Agua Hedionda Watershed Management Plan Watershed Planning Group MeetingMarch 27, 2008Carlsbad, CA

Agenda Preliminary Modeling Results

LID Constraints and Conceptual Designs

Evaluation Process for Identifying Acquisition, Restoration, and BMP Retrofit Opportunities

Finalizing Goals and Objectives

Preliminary Modeling Results

Modeling ObjectivesRepresent watershed hydrology and pollutant loadingAssess hydromodification and water qualitySimulate various development scenarios

Model ScenariosExisting Condition (based on 2007 SANDAG land use)Predevelopment Condition (all development converted to open space)Future Condition (based on 2030 SANDAG land use)Representation of lawn irrigation and BMP treatment has been incorporated

LSPC ModelLSPC is the Loading Simulation Program in C++, developed by the U.S. Environmental Protection Agency (EPA) Region 4, with support of TtWatershed modeling system includes streamlined HSPF algorithms for simulating hydrology, sediment, and general water quality on land and in streamUsed to represent the build up, wash off, and first order decay processes of pollutants and sediment processes (on land and in channel)

HydrologyHydrologic Components:

PrecipitationInterceptionEvapotranspirationOverland flowInfiltrationInterflow Subsurface storageGroundwater flowGroundwater lossSchematic of Stanford Watershed Model

Model InputsLand use data from SANDAG; modified using parcel data for finer resolution of residential categories; future land use modified based on feedback from municipalitiesPrecipitation from Oceanside Pumping Plant; PET from a variety of CIMIS stationsModel subwatersheds delineated from 10m DEM; stream characteristics based on drainage area:width/depth relationshipsDemand-based lawn irrigation

Model ParametersInitial basis for parameterization:Hydrology: San Diego Region TMDL Model and other SoCal model applicationsBacteria: San Diego Region TMDL Model (Bacti-II Draft) Nutrients: San Jacinto modelSediment: SCCWRP regional sediment approachLocal watershed propertiesSome parameters adjusted during calibration

Model CalibrationBegan with regionally calibrated model (to flow and bacteria)Some additional but limited local calibration was possible~1 year of stream flow data (2005-2006)Wet weather water quality data at one station (El Camino Real Bridge): 1998 2006 (25 observations)

Mean Daily FlowModel Outlet 1007 vs. Agua Hedionda Creek At El Camino Real Bridge

Seasonal Regression and Temporal AggregateModel Outlet 1007 vs. Agua Hedionda Creek At El Camino Real Bridge

BMP RepresentationTwo general types of BMPs represented in the modelHydrologic Source Control (HSC)Storm Water Treatment (SWT)HSC reduces runoff volumes and rates primarily through infiltrationExamples may include vegetated swales*, biofilters, infiltration basins, permeable pavement, media filtersSWT removes pollutants after they have entered concentrated flow pathsExamples may include extended dry detention*, constructed wetlands, wet ponds, hydrodynamic devices, catch basins

* Most common in Agua Hedionda

Interpretation of SW RequirementsExisting treatment was determined through a review SUSMP BMPs and from information provided by Carlsbad on older detention pondsSDRWQB Order 2001-01: requires water quality treatment for priority projects (either volume- or flow-based wq treatment)Future priority projects must meet Order 2001-01 plus the 2007 OrderPeak flow control for continuous range of storms (channel protection-based requirement)LID practices (level of requirement unclear)Assumed that Priority Projects receive treatment in all future development except for Very Low Density (>1ac) and approximately half of Low Density (0.5-1.0ac)

Stream SegmentStormwaterTreatment 2EffluentConc.Untreated BypassStormwaterTreatment 1EffluentConc.Untreated BypassOverflowInfiltration goes to nearby urban pervious baseflow Drainage Area boxes represent a mix of land use.UntreatedHydrologic Source ControlImpervious55%5%40%55%30%10%5%Existing Scenario

Future ScenarioStream SegmentStormwaterTreatment 3EffluentConc.Untreated Bypass100%OverflowDrainage Area boxes represent different land uses developed in the future.Hydrologic Source ControlImperviousToSWT3ToHSC1Variable %Variable %+Infiltration goes to nearby urban pervious baseflow Existing ConfigurationModerate levels of LID application applied in the form of 4-10% impervious reduction.

