 AF). The reservoir systemgenerally fills every year and when full, overflow is spilled into Idabel Lake via Pear Lake,which is located in the Wilkinson/West Kettle River drainage. The McCulloch Reservoircontrol outlet to Hydraulic Creek was fully automated in 1996. A minimum flow of 0.013m3/shas been assigned to Hydraulic Creek for fisheries purposes during the low flow season.

Hydraulic Creek has a number of diversions into and out of the watershed including:

Pooley Creek/KLO Creek diversion: Water from the Pooley/KLO Creek watershed isdiverted into Hydraulic Creek. Gates on Pooley and KLO Creek are manually openedto divert flows from these streams into Hydraulic Creek as soon as access is possible inthe spring, usually late March. Diversion structures on the creeks convey water toHydraulic Creek via a cross-slope diversion ditch, which also captures slope runofffrom smaller streams and tributaries. The diversion weirs have a spillway and overflowinto their respective streams when capacity of the diversions are exceeded. Water fromthese streams is diverted into Hydraulic until June 30. In a 1979 Ministry ofEnvironment report it was suggested that Pooley Creek contributes the largestproportion of runoff to the McCulloch Reservoir, and that nearly 40% of the meanannual runoff from the Hydraulic Creek drainage area was derived from areas drainingto both the Pooley and Stirling Creek diversions (Dobson 2003, MoE 1979).

Myra/Canyon Creek diversion: Water from the Canyon and Affleck Creek watershed isdiverted into upper Hydraulic Creek on a permanent basis.

Turtle Lake reservoir and diversion: Water is diverted from Sterling Creek, andsometimes Hydraulic Creek, to fill the newly expanded Turtle Lake reservoir, which sitswithin the headwaters of Affleck Creek. Turtle Lake will fill over the next 2-3 years.At capacity, water will spill into Hydraulic Creek.

Browne Lake diversion: Browne Lake, in the upper Fish Lake sub-basin has a spillwaystructure into Mission Creek and a gate that may divert water out of the Fish/Hydraulicwatershed directly into Mission Creek during periods of poor water quality. Forexample, in the low water conditions of 2003, water from Browne Lake exhibited highcolour values and was diverted into Mission Creek. Otherwise, water flows from LongLake into Browne Lake, which flows into Fish Lake and then into Hydraulic Creek viaa culvert that passes under the Wardlaw Homestead, downstream of McCullochReservoir.

Figure 14 shows the effect of this extensive reservoir management, by comparing measuredMay 1976 to July 1981 stream flows at the outlet of McCulloch Reservoir (blue line) anddownstream below the SEKIDS water intake (purple line), near the mouth of Hydraulic Creekat Mission Creek (WSC, 2009). It illustrates typical operations of the Hydraulic Creekreservoirs and water use (pers. comm. Toby Pike, P.Eng. SEKID).


41

Hydraulic Creek Flow Comparison - May 1976 to July 1981

0

0.5

1

1.5

2

2.5

01/01/76 01/01/77 01/01/78 01/01/79 01/01/80 01/01/81

Date

Dis

ch

arg

e

Hydraulic Creek Near the Mouth (08NM010) Hydraulic at McCulloch Outlet (08NM011)

Figure 14. Stream flow hydrographs for Hydraulic Creek at the outlet of McCulloch Reservoir and nearthe mouth of Hydraulic Creek downstream of the SEKIDS water intake, between May 1976 and July 1981.

According to Figure 14, discharge near the mouth typically peaks in May around 2 m3/s. Therelittle or no release from the reservoir or withdrawals at the SEKIDS intake as irrigationdemands are low. Therefore these peaks represent the natural spring runoff from the areadownstream of the reservoir, defined in this study as the Hydraulic Residual.

From early June through September there are large releases from the reservoir; howeverdischarge below the SEKIDS intake is small (shown by the pink line), as most reservoirdischarge is withdrawn at the intake for agricultural and other uses. Assuming no other losses(e.g. infiltration to groundwater), peak demand during the June through September growingseason for this period appears to be around 1.4 to 1.5 m3/s.

Using a regional analysis one can estimate expected flood levels if watershed discharge wereunregulated; that is without the extensive artificial reservoir storage. The total naturaluncontrolled drainage area for Hydraulic Creek is approximately 87.5 km2. Using regionalisolines from BC Streamflow Inventory Mapping, a 100 year return period peak flow for awatershed of this size would be 22.5 m3/s (Coulson 1998). Natural stream channel capacity istypically assumed to be approximately equal to the mean annual flood discharge (Leopold et.al. 1964). Assuming a peak flow ratio Q100/Q2 of 2 or 3 to 1, a natural mean annual (Q2) peakflow for unregulated flow in Hydraulic watershed would be in the range of 7.5 to 11 m3/s(Beckers et.al. 2002).


42

Measured annual peak flows in lower Hydraulic Creek range from 2 to 4 m3/s (Figure 14 andDobson 1998), well below the expected unregulated discharge. Clearly flow management asshown in Figure 14, has substantially reduced peak flows in lower Hydraulic Creek and thechannel has excess natural capacity. Also based on Figure 14, it can also be assumed thatcurrent peak flows in Hydraulic Residual mainstem are largely the result of runoff from thewatershed area below the reservoir.

3.3 HYDROLOGIC HAZARD

3.3.1 Peak flow hazard

Peak flow hazard is the potential or likelihood that a sub-basin will develop an elevated flowregime following changes in forest cover. Prime factors when considering peak flow hazardsare the extent of forest canopy loss (ECA) discussed in earlier sections, and the routingcharacteristics of the affected sub-basin (See Figure 2). Sub-basin factors that affect runoffsensitivity include steepness, soil drainage properties, drainage density, soil depth (or proximityto an impervious layer), and existing storage such as reservoirs, lakes, and wetlands. HighECA in a sub-basin with rapidly routed runoff and little opportunity for storage will result in ahigh likelihood or potential for increased peak flows. A lower ECA and/or opportunities forsignificant water retention in lakes and reservoirs will reduce peak flow hazards.

Table 6 presents peak flow hazards for each sub-basin and the Hydraulic watershed as a wholeunder the two forest management ECA scenarios of ‘MPB/unharvested’ and ‘Full-salvage’.ECA curves for the two management scenarios are shown in Section 3.2.3 and ECA hazards inTable 6 are represented by the maximum ECA value over time. Reservoir storage and releasefactors affecting peak flows for sub-basins are discussed in Section 3.2.5. Sub-basin peak flowattenuation potentials are described as ‘Poor’ (not likely to attenuate peak discharge),‘Moderate’ (some potential to attenuate peaks) and Good (likely to significantly attenuate peakflows). Combining ECA hazards with sub-basin response gives a peak flow hazard rating.Where poor peak flow attenuation is anticipated in a sub-basin, ECA-related increases in runofftranslate directly into increased flow regimes. Moderate or good attenuation will result in PeakFlow hazards one or two levels respectively less than the ECA hazard.

Table 6. Peak flow hazard ratings derived from sub-basin routing characteristics and ECAlevels

*Hydraulic Residual Tributaries are discussed separately below.

ProjectedMaximum

ECA(Percent)

SustainedECA

HazardLevel

ProjectedMaximum

ECA(Percent)

SustainedECA

HazardLevel

Peak FlowHazard

Sub-basin

Peak FlowAttenuation

Potential MPB Full Salvage MPBFull

Salvage

McCullochGood 28 M 52 H VL L

Fish LakeGood 40 M 50 H VL L

Hydraulic ResidualMainstem*

Good 29 M 40 M-H VL L


43

ResultsWithin the McCulloch basin there is good peak flow attenuation due the low gradient and smalllakes and wetlands. The Fish Lake basin has high proportion of lake area relative to the smalldrainage area. The good peak flow attenuation will reduce the expected ECA hazard effect inboth these basins so that the MPB and full harvest scenarios have very low and low Peak Flowhazards respectively.

In the Hydraulic Residual there is poor attenuation of peak flows in the tributaries, however thetributaries have a relatively small peak flow and sediment mobilization effect compared to themainstem, which has very good peak flow attenuation from the McCulloch Reservoir.Therefore the overall peak flow attenuation is considered good and in the lower HydraulicMainstem there is a very low to low peak flow hazard for the MPB and full salvage harvestscenarios respectively.

While the overall extent of expected forest cover disturbance (ECA) is not high for very long ineither management scenario in Hydraulic Residual, it is concentrated in the upper drainageareas of small tributaries on the south side of the valley, largely due to the 2003 OkanaganMountain wildfire and post-fire salvage. The lower reaches of Hydraulic Residual tributarieswere not visited in the field. Although no sign of disturbance was noted in a helicopter fly-over, it is possible there could be small sediment sources on the steeper lower valley sidewallsof these small streams that would be sensitive to increased peak flows due to forest coverdisturbance within their headwaters.

3.3.2 Hydrologic hazard

Hydrologic hazard represents the potential or likelihood of peak flow or sediment impacts toexisting channel systems in response to the projected change in flood regime. Hydrologichazard ratings are derived from channel sensitivities (Table C-2) and peak flow hazard ratings(Table 6), which are combined using a standard risk matrix (see Appendix A, Table A2). Table7 shows the resulting Hydrologic Hazard values for each of the Hydraulic Creek sub-basins.

Table 7. Hydrologic Hazards by Sub-basin

In the upper watershed, assuming the design capacities of the control system structures are notexceeded, and excess freshet flows at diversion sites continue to be spilled into anotherwatershed, there is a generally a very low likelihood of increased peak flows and increasedsediment delivery in the McCulloch and Fish sub-basins.

Peak Flow Hazard(from Table 6)

Hydrologic Hazard(Peak Flow Hazard Combined

with Channel Sensitivity)

Sub-basin

ChannelSensitivity

(from Table 5) MPB Full salvage MPB Full Salvage

McCulloch L VL L VL VL

Fish Lake L VL L VL VL

Hydraulic ResidualMainstem

M VL L VL L


44

In the Hydraulic sub-basin mainstem channel sensitivities are generally low to moderate (SeeSection 3.1.3). When combined with the very low to low peak flow hazards for the MPB andfull salvage scenarios respectively, the hydrologic hazards are very low (See Table A2,Appendix A).

In the lower mainstem reaches above the SEKIDS intake, following MPB attack and pinemortality there will be a very low Hydrologic Hazard, or a very low likelihood of noticeablepeak flow and/or sediment effects at the SEKIDS intake. With the full pine salvage scenariothere is a low likelihood of noticeable peak flow and sediment effects.

As noted above, the concentration of forest cover disturbance may lead to local effects in thesmall tributaries in the Hydraulic Residual. A ground investigation of these tributaries wouldincrease the level of certainty regarding their condition and the likelihood of sedimentmobilization to the mainstem from these steeper channels.

It is interesting to note that the Hydrologic Hazard conclusions for the Hydraulic Residualimplies that current turbidity problems at the SEKIDs intake do not appear to be related to highpeak flows or to excessive sediment sources in the lower channel or tributaries, beyond thesingle landslide and minor bank erosion observed. This suggests that a significant part of theturbidity problem is likely due to organic particles and colour, which usually originate inwetlands and reservoirs.

3.3.3 Low flow hazard

It is widely accepted that clearcutting increases annual water availability, growing season soilmoisture and potentially stream flows; because removing the trees decreases interception andevapotranspiration water losses associated with the forest. The effect of MPB mortality andsalvage is expected to be similar. A literature review and workshop attended by most researchforest hydrologists in B.C. to address low flow issues in Interior B.C. snowmelt dominatedhydrologic regimes, such as Hydraulic Creek, concluded that; “Forest management generallyincreases water volume - no case studies relevant to snowmelt-dominated regimes reported adecrease in water quantity as a result of forest harvesting” (Pike and Scherer, 2003). Thelikelihood of MPB mortality and salvage negatively affecting unregulated growing season lowflow stream discharges in Hydraulic Creek is considered low.

However widespread removal of forest cover can also expose the melting spring snow pack togreater energy inputs, causing it to melt faster so that the freshet melt and associated peak flowsoccur earlier. This shift in the hydrograph can necessitate earlier use of reservoir storage andtherefore earlier reservoir depletion later in the growing season. Figure 15 shows this effect asmodelled in another Okanagan Watershed, Trout Creek, which does not have anywhere nearthe storage capacity that Hydraulic Creek does, relative to total basin size. It shows that anearlier water demand (the yellow line representing 1987 conditions, when reservoir drawdownbegan approximately 30 days earlier than in normal years shown by the black and red lines),will require greater reservoir drawdown, and increasing restrictions on water use. BecauseHydraulic Creek has greater relative storage than Trout Creek, the effect of earlier drawdownon later season water restrictions is not expected to be as large as shown in Figure 15. But asignificant advance in freshet timing and the start of reservoir drawdown could affect lategrowing season supplies to some degree in Hydraulic Creek.


45

Figure 15. Trout Creek annual storage hydrograph for select years (coloured lines), with water usemanagement stages (coloured blocks). With the lower storage volume stages (increasing numbers 2

through 5) there are increased water use restrictions. (From Aqua Consulting Inc., 2008).

To estimate what effects the expected MPB and salvage ECA values (Figure 9) could have onfreshet timing and reservoir drawdown, the results of 24 paired-watershed and numericalmodelling studies of the effects of forest disturbance (harvest, fire, MPB) on earlier peak flowswere reviewed (Pike and Scherer 2003, Alila, et al. 2007 and FBP 2007).

There was a large variability between study watershed sizes and conditions, forest disturbanceor treatment and in the resulting measured freshet timing, which was between 0 and 20 daysearlier in treated or disturbed watersheds than in control watersheds. There were also largedifferences in annual freshet timing within an individual study. For instance Alila et al. (2007)found that in Whiteman Creek their model predicted that over the 76 years of simulatedclimatic record the average freshet advancement over the control was 4 days. Howeverindividual annual freshet timing varied from 2 days later to 40 days earlier. Our conclusion isthat this is an area that requires more study, and there is too great an uncertainty around studyresults to extrapolate from them to Hydraulic Creek, other than to say that:

The forest cover disturbance caused by the full salvage harvest scenario, and hencepotentially freshet advancement, would be greater than the effect of MPB mortalityand the no harvest scenario (see Figure 9).

If there will be any noticeable effect it will be to advance freshet timing. However,because or the extensive inter-basin flow routing and reservoir storage, for eitherscenario this effect is expected to be relatively small, and would not significantlyaffect reservoir storage in the later growing season.


46

3.4 CLIMATE CHANGE

The Okanagan Basin Climate Change Study projects an increase in temperature of about 1oC inall months by 2020 (WMC, 2005). This will have two major effects on SEKID water demandand supply.

There will be increased agricultural demand. With each increase of 1oC it is estimated totalirrigation demand will increase by 10% from April through October. Higher temperatures willalso result in earlier snowmelt and annual spring hydrograph peak. Figure 16 shows theexpected change in freshet hydrograph in Camp Creek, an unregulated 34km2 OkanaganWatershed draining into Trout Creek, about 50km southwest of Hydraulic Creek. Springsnowmelt and freshet are advanced about 20 days. (WMC, 2005).

As discussed in Section 3.3.3 earlier spring runoff results in earlier storage hydrographrecession, earlier use of reservoir storage, earlier reservoir drawdown and less available storedwater supply in the latter part of the growing season.

The magnitude of the combined effects of climate change-related increased demand and earlierstorage depletion are not known. Because Hydraulic Creek watershed has large reservoirstorage relative to basin size, the risk of late growing season water availability is less than inmany other Okanagan watersheds. Nonetheless, in time climate change temperature increasescould be greater than 1oC. And since these effects will likely be cumulative with natural annualclimate variability in freshet timing, and with MPB and salvage harvesting effects, in someyears there could be serious impacts to late growing season water supplies in Hydraulic Creek.

Figure 16. Projected climate change impact on freshet peak timing in unregulated flowsin Camp Creek with a 1oC temperature increase predicted by 2020 (From: WMC, 2005).


47

3.5 WILDFIRE

Concerns have been raised about increased risks of wildfires and severe wildfires in stands andwatersheds where there is widespread MPB mortality, presumably because dead pine trees areseen as increased fuel load relative to live pine stands. Extensive wildfire, and locally severewildfires can create changes in the hydrological functioning of forests, and increase flood andother hydrogeomorphic risks to downstream values (Scott and Pike, 2003).

It has been noted, in a study of fire occurrence and effects in MPB attacked and non-attackedstands in Colorado, that: “Although it is widely believed that insect outbreaks set the stage forsevere forest fires, the few scientific studies that support this idea report a very small effect, andother studies have found no relationship between insect outbreaks and subsequent fire activity.Based on current knowledge, the assumed link between insect outbreaks and subsequent forestfires are the norm . . . is not well supported, and may in fact be incorrect or so small an effect asto be inconsequential for many or most forests” (Romme et al. 2007).

The reason proposed for this finding is that weather may be a more important factor than standcondition, and where drought has increased the fire hazard in all stands, both live and deadfuels will carry fire (Romme et al. 2007). In lodgepole pine stands in the 1988 Yellowstonefires, Lynch (2006) found that MPB-affected areas had only an 11% higher probability ofburning compared to un-infested areas.

There is some agreement that for the one to two-year period following attack, when the treesstill retain their needles, there is an increased crown fire hazard. After the needles have fallen,the risk of crown fire and fire behaviour potential is reduced for one to several decades. Firerisk may then return to pre-fire intensity levels as dead trees fall and fast growing understoryvegetation provide fuels. (Romme et al. 2007; Duffy, C.D., Superintendent, Fuel Management,Fire Management Section, Protection Branch, MoF, Victoria, pers. comm. 2008).

Presumably for these reasons, advice to the Chief Forester of BC Forest Service regardingMPB-related salvage harvesting has been: “Increased risk of fire in MPB-affected stands hasbeen postulated by many, but evidence in the literature is equivocal (e.g., Turner and Carroll1999). Conducting salvage operations based on the premise of reducing fire risks is notrecommended, except in the wildland-uban interface” (Eng 2004). We agree with thisstatement and recommend that, except in the wildland-urban interface, and possibly in smalltributary watersheds (<10km2) with high property or infrastructure values on the fan,widespread salvage of MPB attacked stands should not be carried out if the managementobjective is to reduce fire risk.

4.0 CONSEQUENCES

4.1 Water Quality and Infrastructure

Hydraulic Creek is the current primary supply source of irrigation and domestic water to theSouth East Kelowna Irrigation District which supplies water to 2400 ha of serviced agriculturalland, through approximately 2000 domestic, 420 agricultural, and 25 commercial andinstitutional connections (Associated Engineering, 2007). As discussed in Section 3.2.5 thereare numerous complex water diversions into and out of the Hydraulic Creek watershed toaugment summer low flows and to spill excess flows when reservoirs reach full capacity.


48

Water released from reservoirs is diverted from Hydraulic Creek at the intake site, locatedabout 12km downstream of the outlet of McCulloch Reservoir, where there are two settlingponds and a balancing reservoir, with rotating screens to remove large debris, and chlorinationat the point of entry into the distribution system.

As discussed in Section 2.4.1, the water quality parameters most-strongly linked to MPBinfestation and/or salvage harvesting are those related to fine and coarse sediment production.Because turbidity and colour values frequently exceed IHA guidelines, SEKIDS is exploringother options for treatment or separation of agricultural and domestic delivery systems, andalternate sources of domestic supplies. It is not known for certain how the domestic watersupply issue will be resolved, or how much high turbidity values are due to fine sediment andhow much to organic sources (see Sections 2.4.1). For the near future Hydraulic Creek willremain the main domestic as well as agricultural supply and increased fine sediment delivery tothe SEKID water intake will have serious consequences.

There is no information indicating coarse sediment delivery has been a serious problem toSEKID water supply infrastructure. This is likely due to the relatively low incidence oflandslides and other significant sediment sources in the lower watershed, the extensivereservoir sediment sinks in mid-watershed, and the watershed peak flow attenuation by mid-watershed reservoirs, and the two settling ponds above the intake. Nevertheless, and increasein coarse sediment delivery due increased peak flows and mainstem or tributary channelerosions, or landslides on the steep valley sidewalls of lower reaches, could cause increasedmaintenance costs for District.

At the request of IHA this study looks only at the flooding and sediment hydrologic hazardsthat could impact a sufficient and reliable supply of safe and aesthetically acceptable water atthe DoS water intake, which is considered the consequence in a partial risk analysis. Thevulnerability or other details of the DoS water supply and treatment system are not consideredhere.

4.2 WATER SUPPLY

With the addition of the Turtle Lake Reservoir, natural watershed runoff, flow diversions intoHydraulic Creek, and the large reservoir storage capacity are expected to meet projectedagricultural and domestic demand for the next decade (Associated, 2007). Nonetheless, anydecrease in the capability of available storage to meet that demand would be considered a highconsequence.

4.3 FISH

Sportfish species within the watershed include Brook Trout (Salvelinus fontinalis) andRainbow trout (Oncorhynchus mykiss). All lakes are known to contain fish with the exceptionof Long Meadow Lake and Weddle Lake, therefore fish presence is considered likelythroughout the watershed despite barriers to upstream fish migration.

Hydraulic Creek fish presence and habitat values for all reaches are presented in Appendix D,along with a fish consequence ranking for that reach, based on criteria presented in Table 2(Section 2.4.3).


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Figure 17 summarizes fish habitat consequence ratings for each macro-reach. In general, fishhabitat is widespread through the watershed, mostly due to naturally and/or artificially stockedlakes on the upper plateau. Moderate to High fish habitat consequence ratings have beenassigned for most mainstem channels and lakes. Exceptions are Long Meadow, Knox, Weddleand Acme Lakes, which were assigned a low rating due to limited potential for over-wintering.Steep gradients along tributaries in the Hydraulic Creek Residual sub-basin resulted in a VeryLow fish habitat consequence rating.

4.4 SOCIAL INFRASTRUCTURE

Social infrastructure in the Hydraulic Creek watershed (other than the community intake andcontrol structures) include: agricultural development, the Kettle Valley Railway trail (KVR),logging road bridges and other private crossings (farm bridges). Private water licenses fordomestic and irrigation use are listed on Pear and Knox Lakes and a domestic license is underapplication on Browne Lake. Intakes on lakes tend to be less sensitive to minor changes inflow and sediment.

Some land adjacent to Hydraulic Creek was historically cleared for agriculture, including theWardlaw homestead. Gradients are low through this section and soils are high in peat. Thecreek was channelized through the Wardlaw meadows to improve water quality in the early1980’s. At least one farm access bridge and two footbridges exist over Hydraulic Creek in thisarea. Farm Bridges were not inspected in Hydraulic Creek; however these structures are oftenhave limited capacity and can be vulnerable to significant increases in peak flows or debrismovement.

The KVR crosses Hydraulic Creek downstream of Wardlaw meadows in a 2 x 1.4 m concretebox culvert constructed in 1948 (Photo 8), beneath a large embankment. There is no evidenceto suggest a lack of capacity for the controlled discharge from McCulloch Reservoir.

KVR crossings of Hydraulic Creek tributaries were inspected and cross drainage is provided byculverts, some recently upgraded. Where the KVR crosses upper Myra Creek, a tributary ofHydraulic, no culvert was found. Drainage appeared to pass through coarse angular material inthe sub-grade, which may contain a buried culvert. Although this arrangement appears to havefunctioned for many years, it may be sensitive to potential increases in flow related to MPB.Sections of the KVR adjacent to Hydraulic Lake may be vulnerable to flooding if freshetspilling could not keep up with reservoir inflow, which is considered unlikely.

There are several logging road bridges over the Hydraulic Creek mainstem upstream ofHydraulic Lake (Photo 9). Deactivation of roads not in use was observed (i.e. culverts removedand replaced by fords or cross ditches). Detailed analyses of all existing crossings were notconducted. Culverts observed on active mainlines crossing tributaries appeared adequate forexisting conditions; i.e. pre MPB infestation. Therefore there is a moderate vulnerability toincreased flows due to MPB and salvage


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Photo 8. Hydraulic Creek mainstem below McCulloch Reservoir, beneath fillembankment supporting KVR bicycle path /TransCanada trail.