Three Scenarios Predevelopment Existing Condition Future Conditions w/ BMPs Future Conditions w/o BMPs

Storm Hydrograph2/12/2001 - 2/14/2001

Sediment Loading at Lagoon

Next StepsIntegrate with geomorphic analysisFinal QA/QC, generate additional model output, and develop model reportUse model output to target and re-prioritize management recommendations in the WMP (e.g., priority subwatersheds, evaluate loading to lagoon, etc)

LID Constraints and Conceptual Designs

Future Developmentby Planned Land UseFuture Developmentby Planned Land Use

Constraints - SlopeAs slopes increase, many LID techniques become more difficult to implement0% to 15% - Low15% to 25% - Medium>25% - High (hillslope development)

Constraints - SlopeFor the majority of developing areas, slope is a low to medium constraintMany high slopes in areas planned for Very Low Density Residential.

Constraints - SlopeConstraints - Slope

Constraints Soil Erosion HazardSoil erosion hazard estimated to be mostly slight to moderateCorrelated to slopeSome localized hotspots

Constraints Soil Erosion HazardConstraints Soil Erosion Hazard

Constraints Soil InfiltrationIn most of the developing area, infiltration rates are very low In upper watershed, rates are better but still low

Constraints Soil InfiltrationLow and very low infiltration rates produce the biggest physical constraint to many important LID practicesNot feasibleDry wells/infiltration basinsMore costly to implement (need underdrains)Bioretention Permeable asphalt/concrete

Constraints Soil Erosion HazardConstraints Soil Infiltration

Other ConstraintsArid conditions/low rainfallConstraint for BMPs with permanent pools (wet ponds)Not a constraint for vegetation in BMPs, which can be maintained with irrigation/sprinklers

Conceptual DesignsVery low density residential in high sloped areasNot regulated as Priority ProjectsBest practice: Cluster development avoiding high slopes and riparian areasShared driveways and tucked-under parkingPermeable pavers for sidewalks/patiosCisterns used to supplement irrigation

Conceptual DesignsSingle Family ResidentialAvoid higher sloped/more erosive areas Riparian buffer setbacksVegetated or rock-lined swalesExtended Dry Detention BasinsShared driveways and tucked-under parkingPermeable pavers for sidewalks/patiosCisterns used to supplement irrigation

Conceptual DesignsHigh density mixed-use areas (commercial/multifamily)Vegetated or rock-lined swalesExtended Dry Detention BasinsBioretention (with underdrains)Turf block fire lanesRoof drains diverted to large flat pervious areasCisterns used to supplement irrigation (can be large and incorporated into building design)

Conceptual DesignsWarehouse/industrialVegetated or rock-lined swalesExtended Dry Detention BasinsTurf block fire lanesRoof drains diverted to large flat pervious areasCisterns used to supplement irrigation (can be large and incorporated into building design)

Evaluation Process for Identifying Acquisition, Restoration, and BMP Retrofit Opportunities

Land Acquisition and RestorationIdentifying opportunities forLand Acquisition for PreservationBuffer RestorationWetlands Restoration

Prioritizing opportunities based on Goal #2Considering Goal #3 in relation to water quality benefits

Goal #2 and ObjectivesProtect , restore and enhance habitat in the watershed.Protect and expand undeveloped natural areas to protect habitat.Protect, enhance, and restore terrestrial habitat, especially existing vegetation in riparian areas.Provide riparian habitat to improve and maintain wildlife habitat.Provide natural area connectivity to improve and maintain wildlife habitat.Maintain stable stream banks and riparian areas to protect instream aquatic habitat and priority tree species.Maintain and protect instream habitat to support native aquatic biology.Maintain and protect lagoon habitat.