Photo 9. Hydraulic Creek mainstem/forest road crossing above McCulloch Reservoir.


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Table 8 outlines the assumptions used to develop infrastructure vulnerability ratings. Theseratings represent an assumed general vulnerability based mostly on past performance ofstructures during historic floods.

Table 8. Social Infrastructure Vulnerability RatingItem at Risk Key Issues Comments Vulnerability

RatingPrivate Water Licenses Rapid filling/drawdown of

reservoirs, flooding, waterquality (e.g. sediment, algaeblooms)

Lake intakes are generally set at gooddepth away from shore. Sedimententering lakes will likely settle awayfrom intakes.

L

Forestry Road Crossings Increased peak flows,increased scour, increaseddebris movement.

Mainstem crossings with adequatebridges. Tributary flows notattenuated by storage. Crossingsadequate for current conditions willbe somewhat vulnerable to increasedflows.

M

KVR- Trans-Canada Trail Mainstem culvert capacityunder high embankment.Channel instability scourand/or debris movement alongtributaries. Flooding adjacentto Hydraulic Lake.

Culvert under mainstem/ KVR hasfunctioned well for at least 60 years.With the exception of Myra Creek,tributary crossings have adequatedrainage capacity with someupgraded and some culvertsupgraded. Debris movement unlikelyat mainstem crossing site (meadowsand reservoir upstream). Spillwayshistorically able to prevent floodingof trail adjacent to McCulloch.

L

Private/Farm Bridges Increased peak flows,increased scour, increaseddebris movement.

Often under-designed and/or under-constructed. Abutments frequentlyencroach on channel, subject to scour.Low clearances.

H

5.0 RISK ANALYSIS

5.1 WATER QUALITY AND INFRASTRUCTURE

Table 9 summarize the partial risk analysis for water quality at the SEKID water intake. Thehydrologic hazard, which includes both incremental peak flow and channel erosion sedimenthazards, is taken from the Hydrologic Hazard ratings for Hydraulic Residual (Table 7) whichhas the SEKID intake at the lower end of Reach 1.

Table 9. Partial risk analysis for SEKID water intake.

Hydrologic Hazard(peak flow and

sediment)

Water Quality Element at Risk:SEKID Water Intake

Partial Risk

Reach

MPBFull

SalvageFine sediment

CoarseSediment

MPBFull

Salvage

HydraulicResidual

(Reaches 1-4)

VeryLow

Low

less aesthetic appeal,more microbiologicalactivity, less effective

primary treatment

Intake damage,maintenance

VeryLow

Low


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For the MPB infestation scenario (with no salvage harvesting) there is a low peak flow hazardand coarse and fine sediment risk to water quality and infrastructure at the intake. In otherwords, with full MPB-related pine mortality little or no discernable increase in peak flows andassociated fine and coarse sediment at the SEKID intake is expected. With the full salvage ofpine-leading stands scenario there is a moderate risk of increased peak flows and associatedfine and coarse sediment delivery to the SEKID intake. That is, there may or may not be adiscernable increase in peak flows and sediment to the intake, and if there an effect it isexpected to be small.

5.2 WATER SUPPLY

The consequence of potential decreases in later growing season water storage availability dueto earlier use and drawdown of Hydraulic Creek reservoirs is considered high. There is a highdegree of uncertainty as whether or how much MPB and salvage harvest-related changes inforest cover will advance spring freshet timing, which could cause an earlier start to reservoirdrawdown, and ultimately greater reservoir depletion in the later growing season. While theexpected freshet advancement due to MPB pine mortality is not expected to be large, becauseof the relatively low forest cover disturbance expected, it will be greater with the full harvestscenario, which will cause increased forest cover and ECA effects (Figure 7). However thelarge reservoir storage relative to watershed size will likely mitigate both MPB and salvage-related freshet timing changes, so that it is considered unlikely that significant or noticeableeffects will occur with either scenario. Therefore the MPB-related risk to water supplies inHydraulic Creek is considered low.

As discussed in Sections 3.4, a much greater change in freshet timing, and risks to watersupplies, is expected due to global climate change-related temperature increases, depending onthe amount of temperature increase that occurs in the Okanagan.

5.3 FISH

For each tributary reach, hydrologic hazards (Table 7) are combined with the fish consequencevalues (Appendix C, Table 2) using a standard risk matrix (Appendix A), to arrive at the fishhabitat risk ratings in Table 10.

Note that risks to fish values only occur where fish populations and habitat exists and this riskrating may not represent the entire sub-basin. Since hydrologic hazard is generally cumulativeto the downstream end of the sub-basin, risk ratings in tributary basins generally represent risksnear the lower end of the sub-basin. Risks in residual sub-basins represent risks to habitatvalues along the Hydraulic Creek mainstem. The extent of fish habitat along tributaries in theHydraulic Residual sub-basin is likely minimal given their small, steep nature.


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Table 10. Risks to Fish Values by Sub-basin

Hydrologic Hazard(From Table 7) Risks to Fish habitat

Sub-basin Name MPBFull

Salvage

FishConsequence

Rating MPBFull

Salvage

McCullochVL VL H L L

Fish LakeVL VL M L L

Hydraulic Residual (Reaches1-5)

VL L H L M

In both the upper sub-basins, there are low risks to fish habitat following both the MPB/nosalvage and the full salvage scenarios. This reflects the fact that the conditions in the lakes,where most of the habitat exists, are not likely to change under either scenario.

Due to flow attenuation in the lower Hydraulic Residual sub-basin, there is a very low to lowhydrologic hazard with the MPB/no salvage and full salvage scenarios respectively. Whencombined with the high fish habitat values found in portions of the lower mainstem, there is alow to moderate risk of degradation to the fisheries resource. Outflows from the reservoir intothe mainstem are not likely to change; however it is possible impacts to fish habitat could resultfrom increases in sediment delivery from the steeper tributaries found in the HydraulicResidual sub-basin.

5.4 SOCIAL INFRASTRUCTURE

Hydrologic hazard is combined with infrastructure vulnerability ratings presented in Table 7 togenerate the infrastructure risk ratings summarized in Table 11.

As noticeable increases to peak flows and sediment mobilization are not anticipated anywherein the watershed as a result of MPB or salvage harvesting, all the risk ratings are very low orlow.

Forestry road crossings of the upper mainstem and tributaries are shown as low risk. Forestlicensees, Ministry of Forest and Range and other road permit holders should regularly inspectand maintain crossings in all areas of this community watershed, upgrade crossings if necessaryand deactivate those no longer in use with a failsafe design.

Although farm bridges are typically vulnerable to damage by high water, no significant changein peak flows is anticipated downstream of the reservoir, and there is a low likelihood ofsignificant impacts occurring.


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Table 11. Social Infrastructure Risk RatingsHydrologic

HazardInfrastructure Risk

Ratings

Item at Risk

ConsequenceVulnerability

Rating MPBFull

Salvage MPBFull

SalvagePrivate waterLicenses (McCullochand Fish Lk. sub-basins)

L VL VL VL VL

Forestry Roaddrainage structures(upper sub-basins)

M VL VL L L

KVR /Trans-CanadaTrail(Hydraulic Residual)

L VL L VL VL

Private/Farm Bridges(Hydraulic mainstem,Reach 5)

H VL VL* L L

* Reach 5, the upper gentle gradient reach in the lower Hydraulic mainstem has a lower channel sensitivity, andhence a lower hydrologic hazard (very low), than the moderate channel sensitivity of Reaches 1 to 4, which givethis sub-basin its generally low hydrologic hazard rating (See Figure 7).

6.0 CONCLUSIONS AND RECOMMENDATIONS

6.1 CONCLUSIONS

The water quality parameters most strongly linked to MPB infestation and salvage logging inHydraulic Creek watershed are increased peak flows (floods) and associated mobilization offine and coarse sediment from stream channel beds and banks. The effects of forest canopyremoval from pine mortality and/or harvesting result in moderate to high ECA hazards for theMPB/no salvage and the full pine-leading stand salvage scenarios respectively, with maximumECA values of approximately 50%. However the good attenuation of upper watershed runoffand peak flows by the McCulloch Reservoir, and the low to moderate channel sensitivitiesthroughout result in very low to low hydrologic hazards in watershed, following eithermanagement scenario.

The low hydrologic hazard ratings result in a very low to low risk of increased peak flows andassociated increased fine and coarse sediment at the SEKID intake, following the MPB/noharvest and the full salvage harvest scenarios respectively. That is, following the completemortality of all pine and with no further harvesting in Hydraulic Creek watershed, there is avery low risk of hydrologic impacts to the SEKIDS water intake. If all pine-leading stands inthe watershed were harvested there would be a low risk of hydrologic impacts. Therefore nonoticeable increased flooding or sediment effects are expected at the intake, following eitherscenario. However, turbidity levels have been and will continue to present problems at theSEKIDS water intake, in terms of meeting Interior Health Authority water quality guidelines;such that alternative sources of domestic drinking water supplies are being explored. The verylow to low hydrologic (flood and sediment) hazards suggest that a significant part of theturbidity problems are likely due to organic particles and colour, which usually originate inwetlands and reservoirs.


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Similarly, significant advancement of freshet timing at the SEKID water intake is not expectedfollowing the MPB/unharvested scenario or the full salvage scenarios. While larger impacts tolater season water shortages would be expected following the full salvage scenario, there is alot of uncertainty about how large an effect this could be; that is, how many days earliermaximum freshet flows could occur. Because of extensive inter-basin flow routing andreservoir management, for either management scenario this effect is expected to be relativelysmall, and would not significantly affect reservoir storage in the later growing season. Theeffect on freshet advancement and later growing season water supplies from global climatechange is expected to be larger than MPB/salvage impacts.

There are generally moderate fish presence and habitat values along the entire Hydraulic Creekmainstem and high values in the upper watershed lakes and in Reach 3 in the lower mainstem.Because MPB and salvage effects are not expected to significantly change conditions in thelakes or in the mainstem below McCulloch Reservoir risks to fish values are low almosteverywhere in the watershed. Risks to fish values in the lower Hydraulic mainstem areconsidered moderate, because of the slightly higher channel sensitivity to disturbance thanelsewhere in the watershed. However because of the very controlled flows below the reservoir,significant channel and fish habitat impacts are not expected.

Again, because of the low to very low hydrologic hazards throughout the watershed, risks tonon-municipal water supply infrastructure are also low to very low. The few private waterlicenses are located on upper watershed lakes, where little post MPB or salvage impacts areexpected. The KVR / Trans-Canada Trail has generally adequate drainage structures with alow vulnerability to impacts. Forestry road drainage structures are located in the upperwatershed basins and appear adequate for current flows. They have a moderate vulnerability tothe generally low likelihood of significantly increased peak flows, for a low MPB/salvagerelated risk. Private farm bridges are considered highly vulnerable to increased peak flows.However their location below the McCulloch Reservoir, where discharge is highly controlledand increased peak flows are not expected following either management scenario, result in alow MPB/salvage-related risk to these structures.

6.2 RECOMMENDATIONS

Since there are, with one exception, no expected post-MPB and/or salvage harvesting-relatedrisks greater than low, few mitigation measures are required. The moderate risk to fish valuesin the lower hydraulic mainstem means that noticeable post MPB/salvage effects may or mayoccur, and if there are noticeable effects they will be small. Continued normal control offreshet and low flow discharges from McCulloch Reservoir by SEKIDS should adequatelymanage this risk.

The low risks associated with salvage harvesting assume normal good forestry practices toprevent significant hillslope runoff interception and concentration to streams, which couldincrease peak flow and sediment regimes in channels. In particular good riparian managementpractices are recommended. This includes maintaining adequate riparian reserves of stands thatoften have a significant non-pine component. These stands will provide long term temperaturebenefits, bank and floodplain stability and large woody debris recruitment opportunities, if theyare preserved and managed to prevent post- harvest blow-down.


56

The results of data collection and modelling in this investigation suggest that even if all pine-leading stands were harvested, there would generally be low hydrologic risks to all watershedvalues. However ECA analyses are based on average stand conditions derived from limitedfield measurements of secondary stand structure. It is apparent from our results that the localVRI data, particularly in under-estimating the non-pine component of stands identified as pine-leading, is somewhat to quite inaccurate.

From a strictly hydrological perspective (and we recognize forest managers have to balancemany different forest values), the least hydrological impact would result if pine-leading standswith the lowest non-pine overstory component and lowest understory stocking werepreferentially targeted for salvage harvest. The data collected for this investigation suggeststhat, on average, stands with the least hydrological function are younger MSdm stands followedby older MSdm stands and then ESSFdc stands. We recognize that individual stands withinthese broader classifications will have different characteristics, and it is understood that sitespecific evaluations of stand structure should supersede these broader recommendations inmaking harvesting management decisions. To that effect, licensees carrying out salvageharvesting in the watershed should measure and record secondary stand structure during recceand layout. They should then use that site specific stand data in a hydrological risk assessmentmethodology that models the effects of secondary stand structure, to determine the likelyhydrological effects of their actual harvesting and retention plans.

This would ensure watershed hydrologic effects are minimized, and avoid unintended localimpacts should harvesting be concentrated in stands with high hydrologic functions nearpotentially sensitive stream reaches, such as those with high fish values or the steeper lowerwatershed tributaries.

With good hydrological risk assessment of specific harvest and retention plans, and with goodpractices during operations, salvage harvesting with a level of risk acceptable to stakeholdersshould be feasible. Nonetheless, the widespread and severe MPB epidemic in B.C. is clearevidence that forests can be subjected to significant unforeseen disturbances with potentiallysignificant consequences. Forest managers should be aware that MPB infestation may not bethe only significant stressor on Hydraulic Creek forests in the near future. Global warming andglobal warming- related disturbances such as other pathogens attacking other tree types(spruce, fir beetle and others) and significant wildfires, etc., are not improbable in the nearfuture. We think that part of the determination of what is an acceptable level of risk shouldinclude considering the hydrological (and other) effects of these other possible disturbances;and that it would be prudent to apply the precautionary principle and preserve some foresthydrological function in the watershed above the minimum required to manage only for MPBand salvage harvesting related impacts.


57

7.0 CLOSURE

This investigation has been carried out in accordance with generally accepted Geoscience andEngineering practice. Geoscience and Engineering judgement have been applied in developingthe conclusions and recommendations in this report. No other warranty is made, eitherexpressed or implied.

We trust that this report satisfies your present requirements. Should you have any questions orcomments, please contact our office at your convenience.

Prepared by: and

Bill Grainger, P.Geo., EngL. Alan Bates, P.Eng.Senior Geoscientist Consulting EngineerGrainger and Associates Consulting Ltd. Streamworks Unlimited


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Alila, Y., Lou, C. and Maloney, D. 2007. Peak Flow and Water Yield Responses to ClearcutSalvage Logging in Meso-scale Mountain Pine Beetle Infested Watersheds. Unpublishedmanuscript.

Anonymous. 1999. Watershed Assessment Procedure Guidebook, Second edition, Version2.1. Forest Practices Branch, Ministry of Forests, Victoria, BC. Forest Practices Code of BritishColumbia Guidebook.

Associated Engineering Ltd. (Associated) 2007. Water Supply and Treatment Cost/BenefitReview. South East Kelowna Irrigation District.

Aqua Consulting Inc., 2008. 2008 Water Master Plan and Financial Review. District ofSummerland.

Beckers, J., Y. Alila and A. Mtiraoui 2002 On the Validity of the British Columbia ForestPractices Code Guidelines for Stream Culvert Discharge Design. Canadian Journal of ForestResearch 32: 684-692.

Coates, D.K., Glover, T., and B. Henderson, 2009. Abundance of Secondary structure inLodgepole Pine Stands Affected by the Mountain Pine Beetle in the Cariboo-Chilcotin. FinalReport 2008/2009. MPB Project 7.22. Forest Sciences, British Columbia Forest Service.

Coulson, C.H., and Obedkoff, W. 1998. British Columbia Streamflow Inventory, WaterInventory Section, Resources Inventory Branch, BC Ministry of Environment, Lands andParks. Victoria, BC.

Dobson, 2004a. Extent of Snow Cover During the 2004 Spring Freshet for thePeachland CreekWatershed. Fourth Year of Snowline Data. Riverside Forest Products and Gorman Bros.Lumber Ltd.

Dobson, 2004b. Extent of Snow Cover During the 2004 Spring Freshet for the Mission CreekWatershed. Fourth Year of Snowline Data. Riverside Forest Products and Gorman Bros.Lumber Ltd.

Dobson, 2004c. 2004 Snowline Survey in Selected Watersheds of the Central and SouthOkanagan. Extent of Snow Cover During the 2004 Spring Freshet. Weyerhaueser CompanyLtd. Okanagan Falls Division.

Dobson, 2004d. Extent of Snow Cover During the 2004 Spring Freshet for the Trout CreekWatershed. Fourth Year of Snowline Data. Riverside Forest Products and Gorman Bros.Lumber Ltd.

Forest Practices Board (FPB), 2007a. The Effects of Mountain Pine Beetle Attack and SalvageHarvesting on Streamflows. Special Investigation Report 16.


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Forest Practices Board (FPB), 2007b. Tree Species Harvested In Areas Affected By MountainPine Beetles. Special Investigation Report 33.

Green, K. 2005 A Qualitative Hydro-Geomorphic Risk Analysis for British Columbia’sInterior Watersheds: A Discussion Paper. Streamline Watershed Management Bulletin Vol.8/No. 2 Spring 2005.

Hassan, M., D. Hogan, and S. Bird. 2008. Mountain Pine Beetle Impacts on ChannelMorphology and Woody Debris in Forested Landscapes. Mountain Pine Beetle Working Paper2008-07. Mountain Pine Beetle Initiative Project #8.40. Natural Resources Canada, CanadianForest Service. Victoria, BC.

Huggard, 2009. Summary of Results from South Okanagan Stand Surveys for MPB-ECAModeling. GACL. Included as Appendix B of this report.

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Ministry of Environment, 1990. Okanagan Area Hydraulic Creek and its Tributaries. WaterQuality Assessment and Objectives (draft). Prepared by H.J. Singleton, Resource QualitySecton, Water Management Branch. Victoria, BC.

Ministry of Environment, 2008. Water Quality Assessment and Objectives for Mission CreekWatershed (draft – not issued). Environmental Protection Division, Water Stewardship Branch,Ministry of Environment. Victoria, BC.

Ministry of Health Services and Ministry of Water, Land and Air Protection, B.C. (MoH),2005. Comprehensive Drinking Water Source to Tap Assessment Guideline, Draft for PilotAssessments. Introduction and Modules 1 through 8.

Pike, Robin G., and Rob Scherer, 2003. Overview of the potential effects of forestmanagement on low flows in snowmelt dominated hydrologic regimes. BC Journal ofEcosystems and Management. Vol. 3, No. 1.

Redding, T., R. Winkler, P. Teti, D. Spittlehouse, S. Boon, J. Rex, S. Dubé, R.D. Moore, A.Wei, M. Carver, M. Schnorbus, L. Reese-Hansen, and S. Chatwin. 2008a. Mountain pine beetleand watershed hydrology. In Mountain Pine Beetle: From Lessons Learned to Community-based Solutions Conference Proceedings, June 10–11, 2008. BC Journal of Ecosystems andManagement 9(3):33–50.

Redding, T., Rita Winkler, David Spittlehouse, R.D. Moore, Adam Wei and Pat Teti, 2008b.Mountain Pine Beetle and Watershed Hydrology: A Synthesis focused on the Okanagan Basin.Can. Water Res. Ass., One Watershed - One Water conference proceedings. Oct 21 to 23,2008. Kelowna, B.C.


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Schnorbus, M., Alila, Y., Beckers, J., Spittlehouse, D. and Winkler, R. 2004. Peak flow regimechanges following forest harvesting in a snow-dominated basin: An exploratory analysis usingnumerical modeling. Unpublished manuscript.

Schnorbus, M., and Alila, Y. 2004. Forest Harvesting Impacts on the Peak Flow Regime in theColumbia Mountains of South-Eastern British Columbia: An Investigation Using Long-TermNumerical Modeling. Water Resources Research, doi:10.1029/2003WR002918.

Scott, D., and Pike, R. 2003. Wildfires and Watershed Effects in Southern B.C. Interior.Streamline Watershed Management Bulletin. Vol.7, No.3.

Stednick, J. 2007. Preliminary assessment of water quantity and quality changes in beetle-killed catchments in north-central Colorado. In T. Redding (Ed.), Proc. Mountain Pine Beetleand Watershed Hydrology Workshop: Preliminary results from research from BC, Alberta andColorado, July 10, 2007. Kelowna, B.C.

Vyse, A., C. Ferguson, D. Huggard, J. Roach and B. Zimonick. 2007. Regeneration belowlodgepole pine stands attacked or threatened by mountain pine beetle in the Kamloops TimberSupply Area. Thompson Rivers University, Kamloops, BC.

Water Management Consultants (WMC), 2005. Trout Creek Water Supply System Water UsePlan, Technical Background Document on Hydrology, Water Usage and Resvoir Operations.Trout Creek Water Use Plan Consultative Committee.

Water Survey Canada (WSC) 2009. Stream discharge records for Stations 08NM010 and08NM011 for the period of station record overlap from May 1976 to July 1981.

Wei, A., Chen, X., and Scherer, R. 2007. Assessment of the impacts of wildfire and MPBinfestation on in-stream wood recruitment and transportation processes in the B.C. Interior. InT. Redding (Ed.), Proc. Mountain Pine Beetle and Watershed Hydrology Workshop:Preliminary results from research from BC, Alberta and Colorado, July 10, 2007. Kelowna,B.C.

Winkler, R., J. Rex, P. Teti, D. Maloney, and T. Redding. 2008. Mountain pine beetle, forestpractices, and watershed management. B.C. Min. For.Range, Victoria, B.C. Exten. Note 88

Wise, M.P., G.D., Moore, and D.F. VanDine (editors), 2004. Landslide risk case studies inforest development planning and operations. B.C. Min. For. Res. Br., Victoria, B.C. LandManagement Handbook No. 56.

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Figure 1. Hydraulic Creek Watershed and Sub-basins Map

Data Sources and Production Notes Produced for Grainger and Associates

Consulting Ltd.· Produced by

Integrated ProAction Corp.Project Filepath: K:\OK_Comm_WS\Analysis\ CW Presentation Fish Habitat Map.mxdProjection/Datum: BC Albers/NAD 83Date of Production: August 25, 2009Author: Chris Long and Wieslaw Kuzio

All Source information provided through the LRDW Download Service on behalf of the Ministry of Environment, including:Raster basemap, Vegetation Resource Inventory, Cadastre, Community Watershed Boundaries, Points of Diversion, and TRIM

Ñ DoS Water IntakeÊ Reach Break

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Figure 5. Hydraulic Creek Watershed Biogeoclimatic Unit Map



Integrated ProAction Corp.Project Filepath: K:\OK_Comm_WS\Analysis\ CW Presentation Bec Variant Map Final.mxdProjection/Datum: BC Albers/NAD 83Date of Production: August 25, 2009Author: Chris Long and Wieslaw Kuzio


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Figure 17. Hydraulic Creek Fish Consequence Value Map



Integrated ProAction Corp.Project Filepath: K:\OK_Comm_WS\Analysis\ CW Presentation Fsh Habitat Map.mxdProjection/Datum: BC Albers/NAD 83Date of Production: August 25, 2009Author: Chris Long and Wieslaw Kuzio


Ñ DoS Water IntakeÊ Reach Break

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Trout Creek Hydrological Risk Analysis GACL, April 2009

Appendix A:

Risk Analysis Definitions


Appendix A: Risk Analysis Definitions

Risk is defined as the product of hazard and consequence:

Hazard x Consequence = Risk

In this report, hazards are the likelihood of specific hydrological changes in the watershed dueto MPB infestation and salvage harvesting-related modifications in watershed forest cover.