Goal #3Restore watershed functions, including hydrology, water quality, and habitat, using a balanced approach that minimizes negative impacts.

ApproachIdentify subwatersheds with highest quality natural areas and wildlife habitat Priority SubwatershedsPrioritize preservation and restoration opportunities byPriority SubwatershedsScreening criteria that measure likelihood of achieving Goal #2 and providing water quality benefits

Priority Subwatershed Screening CriteriaNatural Areas naturally vegetated areasTerrestrial Habitat natural areas and undeveloped, disturbed land that provide wildlife habitat (e.g., agriculture) Riparian Habitat land that supports riparian vegetationCRAM Ratings of wetland function. Aquatic Habitat Rating Qualitative ratings from field reconnaissance. MSCP/MHCP Priority Species ObservationsLagoon/Coastal Subwatersheds Used to further prioritize lagoon and coastal habitat. Soil Erosion Hazard Rated by NRCS index as having severe or very severe erosion hazard

Comparison to MHCP and MSCPMultiple Habitat and Species Conservation Plans (MHCP and MSCP)Checked that connectivity provided between:MHCP/MSCP planning, core, and linkage areas AH priority subwatersheds

Land Acquisition Screening CriteriaLocation within a Priority Subwatershed Unprotected Natural Areas naturally vegetated areas that may be developed in the future. Riparian Habitat land that supports riparian vegetation.Location Relative to a Stream Restoration OpportunityLocation relative to invasive species treatment areasSoil Erosion Hazard land rated by NRCS index as having severe or very severe erosion hazard.

Used to prioritize parcels for preservation

Buffer Restoration Screening CriteriaLocation within Priority and Linkage Subwatersheds Priority subwatersheds that provide opportunities to restore habitat connectivity. Buffer Restoration Opportunity undeveloped land that is likely to support riparian vegetation and is not within the existing natural areas. Location Relative to a Stream Restoration OpportunityLocation Relative to Priority Tree Species considered Coast Live Oak, Sycamore, and Cottonwood dominated riparian communities.

Buffer Restoration Screening Criteria (Cont.)Road and Bridge Constraints Prioritized opportunities with fewer constraintsSewer Line Constraints Same as above

Used to prioritize parcels for buffer restoration

Wetland Restoration Screening CriteriaLocation within Priority and Linkage Subwatersheds Subwatersheds that provide opportunities to restore habitat connectivity. Wetland Restoration Opportunity undeveloped land that where wetlands may have been disturbed or destroyed. CRAM Code Ratings of wetland function. Location relative to stakeholder recommended opportunitiesLocation within coastal subwatersheds

Used to prioritize parcels for wetlands restoration

Scoring MethodsDeveloped metrics from screening criteriaDeveloped scoring thresholdsScored subwatershed or parcel from 1 to 10 pointsCalculated composite score over all metrics for:Subwatershed PriorityLand AcquisitionBuffer RestorationWetland Restoration

Preliminary Land Acquisition Opportunities

Total Opportunity Area: 2,700 acres of unprotected natural areaParcels with >10 ac unprotected natural area: nearly 1400 acresTop Ranking Parcels: 123 acres of unprotected natural area with 57 acres of riparian habitat

Preliminary Buffer Restoration Priorities[Insert Map]Buffer Restoration Priorities

[Insert Map]Wetland Restoration Priorities

Verification and Cost EstimationFor top-ranking sites, verifying land cover with 2005 Aerial PhotographsVerifying that scoring system identifies appropriate opportunitiesEstimating planning-level acquisition and restoration costs

End ProductsDatabase of all opportunities with ownership information, metrics, and scoresDetailed location mapsList of stakeholder recommended opportunities