Consequences are the presence of some element of value, such as a “sufficient and reliablesupply of safe and aesthetically acceptable water” at the District of Summerland intake, whichcould be impacted by a specific hydrologic hazard. Where the risk analysis focuses on a hazardwhich will impact a particular element, but does not include details of the vulnerability,robustness or economic value of the element, it is known as a “partial risk analysis” (Wise, etal., 2004).

Where the vulnerability and/or the value of the element are considered, the analysis is referredto in this report as the incremental risk. For instance in this report the vulnerability ofinfrastructure such as bridges, etc., are considered. Incremental means an increase in risks dueto the specific hazard and its ultimate source, which in this case are MPB-related standmortality and associated salvage harvesting.

In all cases the hazards and consequence ratings are qualitative. Hazard ratings are expressed asvery low, low, moderate, high or very high. As shown in Table 1, these can be understood asmeaning the specific hazardous event is rare, unlikely - but possible, possible - may or may notoccur, likely to occur and very likely or almost certain to occur, respectively. Consequenceratings are also expressed as very low to very high (5 classes - Table A1) or as low to high (3classes), if there is not enough known about the element at risk to realistically discern morethan 3 levels of its environmental or social value and/or vulnerability.

Table A1. Risk matrix with 5 hazard and consequence classes.

ConsequenceHazard - Likelihood ofOccurrence

Very Low(insignificant)

Low(minor)

Medium(medium)

High(major)

Very High(catastrophic)

Very High (almost certain) Moderate High High Very High Very High

High (likely) Moderate Moderate High Very High Very High

Moderate (possible) Low Low Moderate High High

Low (unlikely, but possible) Very Low Very Low Low Moderate Moderate

Very Low (rare or unknown) Very Low Very Low Low Low Moderate

Adapted from Wise, et al., 2004.


Table A2. Risk matrix with 5 hazard and 3 consequence classes.

ConsequenceHazard Low Moderate High

Very High High Very High Very HighHigh Moderate High Very High

Moderate Low Moderate High

Low Very Low Low ModerateVery Low Very Low Very Low Low

The description of qualitative risk terms are similar to hazard descriptions; a very low riskmeans any impact or damage to the element at risk is unlikely, a low risk means minor impactor damage could occur but is not considered likely, a moderate risk means some impact ordamage may or may not occur, and if it does impacts are not expected to be large, a high riskmeans that significant impact or damage to the element at risk is considered likely, and a veryhigh risk means very significant impacts or damage are considered very likely.

There are other risk matrices in common use. Table A3 is a 5 x 5matix used by B.C. Ministryor Health and B.C. Ministry of Environment is the Comprehensive Drinking Water Source toTap Assessment Guideline (MoH, 2005). In that matrix risk ratings are weighted towards theconsequence values and the resulting risk ratings are more conservative (higher risk rating)than Tables A1 and A2, which are used in this report.

Table A3. Risk matrix suggested in Comprehensive Drinking Water Source to Tap AssessmentGuideline

ConsequenceHazard - Likelihood ofOccurrence

Insignificant(1) VL

Minor(2) L

Medium(3) M

Major(4) H

Catastro-phic(5) VH

Almost Certain (A) VH M H VH VH VHLikely (B) H M H H VH VHPossible (C) M L M H VH VH

Unlikely (D) L L L M H VHRare (E) VL L L M H H

Adapted from MoH, 2005.

The accompanying report provides a qualitative evaluation of potential hydrologic hazardsassociated with MPB attack and salvage harvesting. Suggestions as to qualitative values thatcould be applied specific consequences are made in this report, so that a risk analysis procedurefor the specific hazards can be presented. However the final determination of consequencevalues, the risk analysis methodology and risk matrix used are the responsibility of watershedstakeholders. Risk assessment, which uses the risk analysis results and includes adetermination of what level of risk is acceptable, and what steps should be taken to mitigate thatrisk, is entirely the responsibility watershed stakeholders.


Appendix B:

Summary of South Okanagan Stand Survey Results.

Prepared by Dave Huggard.

S Okanagan Secondary Structure – Results Summary Dave Huggard, Feb. 2009

1

Summary of Results from South Okanagan Stand Surveys for MPB-ECA Modeling

Data summary by David Huggard (Jan 2009). From field data collection by Stuart Parker(Nov-Dec 2008) for Grainger and Associates Consulting Ltd.

Executive Summary

This field study measured overstory composition and understory density in 30 stands,representing 6 major pine-leading stand types in MSdm and ESSFdc forest, which comprise mostof hydrologically important upper elevations of the south Okanagan watersheds studied. The fieldstudy is one component of projecting effects of mountain pine beetle (MPB) and salvage onhydrological equivalent clearcut area (ECA). At least 8 plots per stand, for a total of 245 plots,were used to measure total and well-spaced densities (stems per hectare, sph) of seedlings,saplings and poles by species, and basal area of overstory by species, following suggestedprovincial methods for surveying “secondary structure”. MPB attack status of overstory pineswas also recorded.

In ESSF, the 7 surveyed stands labelled as pure pine or pine-leading were found to haveonly 30% pine basal area, with spruce and subalpine fir equally common. [This is not due toMPB mortality, because MPB-killed pine were included in these surveys.] Older (>110 yr) pine-leading stands in the MS averaged 65% pine, with a mix of subalpine fir, spruce and Douglas-fir.Mid-seral (<110 yr) pine-leading stands in MS were closer to 90% pine.

Understory densities ranged from high in ESSF to moderately high in older MS tomoderately low in mid-seral MS. Counting only trees >1.3m tall that meet spacing andacceptability criteria for good stocking, and excluding lodgepole pine poles (>7.5cm dbh) becausethese may be killed by MPB, understory densities in ESSF averaged nearly 1000 sph. In MSstands >110yr old, density of these well-spaced understory trees averaged 560 sph, while mid-seral MS stands had 280 sph.

In terms of stocking of individual plots, 60% of ESSF plots had at least 1000 well-spacedsph, somewhat higher than the 40% of plots stocked at this level in Kamloops area ESSFdc(Vyse et al. 2007). In MS >110 yr, 30% of plots had at least 1000 well-spaced sph, while 65%had at least 400 well-spaced sph. Only 11% of mid-seral MS plots were stocked at 1000 well-spaced sph, while 32% were stocked at 400 well-spaced sph. These MS values are alsocomparable to results from Vyse et al. in Kamloops area MS stands (15-39% of plots stocked at1000 sph, 40-70% at 400 sph).

Overall, these surveys suggest that ESSF stands should show little effect of MPB onECA, because of dominant non-pine overstory and high understory stocking. Older pine-leadingMS stands will also receive a substantial contribution to reducing post-MPB ECA from non-pineoverstory and a substantial understory. Mid-seral (<110 yr) MS stands will have only a smallinitial contribution due to limited non-pine overstory and moderately low understory levels,although the existing understory will help speed up post-MPB recovery. As in other areas thathave been surveyed in the Southern Interior, non-pine overstory and existing understory areimportant components of pine-leading stands in the southern Okanagan highlands.

The effects on ECA projections of non-pine overstory and existing understory – along withother stand components – are presented in detail in a separate report. An example of a plotshowing the ECA projections for MPB attacked stands and clearcut salvaged attacked standsused in modeling watershed ECA projections for South Okanagan Community Watershedsfollows this summary._________________________________________________________________________


2

Summary of Results from South Okanagan Stand Surveys for MPB-ECA Modeling

Purposes: This study was undertaken to provide information on:

1. Canopy composition,2. Understory trees,3. Current status of mountain pine beetle (MPB) attack,

in pine-leading stands in the south Okanagan highlands1, as part of a project evaluating theeffects of MPB and salvage options on hydrological equivalent clearcut area (ECA). The projectfocused on 6 combinations of age and reported pine percentages in mature pine-leading standsin ESSFdc1 and 2, and MSdm1 and 2. Canopy composition and existing understory areimportant parameters in projecting MPB effects on ECA and the relative short- and long-termbenefits of salvaging and planting versus leaving affected stands unsalvaged. Information onpercentages of pine and non-pine canopy species is provided by forest cover maps, but can be oflow reliability. Understory surveys in pine-leading stands have been conducted in MS and ESSFin adjacent areas, but in the absence of local surveys, opinions about understory were diverse forthe south Okanagan pine-leading stands. The information on current MPB attack allows ECAprojections to start at current conditions in each watershed.

Methods

Sample designSix stand types compose the majority of the pine-leading stands in the hydrologically

important upper elevations of the south Okanagan watersheds (Table 1).

Table 1. Six stand types sampled in the higher elevations of south Okanagan watersheds.

BEC subzone Pine (VRI %) Age (yr) Percent of total Pl area Polygons Plots

ESSFdc 100 70-130 6.7 4 32<80 >130 4.7 3 24

MSdm 100 70-110 22.9 8 64100 >110 25.2 10 85<90 70-90 2.4 2 16<80 >150 6.0 3 24

68.0 30 245

A total of 30 forest cover polygons to sample were chosen randomly from the set of relativelyaccessible stands of these types, with effort roughly proportional to the area of each type.Polygons were on both sides of Okanagan Lake (ESSFdc1 and MSdm1 on the east side,ESSFdc2 and MSdm2 on the west side).

Field measurementsAt least eight plots spaced 50m apart were surveyed in each polygon for a total of 245

plots. In each plot, seedlings (0.3-1.3m tall), saplings (>1.3m tall to 7.5cm dbh) and poles (7.5-15cm dbh) were measured in 3.99m-radius plots. Total and well-spaced undamaged stems weretallied by species for each layer. With the size of the plot, there is a maximum of 8 well-spacedstems per plot (=1600 stems per hectare). Canopy trees (15 cm dbh) were counted by speciesusing a BAF 2 prism. Status of attack by mountain pine beetles was recorded for canopy pines:none, green attack, red attack or grey attack.

1The study area includes the Mission, Hydraulic, Penticton, Lambley, Trepanier, Peachland and Trout

Creek Community Watersheds.


3

AnalysisResults from the two variants of each subzone were combined, because there were

limited samples in each and no obvious differences in the results.Species composition of the canopy was summarized for each plot, then averaged for each

polygon, and finally the polygons were averaged within a stand type. Percent composition wasbased on basal area (BA), because that was provided by the prism plots. BA is assumed toprovide a reasonable representation of canopy composition, which is directly relevant to ECA.

Density of each species, of all non-pine species, and of all species combined wascalculated for each plot, then averaged for the polygon, separately for seedlings, saplings andpoles, for sapling+poles combined and for all three layers combined. Averages and standarderrors (SE) in a stand type were calculated. For saplings and poles, these values werecalculated separately for all trees, and for well-spaced trees. Additionally, the density of allspecies of saplings plus all species of poles except lodgepole pine were also summarized, for alltrees and just well-spaced trees. This value is probably the most relevant for regeneration afterMPB (which is assumed to kill the pole-size lodgepole pine). This total density was summarizedby stand type, and also by the combination of stand type and watershed (allowing watersheds tobe compared within any stand types that they share).

Following the approach of Coates et al. (2006) and Vyse et al. (2007)2, we alsosummarized the proportion of plots in each stand type that were stocked at minimum levels from200 stems per hectare (sph), 400 sph…through 1600 sph. This was done separately for allunderstory layers combined (seedlings, saplings, poles), saplings+poles combined, and for well-spaced saplings+poles. These values were compared to results from Vyse et al. in ESSF andMS subzones in the Kamloops area, and to stocking results from Nigh et al. (2008)3.

The percentage of canopy lodgepole pine in four MPB attack stages – no attack, green,red and grey attack – was summarized by stand type and also by the combination of stand typeand watershed.

Results

Canopy compositionThe two ESSF stand types, including stands labelled 100% pine, had roughly equal basal

areas of pine, spruce and subalpine fir (Table 2). Even in stands labelled as pure pine, themaximum percentage of pine in the canopy was 63.7%, while one of these stands had no pine.The prevalence of non-pine canopy suggests that MPB will have only small effects on ECA inESSF stands in this area. [Note: Pines killed by MPB were included in these canopy surveys, sothe results are not due to pine being removed by MPB.]

In the MS, stands labelled as 100% pine had 86.3% and 74.0% pine basal area, for mid-seral and mature stands, respectively. The stands >110 years had a larger component of

2Coates, K.D., C. Delong, P. Burton and D. Sachs. 2006. Draft Interim Report. Abundance of Secondary

Structure in Lodgepole Pine Stands Affected by the Mountain Pine Beetle. Bulkley Valley Centre for NaturalResources Research and Management 22 p.Vyse, A., C. Ferguson, D. Huggard, J. Roach and B. Zimonick. 2007. Regeneration below lodgepole pinestands attacked or threatened by mountain pine beetle in the Kamloops Timber Supply Area. ThompsonRivers University, Kamloops, BC. Available from Alan Vyse or Dave Huggard.3

Nigh, G.D., J.A. Antos and R. Parish. 2008. Density and distribution of advance regeneration in mountainpine beetle killed lodgepole pine stands of the Montane Spruce zone of British Columbia. Can. J. For. Res.38:2826-2836. They present total trees for each of their plots, but include trees down to 10cm height.They also provide information on the overall proportions of trees in each height class. An approximate ideaof the stocking of saplings+poles in each plot was obtained by assuming that the overall proportion of trees1-10m tall (24.8% of understory trees) applied to each plot. Results were combined for dry, mesic and wetsites, as these shared a similar range of variation in plot-level stocking.


4

subalpine fir and spruce than the 70-100year stands. Mid-seral stands labelled as having <90%pine averaged 91.1% pine, with Douglas-fir being the other substantial component in the twosampled stands. In contrast, the three mature stands labelled as <80% pine averaged 33.0%pine basal area, with subalpine fir, spruce and Douglas-fir all common. The non-pinecomponents will make at least a moderate contribution to reducing ECA effects of MPB in MS,even in “pure pine” stands.

Table 2. Canopy composition in six pine-leading stand types.

BEC Pine (%) Age (yr) Pl Bl Sx Fd Min Max n

ESSFdc 100 70-130 33.3 35.5 31.2 0.0 0.0 63.7 4ESSFdc <80 >130 26.8 31.2 42.0 0.0 25.0 29.7 3

MSdm 100 70-110 86.3 8.6 3.9 0.2 62.9 100.0 8MSdm 100 >110 74.0 11.0 12.3 2.6 30.6 100.0 10MSdm <90 70-90 91.1 1.8 0.8 6.3 83.7 98.4 2MSdm <80 >150 33.0 36.4 19.0 11.5 24.7 39.2 3

Notes: MSdm 100% 70-110yrs and >110yrs contained 0.9% and 0.2% aspen, respectively

Stand type Canopy composition (%BA) Pl range (%)

Stage of mountain pine beetle attackMPB appears to have begun to attack the surveyed mid-seral ESSF stands only recently,

with 89.8% of mature pines not attacked, and more green attack than red or grey (Table 3).Attack rates are also still low in the older ESSF stand type, with 73.3% of pines not attacked. Inolder ESSF, though, the attack began a few years ago, with equal amounts of grey and redattacked trees.

Attack rates are somewhat higher in most MS stands, with a mix of older versus morerecent attack stages in the different types. The old, mixed species stands, despite not having ahigh percentage of pine, had high rates of attack, with only 15.5% of pines not attacked.

Table 3. Percentage of canopy lodgepole pine (Pl) in different stages of mountain pine beetle attack,by stand type.

BEC Pine (%) Age (yr) None Green Red Grey

ESSFdc 100 70-130 89.8 5.0 1.4 3.8ESSFdc <80 >130 73.3 1.8 12.3 12.7

MSdm 100 70-110 68.5 13.7 10.6 7.1MSdm 100 >110 64.0 9.1 16.2 10.7MSdm <90 70-90 73.6 0.9 15.1 10.4MSdm <80 >150 15.5 19.2 39.4 25.9

Stand type Pl Attack status (%)

Much of the variation in attack rates in MS stand types seems to be due to differentamounts of MPB in different watersheds (and the fact that stand types are not equally spreadacross the watersheds.) The Bear Lambly watershed had very few pines that were not attacked,even in ESSF where MPB activity was otherwise low (Table 4). Except in the ESSF, theTrepanier watershed also had high attack rates, but with a higher percentage of recent greenattacked pines than Bear Lambly. The Peachland watershed had moderate attack rates, whileattack rates are still low in the Hydraulic, Mission and Trout watersheds. Although, these resultsare based on only 1 or 2 stands in each stand type in each watershed, they agree with MPBsurvey results for the watersheds provided by Ministry of Forests and Range.


5

Table 4. Percentage of canopy lodgepole pine (Pl) in different stages of mountain pine beetle attack,by stand type and watershed.

BEC Pine (%) Age (yr) Watershed None Green Red Grey

ESSFdc 100 70-130 Penticton 84.6 7.5 2.1 5.8Trepanier 100.0 0.0 0.0 0.0

ESSFdc <80 >130 Bear Lambly 31.6 5.3 36.8 26.3Mission 100.0 0.0 0.0 0.0Penticton 88.2 0.0 0.0 11.8

MSdm 100 70-110 Hydraulic 70.0 14.3 7.9 7.8Trepanier 43.8 25.2 17.3 13.7Trout 92.2 2.0 5.8 0.0

MSdm 100 >110 Bear Lambly 5.6 0.0 61.1 33.3Hydraulic 95.7 0.0 2.2 2.2Mission 71.4 22.2 3.2 3.2Peachland 47.6 14.2 19.9 18.3Trepanier 0.0 34.5 41.4 24.1Trout 92.1 2.1 4.0 1.9

MSdm <90 70-90 Peachland 100.0 0.0 0.0 0.0Trepanier 47.2 1.9 30.2 20.8

MSdm <80 >150 Bear Lambly 13.2 10.5 39.5 36.8Peachland 33.3 25.0 41.7 0.0Trepanier 0.0 22.2 37.0 40.7

Stand type Pl Attack status (%)

Densities of understory treesSaplings were roughly 3 times as abundant as pole-sized understory trees overall, except

in mid-seral MS stands where saplings were rarer (Table 5). Saplings tend to be clustered morethan poles, so that well-spaced saplings and poles are about equally common.

Non-pine understory trees were most common in ESSF, with about 2500 stems perhectare, of which almost 1000 sph are well-spaced (Table 5). Subalpine fir is dominant. Theunderstory in these stands is close to “well-stocked”. There are few understory pines in thesestands.

Well-spaced non-pine understory is fairly sparse in mid-seral MS stands, with 213 or 281well-spaced sph in the two mid-seral stand types (Table 5). There is, however substantial pineunderstory in these types, raising the density of well-spaced understory trees to 413 or 688 sph.Well-spaced understory trees are denser in older MS, dominated by subalpine fir. Well-spacedtotals for all species are 600 and 726 sph in the two types of older MS. All these values onlyinclude trees >1.3m height.

Table 5. Densities of poles, saplings and poles+saplings combined (with SE), total and well-spaced (WS), by species and stand type.

BEC Pine (%) Age (yr) Layer

ESSFdc 100 70-130 poles 13 (13) 6 (6) 544 (112) 319 (28) 106 (41) 44 (12) 650 (126) 363 (30) 663 (139) 369 (26)

saplings 0 0 1663 (444) 513 (82) 131 (62) 75 (42) 1794 (484) 588 (118) 1794 (484) 588 (118)

combined 13 (13) 6 (6) 2206 (384) 831 (90) 238 (51) 119 (37) 2444 (407) 950 (117) 2456 (401) 956 (113)

ESSFdc <80 >130 poles 50 (29) 17 (17) 442 (51) 308 (58) 108 (85) 100 (76) 550 (52) 408 (22) 600 (80) 425 (38)

saplings 0 0 1833 (639) 508 (60) 208 (123) 67 (55) 2067 (517) 583 (68) 2067 (517) 583 (68)

combined 50 (29) 17 (17) 2275 (652) 817 (106) 317 (205) 167 (131) 2617 (467) 992 (88) 2667 (443) 1008 (101)

MSdm 100 70-110 poles 647 (285) 397 (152) 75 (26) 59 (23) 69 (42) 56 (32) 153 (67) 119 (55) 800 (275) 516 (147)

saplings 206 (120) 9 (7) 225 (130) 109 (52) 131 (58) 53 (23) 356 (162) 163 (64) 563 (170) 172 (62)

combined 853 (403) 406 (155) 300 (153) 169 (72) 200 (75) 109 (39) 509 (222) 281 (110) 1363 (408) 688 (161)

MSdm 100 >110 poles 276 (129) 177 (95) 148 (67) 120 (54) 41 (14) 35 (14) 189 (69) 155 (56) 465 (127) 332 (92)

saplings 25 (11) 5 (5) 934 (252) 366 (85) 36 (13) 23 (7) 970 (257) 390 (85) 995 (255) 395 (84)

combined 301 (130) 182 (95) 1081 (288) 487 (124) 77 (23) 58 (18) 1159 (299) 545 (127) 1459 (259) 726 (114)

MSdm <90 70-90 poles 325 (250) 188 (138) 150 (150) 117 (117) 13 (13) 13 (13) 225 (100) 150 (25) 550 (350) 338 (163)

saplings 25 (25) 13 (13) 525 (475) 50 (25) 88 (88) 13 (13) 613 (563) 63 (38) 638 (588) 75 (50)

combined 350 (275) 200 (150) 675 (625) 138 (113) 100 (75) 25 838 (663) 213 (63) 1188 (938) 413 (213)

MSdm <80 >150 poles 8 (8) 0 225 (66) 175 (66) 50 (29) 50 (29) 275 (88) 225 (88) 283 (92) 225 (88)

saplings 0 0 1458 (512) 358 (179) 92 (92) 17 (17) 1550 (603) 375 (189) 1550 (603) 375 (189)

combined 8 (8) 0 1683 (567) 533 (243) 142 (96) 67 (33) 1825 (663) 600 (277) 1833 (660) 600 (277)

Notes: MSdm <90% pine, 70-90yrs also included 63 Fd poles/ha, with 50/ha well-spaced

A few cedars and aspens (not shown) occurred in the understory at a few sites.

WS = well-spaced

Total WSAll non-pine (/ha) All species (/ha)

Total WS Total WS Total WS Total WSStand type Lodgepole pine (/ha) Subalpine fir (/ha) Spruce (/ha)

A heavy MPB infestation can kill pole-sized lodgepole pine. The best summaryof surviving understory densities expected after severe MPB is therefore sapling andpoles of non-pine species, plus saplings only of lodgepole pine. Densities of this groupare around 2500 sph in ESSF, 1800 sph in old MS, declining to about 800 in mid-seralMS (Table 6). ESSF has nearly 1000 well-spaced sph of this group, older MS has about600 sph and mid-seral MS has 250 sph. These levels could be described as “almoststocked”, “half stocked” and “mostly unstocked”, respectively.

Table 6. Total and well-spaced (WS) densities of saplings+poles combined, but excludinglodgepole pine poles (with SE).

Poles+Saplings total density (no Pl poles)

BEC Pine (%) Age (yr)

ESSFdc 100 70-130 2444 (407) 950 (117)

ESSFdc <80 >130 2617 (467) 992 (88)

MSdm 100 70-110 716 (215) 291 (107)

MSdm 100 >110 1184 (298) 550 (126)

MSdm <90 70-90 863 (688) 225 (75)

MSdm <80 >150 1825 (663) 600 (277)

Note: WS = well-spaced

Stand type Pole+Sapling density (/ha; no Pl poles)Total WS

Plot-level stocking distributionThe above values are stand-level averages. It is also important to look at what

proportions of individual plots are stocked to different stocking levels. The summariesinclude results for all understory layers (seedlings+saplings+poles), for justsaplings+poles, and for well-spaced saplings+poles.

With all understory trees, or all saplings+poles, the majority of ESSF stands arestocked to the highest levels examined (1600 sph; Table 7). Over half of the plots inESSF stand types are stocked to 1000 sph with well-spaced trees4. The stocking levelsare moderately higher than levels reported by Vyse et al. for ESSFdc3 stands in theKamloops area. [Note: Vyse et al. reported on “acceptable trees”, based on height, stemform and lack of disease, but no spacing criterion, so these results are not completelycomparable to the well-spaced densities reported here.]

Table 7. Percentage of individual plots in ESSF that are stocked to different levels (stemsper hectare, SPH), for all understory layers (seedling+sapling+poles),saplings+poles only, and well-spaced saplings+poles, with comparison to resultsfrom Vyse et al.

ESSFStudy BEC Pine (%) Age (yr) Plots Layers 200 400 600 800 1000 1200 1400 1600

This study ESSFdc 100 70-130 32 All 97 97 94 91 91 91 91 91Saplings+Poles 97 97 91 84 81 78 66 66

Saplings+Poles well-spaced 97 97 88 66 56 34 28 9

This study ESSFdc <80 >130 24 All 100 100 100 100 100 100 100 100

Saplings+Poles 100 96 96 96 92 92 92 88Saplings+Poles well-spaced 96 92 83 79 63 46 25 13

Vyse et al ESSFdc3 Pl leading >60 All 100 100 100 100 100 100 100 100Saplings+Poles 100 92 72 64 56 48 36 36

Saplings+Poles acceptable 84 64 56 48 40 36 20 20

Percent of plots with understory density >= specified SPH

4Given the plot size and the minimum spacing for a well-stocked tree, the maximum physically

possible value for well-spaced stocking is 1600 sph.


8

In mid-seral MS stands, half the plots are stocked at 800 sph with all understorylayers, but more than half the plots have <400 sph of well-spaced saplings+poles (Table8). Older MS stands have more than half their plots stocked to 1600 sph with all layers,but half the plots have less than 600-800 sph of just well-spaced saplings+poles. 29%of plots in these older MS stands had <200 well-spaced sph. Vyse et al. found similarplot-level stocking distributions for the drier MSxk2, and moderately higher stocking inMSdm3 plots. Nigh et al. reported generally lower understory stocking in mature MSstands in the Merritt area5.

Table 8. Percentage of individual plots in MS that are stocked to different levels (stems perhectare, SPH), for all understory layers (seedling+sapling+poles), saplings+polesonly, and well-spaced saplings+poles, with comparison to results from Vyse et al.and Nigh et al.

MSStudy BEC Pine (%) Age (yr) Plots Layers 200 400 600 800 1000 1200 1400 1600

This study MSdm 100 70-110 64 All 73 66 53 50 47 38 33 25Saplings+Poles 69 58 44 36 30 22 19 16Saplings+Poles well-spaced 48 31 20 16 14 13 3 0

This study MSdm 100 >110 85 All 86 75 69 64 61 58 55 53Saplings+Poles 76 67 58 48 46 44 39 32Saplings+Poles well-spaced 71 64 45 41 32 19 6 5

This study MSdm <90 70-90 16 All 81 69 56 50 44 31 31 25Saplings+Poles 81 63 44 38 31 31 19 19Saplings+Poles well-spaced 75 38 0 0 0 0 0 0

This study MSdm <80 >150 24 All 100 92 88 83 83 79 75 67Saplings+Poles 96 88 75 75 71 58 50 42Saplings+Poles well-spaced 71 67 54 46 25 17 13 8

Vyse et al MSdm3 Pl leading >60 All 97 96 96 95 92 92 92 89Saplings+Poles 91 82 69 58 55 51 49 43Saplings+Poles acceptable 88 70 57 45 39 27 26 22

Vyse et al MSxk2 Pl leading >60 All 94 83 75 64 56 51 46 42Saplings+Poles 81 62 48 40 31 23 18 14Saplings+Poles acceptable 60 40 29 24 15 11 7 5

Nigh et al MS >70 Mature 28 Saplings+Poles (approx) 61 39 25 14 7 7 7 7

Percent of plots with understory density >= specified SPH

5The Nigh et al. values are approximate calculated values that may not be equivalent to the

survey results from this study or Vyse et al.


Appendix C:

Channel Sensitivity Method and Results

Hydraulic Creek Hydrological Risk Analysis GACL, August 2009

Appendix C: Channel Sensitivity Method and Results

Table C-1 (adapted from Green, 2005) is a framework for assigning channel sensitivityratings based on characteristics from field, airphoto and map observations.

AlterationChannel Sensitivity

Rating(H, M, L)

Channel Attributes that May Contribute to Channel Sensitivity

Low Channel experiences frequent natural, large peak flow events (e.g. steep watershed, rapidrunoff, high snow pack).

Channel has endured high flow events in the past with little evidence of long term change. Channel exhibits a natural resiliency to bank and bed scour/erosion (e.g. bedrock controls,

extensive colluvial or lag deposits, well-vegetated, deep-rooted riparian vegetation). Abundant instream LWD, debris jams and lag boulders that augments channel and bank

stability through energy dissipation. Frequent sizeable lakes, wetland areas and/or broad floodplain able to store significant

water volume and attenuate flood peaks.

Moderate Range or combination of attributes listed above and below.

IncreasedPeak

Dischargeand/orFlood

Frequency

High Channel does not experience frequent flood events (dark mossy substrates, maturevegetation to high water mark).

Relatively recent flood events (past 20 years) have caused significant disruption of channeland/or bank stability.

Channel segments with fine textured banks and substrates that are susceptible toscour/erosion.

Lacking in channel structure (e.g. instream LWD, lag boulders, bedrock) that wouldabsorb flow energy.

Little or no lakes, overflow channels, floodplain or low gradient wetland segments thatwould attenuate/store flood peaks.

Low Channel experiences frequent high volumes of sediment delivery from upstream/upslopesources (e.g. numerous natural landslides, ravelling banks, naturally aggraded channel).

Evidence of older, connected landslides and/or debris flows with minimal evidence of longterm changes to channel stability.

Abundant locations for sediment storage, such as frequent functioning debris jams or lowgradient, unconfined sections that arrest bedload movement.

Slow-flowing, meandering stream with insufficient power to transport bedload and allowsome settling/filtering (e.g. frequent wetland segments).

Stable/resilient banks that will resist widening following sediment storage/aggradation. Coarse sediment is easily passed through the channel system with minimal accumulations

(in context of watershed, may lead to issues downstream – see notes).


IncreasedSedimentDelivery

[Finesuspendedand Coarse

bedloadsedimentshould beconsideredseparately]

High Channel does not experience frequent high volumes of sediment delivery fromupstream/upslope sources (e.g. dark mossy substrates, deep pools, broadly gradedsubstrates).

Evidence of channel destabilization in response to isolated sediment events (e.g. older,connected landslides have caused aggradation/channel widening downstream).

Channel has little or no sediment storage capacity such that increases in sediment deliveryare likely to cause channel aggradation, lateral erosion and/or avulsion.

Fine sediment is rapidly passed through with little opportunity for settling/filtering(reducing water quality downstream).

Channel has frequent erodible banks that will allow channel widening in response toaggradation and contribute further sediment to the channel.

Low Channel flows through area of naturally low-growing riparian vegetation (e.g. wetland,alpine area or avalanche pathway).

Channel is not dependant on LWD to provide channel or bank stability (e.g. bedrockcontrolled, colluvial and/or lag deposits, steeper Step-Pool or Cascade-Pool morphologytypes).

Channel has experienced localized decreased riparian condition in the past (e.g. wildfire,harvesting) with little indication of long term instability.

Channel is not dependant on LWD to control bedload movement. Channel is not dependant on riparian vegetation to maintain fish habitat values, including

instream LWD, food sources and/or stream temperature moderation.


DecreasedRiparianFunction

High Channel is dependant on LWD to provide channel or bank stability (e.g. erodible banks,Riffle-Pool morphology type).

Channel has experienced localized decreased riparian condition in the past (e.g. wildfire,harvesting) resulting in local destabilization.

Channel is dependant on LWD to control bedload movement. Channel is dependant on riparian vegetation to maintain fish habitat values, including

instream LWD, food sources and/or stream temperature moderation.


Appendix D:

Hydraulic Creek Fish Values by Reach

Prepared by Michele Trumbley, R.P. Bio.

Trumbley Environmental Consulting Limited

1 of 7 4574 Larkin X Road, Armstrong, B.C. V0E 1B6 • Tel: 250-546-4069 • Fax: 250-546-8796

[email protected] • www.trumbleyenvironmental.ca

Attn: Bill Grainger, P.Geo. Grainger & Associates Consulting Ltd. March 31, 2009 Box 427 Salmon Arm, B.C. V1E 4N6 RE: Fisheries Information on the Hydraulic Creek Watershed as one of Seven Identified Okanagan Community Watersheds HYDRAULIC CREEK Hydraulic Creek (WSC1 310-794400-22400) is a tributary of Mission Creek and is a sub-basin of the Mission Creek Watershed which flows into the eastern shore of Okanagan Lake in Kelowna. The watershed has been delineated into 3 sub-basins including Hydraulic and McCullough Residuals and the Fish Lake sub-basin. The fish and fish habitat investigation is one component of several factors used to develop an overall risk rating for MPB2. FISH SPECIES Sportfish species within the watershed include Brook Trout (Salvelinus fontinalis) and Rainbow trout (Oncorhynchus mykiss). Kokanee (Oncorhynchus nerka) spawn in Mission Creek however are not documented within Hydraulic Creek. Numerous lakes are stocked within the Hydraulic Creek sub-basin therefore fish presence was largely confirmed through stocking records. OBSTRUCTIONS Obstructions to upstream fish migration include a series of dams at the outflows of Browne Lake, Long Meadow Lake, Haynes Lake and McCulloch Reservoir (Hydraulic Lake). The dams are an obstruction to the movement of fish upstream however fish have been documented upstream of the barriers. In addition, all lakes are known to contain fish with the exception of Long Meadow Lake and Weddle Lake, therefore fish presence is likely throughout the watershed despite barriers to upstream fish migration. RISK ASSESSMENT A consequence table was developed to identify reaches of special concern because the likely effect of MPB on fish and fish habitat within the Hydraulic Creek watershed is largely unknown. The sub-basins were delineated into macro-reaches which were used to target sensitive areas (Table 2). Therefore mitigation strategies can be developed in target areas where negative impacts are probable. Habitat quality data in addition to historical site visits were sparse therefore interpretations of potential habitat quality were at the discretion of the professional biologist. In areas were habitat quality was unknown, an

1 WSC –Watershed Code 2 MPB – Mountain Pine Beetle




estimated channel width in combination with gradient and connectivity was utilized to predict the consequence rating. Table 1 outlines the criteria utilized in determining the consequences for fish and fish habitat. Priority 1 2 3 4

Consequence Rating

Fish Species Present Habitat Quality Channel

Gradient %

Average Channel

Width (m)

VL fish absence

fish absence confirmed, minimal fish habitat

available, habitat degradation low risk to fish

>20% <1.5

L presence of RB

Fish Absence Confirmed and/or habitat with low

rearing potential for the fish species present

16% - 19% 0-5

M presence of RB, EB habitat quality low to moderate 9% to 15% 0-5

H presence of RB, EB, MW

fish presence confirmed, habitat quality moderate to

high 0% to 8% 0-20

VH presence of RB, EB, KO, MW

fish presence confirmed, habitat quality high 0% to 8% 0-20

Note: VL – Very Low L – Low M – Moderate H – High VH – Very High




Table 2- Hydraulic Creek Watershed Consequence Rating Stream Name

WSC Reach Average Channel Width (m)

Gradient (%)

Species Present

Habitat Quality

Consequence Rating

Hydraulic Creek

310-794400-22400

1 5-20 7 RB Low gradient M – moderate habitat quality, low gradient

Hydraulic Creek

310-794400-22400

2 5-20 7 RB Low gradient M – moderate habitat quality, low gradient

Hydraulic Creek

310-794400-22400

3 12 3 RB Excellent fish habitat however excessive LWD, windfall issues on both banks

H – excellent habitat, RB present , however excessive LWD

Hydraulic Creek

310-794400-22400

4 5-20 3 RB Dams located in reach 4

M – moderate quality habitat, low gradient

Hydraulic Creek

310-794400-22400

5 5-20 1 (RB) Low gradient L – low gradient, possibility connectivity to fish

McCulloch Reservoir (Hydraulic Lake)

01063OKAN 6 N/A N/A EB and RB (hatchery and resident)

Four dams on lake, Stocked with RB 1967 to 2008

H – dam will prevent upstream migration however RB and EB present in tributaries upstream

Hydraulic Creek

310-794400-22400

7 0-5 1 EB and RB Inflow to Hydraulic Lake, likely rearing habitat

M – low gradient, overwintering potential in Hydraulic Lake

Duck Lake 310-794400-22400

8 N/A N/A No species documented (EB, RB)

Not stocked M – connectivity to fish, low gradient

Hydraulic Creek

310-794400-22400

9 0-5 3 (RB EB) Connection to EB in Turtle Lake

M – low gradient, connection to EB

Unnamed tributary

N/A (station 1 on map)

1 1.62 35 NFC (S6) Gradient barrier, substrate boulder and bedrock

VL – excessive gradient, low quality habitat

Myra Creek 310-794400-22400-15800

1 0-5 25% (non-fish) Gradient barrier

VL – excessive gradient, low quality habitat






Gradient (%)

Species Present

Habitat Quality

Consequence Rating

Knox Creek

310-794400-22400-44900

1 0-5 1 No species documented (RB)

No data available

M – low gradient, connection to Hydraulic Creek

Knox Lake

01055OKAN 2 N/A N/A No species documented (RB)

Not stocked L – suspected RB, possible overwintering potential

Weddle Lake

01048OKAN 3 N/A N/A No species documented (RB)

None documented, Not stocked

L – suspected RB, possible overwintering potential

Fish Lake

01008OKAN; 310-794400-22400-44900-3240

2 N/A N/A RB and EB (hatchery and resident

None documented, Stock with EB to 1976 2008; RB 1962 to 1966

M – RB & EB confirmed, overwintering potential

Browne Lake

00990OKAN; 310-794400-22400-44900-3240

4 N/A N/A RB (hatchery and resident

Dam at outflow, Stocked with RB from 1937-2008

M – RB confirmed, overwintering potential

Long Meadow Lake

01003OKAN 1 N/A N/A (RB) Dam at outflow, Not stocked

L – dam at outflow will prevent overwintering and rearing in lake

Ern Lake 01067OKAN 1 N/A N/A EB Stocked, no habitat data available

H – connection to upstream tributaries and overwintering potential in Hydraulic Lake

Minnow Lake

01096OKAN 1 N/A N/A RB (hatchery and resident)

Stock with RB 1968 to 2008

H – stocked with RB, connectivity to Haynes and Hydraulic Lakes

Pear Lake

01100OKAN 1 N/A N/A RB (hatchery and resident,

Stocked with RB 1968 to 2008

M – dam out inflow of Haynes is obstruction to overwintering habitat, connection to tributary

Haynes Lake

01106OKAN; 310-794400-22400-51300

1 N/A N/A RB (hatchery and resident,

Dam at inflow, Stocked with RB 1967 to 2008

H – connection to Minnow Lake, stocked with RB






Gradient (%)

Species Present

Habitat Quality

Consequence Rating

Turtle Lake

01109OKAN N/A N/A EB, all hatchery fish,) (RB)

Stock with EB 1977 to 2008;

M – connection to Stirling Creek, stocked with EB

Acme Lake

00376KETL N/A N/A (RB, EB) Not stocked L – small lake, limited overwintering potential

Stirling Creek

320-520100-42900-40600

2 0-5 4 RB (resident fish,

No habitat data available

M – RB confirmed, connection to Canyon Lakes and Hydraulic Creek

Canyon Lakes

00479KETL 3 & 5 N/A N/A RB (resident fish,

Not stocked H – resident RB, connection to Stirling Creek downstream

Fish Species Codes: RB – Rainbow Trout EB- Brook Trout (species) – suspected fish presence NFC – No fish caught NS – Not Sampled MITIGATION STRATEGIES Mitigations to maintain fish presence is often difficult to determine. The impacts of MPB will ultimately reduce riparian cover. The dynamics of stream ecosystems are dependent on the presence of intact multi stage riparian zones. The LWD3 and CWD4 supplies organics to the channel thereby enabling the growth of invertebrates used as food for fish. Insect drop from adjacent riparian vegetation also provides a valuable food source for fish. In addition, riparian vegetation provides important value in maintaining stream temperatures and limiting bank failure and sloughing. The influx of sediment into a channel increases turbidity which aside from having detrimental effects by clogging fish gills, it also inhibits feeding which is sight dependent. Therefore, an important mitigation strategy is to encourage the growth of riparian vegetation in areas where very high and high value consequences were identified. Planting of a mixed stand will provide habitat in areas where MPB has removed the adjacent riparian vegetation. In addition, point sources of sediment should be targeted and rectified. Water flows should be monitored to ensure minimal flows during critical periods which include summer months where fish may be stranded.

3 LWD – large woody debris 4 CWD – coarse woody debris




SUMMARY OF RISKS TO FISH HABITAT: This summary is to be used in conjunction with the Channel Evaluation Table and is summarized according to sub-basin. Hydraulic Residual: The Hydraulic Residual includes reaches 1-5 of Hydraulic Creek and all tributaries downstream of Hydraulic Lake. Reach 3 of Hydraulic Creek was assigned a high consequence rating based on the high quality habitat in combination with excessive LWD and windfall issues on both banks. Reach 3 is likely more susceptible to peak flows. The remainder of the residual area was assigned a moderate consequence rating based on habitat quality. McCullough Residual: The McCullough Residual includes Hydraulic Lake and all the tributaries and lakes upstream. A consequence rating of high was assigned to Hydraulic Lake and the remainder of the ratings ranged from moderate to high based on habitat quality. Brook trout and Rainbow trout are documented within the residual and brook trout have an increased sensitivity to peak flows and sedimentation. Fish Lake Sub-Basin: Rainbow trout and Brook trout are documented in Fish Lake. Fish and Browne lakes provide overwintering and rearing potential and consequence ratings were moderate. The Fish Lake Sub-bains includes Fish, Browne and Long Meadow Lakes.




REFERENCE MATERIAL Reference material was obtained by the following:

• Summit Environmental Consultants Ltd., 1996, Mission Creek Watershed Stream Assessment, MELP.

• FISS 8002, Lake Plans – Okanagan Watershed. MELP, Jan 01, 1995 for Browne Lake, Fish Lake, Haynes Lake; Lake Plans – Okanagan Watershed, MELP

• FISS 8187, Jan 01, 1995 • FISS 8194, Jan 01, 1995 • FISS 8212, Hydraulic Creek; Report – A general fish inventory of streams in the South

Okanagan and Similkameen watersheds, MELP, 1994, • FISS 8354, Minnow Lake. File # 34020-20-02, MELP, Jan 01, 1995 • FISS 8358, Haynes Lake. File #: 34020-20-02, MELP, Jan 01, 1995 • FISS 8360, Hydraulic Lake. File #: 34020-20-02, MELP, Jan 01,1995 • FISS 8361, Fish Lake, File # 34020-20-02, MELP, Jan 01, 1995 • FISS 8362, Ern Lake, File # 34020-20-02, MELP, Jan 01, 1995 • FISS 8363, Browne Lake. File #: 34020-20-02, MELP, Jan 01, 1995

Should you have any questions regarding the content of this report, please contact the undersigned at your convenience. Thank-you Michele Trumbley, R.P.Bio Trumbley Environmental Consulting Limited


Appendix E:

Okanagan Flood Frequency Shift Analysis


Appendix E: Okanagan Flood Frequency Shift Analysis

An assessment of flood frequency and magnitude can be used to compare watershedcharacteristics temporally and spatially. Flood frequency curves may change with time due tochanges in climate, land use (e.g., drainage improvement) and forest cover. Flood frequencycurves can be used to compare adjacent watershed characteristics (i.e., flashiness (routingefficiency) runoff quantities and rates, storage, etc.). Watershed characteristics are reflectedin the relative slope and position of the frequency curve.

Spring peak flow generation in nival watersheds is a complex process involving snow pack,forest cover, microclimatology and weather. Extensive literature reviews of research findingson the relationship between harvesting and peak flows, largely through paired-watershedstudies, have concluded that there is wide variability between results. There is no singlevariable – such as the amount of forest cover removed, harvesting system, etc. that allows fora quantitative description of changes in peak flows associated with timber harvesting (Schererand Pike, 2003). This is because of the wide range of forest management histories, weatherconditions and events, physical properties, forest cover types, watershed drainagecharacteristics, etc., as well as different analytical and statistical methods used in the manystudies.

This study uses the results of several recent numerical modeling-based analyses of therelationship between forest canopy changes due to harvesting, MPB infestation, or both, andrunoff regime. Numerical modeling removes some of the uncontrolled variables inherent inpaired-watershed studies, such as weather history, and allows testing of various treatmenthypotheses. In all cases, watershed models were calibrated using some period of existingclimate and runoff data. Nonetheless, modeling watershed processes requires making manyassumptions, which introduce uncertainties, especially when extrapolating from experimentalwatersheds to operational situations in different watersheds.

The modelling results for 11 nival Interior B.C. modelled watersheds are presented below.Nine are in the south Okanagan (Whiteman (112km2), Vaseaux above Dutton (255km2),Bellevue (73km2), Camp (34km2), Dave (31km2), Vaseaux above Solco (112km2), Pearson(74km2), Ewer (53km2) and 240(5 km2) Creeks and two are in the upper Fraser River basin(Naver Ck.(658 km2) and Baker Ck. (1570 km2). They have different sizes, geographiclocations, physical and climatic characteristics and treatments. Baker Ck. and 240 Ck. weremodelled with the Distributed Hydrology Soil Vegetation Model (DHSVM) and the rest withthe UBC Watershed Model (UBCWM).

Figures C-1 to C-3 show some of the watersheds modelled and the expected flood frequencyshifts with the various treatment levels, which range from 50% clearcut or ECA, to 100%clearcut and ECA. 240 Creek is about 1/100 the size of Trout Creek and Baker Creek abouttwice as large.

Results from Naver Creek and the other mid-sized Okanagan watersheds modelled(Whiteman, Vaseaux 1 and 2, Bellevue, Dave, Pearson and Ewer) modelled as 100% clearcutwith UBCWM show similar flood frequency shifts as Camp Creek.


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Figure C-1. Modelled flood frequency shift for 240 Ck., a 5km2 tributary of Penticton Creek, with 40%and 50% clearcutting of upper watershed harvested. With 50% clearcutting the 50 year flood

would be expected to occur on average every 5 years. Data from Schnorbus et al. 2004.

Figure C-2: Modelled flood frequency shift for Baker Creek (1570km2) with approximately 60% ECA,from clearcutting an MPB pine mortality. The 50 year flood becomes about the 11 year flood.


Pearson Creek Flood Frequency

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To extrapolate to the expected flood frequency shift to a lower ECA value all the modelledresults would have to be scaled down, i.e., the amount of flood frequency shift reduced.

We also note the slight divergence between the control and treatment flood regimes, such thatlarger (longer return period) floods show somewhat larger increases in magnitude thansmaller floods. We have extrapolated these results to lower ECA values by maintaining thatdivergence and scaling the overall size of flood frequency shift down from any of themodelled watersheds, as shown in Figure C-3. With a sustained high ECA, the 50 year returnperiod flood would be expected to occur on average every 20 years.

Figure C-3. Modelled flood frequency shift for Pearson Creek, a 74km2 tributary of Mission Creek; with 100% offorested watershed area clearcut harvested. The historic 50 year flood would be expected to occur every 7 years

Pearson Creek1961 to 1993

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High (35 to 50% ECA

hydraulic creek hydrological risk assessmenta100.gov.bc.ca/appsdata/acat/documents/r17101/... ·...

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