Stream Restoration and BMP Retrofit Screening CriteriaEffectiveness in addressing existing or potential water quality, geomorphology, or habitat problems. FeasibilityStream reach lengthCurrent land coverMinimal landownersSite accessMinimal utility or flood control constraintsUpland sources of degradation that would prevent long-term successMeets multiple goals/objectives Relative costStakeholder support. Including TAC and WPG

Finalizing Goals and Objectives

Goal #4Support compliance with regional, state, and federal regulatory requirements applicable to the watershed

Goal 4 Draft ObjectivesAssist in meeting regional water quality objectives.Leverage efforts in helping meet local requirements.Support information sharing so stakeholders are knowledgeable.

Goal 4 Draft Objectives, cont.Maintain an open process regarding regulatory requirements and compliance. Achieve compliance with local and regional water quality objectives.Provide feedback and reporting mechanisms.

Goal #5Increase awareness and stewardship within the watershed, including encouraging policy makers to develop policies that support a healthy watershed.

Goal 5 Draft ObjectivesDisseminate information to stakeholders to support scientifically based, sound decision-making.Develop a consistent and coherent message about the watershed based on sound science.Support citizen stewardship though public education and outreach.

Goal 5 Draft Objectives, cont.Support adoption and implementation of a Watershed Management Plan by local jurisdictions, agencies, and environmental organizations.Sustain long-term watershed management through a collaborative Agua Hedionda Watershed Council.

Next Steps

Irrigation water is from outside source.Star marks outlet of subwatershed # 1007 29 subwatersheds (not including the beach watershed, model ID 999) used in the model with an average size of 1.1 mi2 and covering an area of 31 mi2.

SELC Flow data collected at El Camino Real Bridge: Due to a City dredging operation, the stream gauge was not operational 3/6 - 6/24/2006; Rating curves for converting stream level to discharge have likely been altered since 3/6/2006.

Wet weather station also co-located with a dry weather station. Only a few observations.

Also includes SWAMP data but there is very little.

Note sure what is causing the lower than observed flow in November. Rainfall datawe are using data from only one station. Uncertainty about irrigation (amounts, etc.)Only showing results for sediment today: relevant to lagoon impairment and stakeholders habitat goals and objectives.TSS data in the watershed available for only one station. Calibration limited by (1) the temporal and spatial limits of the available data and (2) lack of detailed stream morphology data.

Note: that we are comparing model output (suspended sediment) to observed TSS (suspended solids).

We are showing simulated CONCOUT: the flow-weighted average concentration for the day flowing OUT of the stream.

Graph comparing observed and simulated loads (calculated with simulated flow). There is some scatter about the 1 to 1 line.In a typical storm water quality improvement project, a combination of HSCs and SWTs are used.Note: SUSMP BMP information only provided by Vista; general application info. provide by CountyPriority project assumption based on communication with CountyPeak flow applied here controls 2 to 15 year storm peaksWe apply a modest LID effect (not including the swales and similar devices) in the form of impervious cover reduction (4 to 10% reduction).This is an example of how Urban BMPs are addressed in the model for the Existing Scenario. Within a subwatershed, the landuse areas are redistributed according to the treatment they undergo. Existing treatment was determined through a review of SUSMP BMPs (Only provided by Vista; assumed that trends in Vista hold true throughout the watershed) and from information provided by Carlsbad on older detention ponds.

HSC represent lands that are subject to hydrologic source control, which involves providing opportunity for additional infiltration (HSC1 is a vegetated swale). HSC1 may also represent biofilters, infiltration trenchs and pervious pavement. SWT represents traditional stormwater treatment devices. SWT1 is extended detention pond based on 2001 order requirements (wq treatment). SWT2 represents a variety of devices: CDS, Vortex, Catch Basins. Treatment is less 2% of watershed area. Effluent concentrations from CASQA BMP manual and ASCE database.

BMP Designs based on 2001 Order, CASQA BMP Manual, and San Diego Hydrology Manual.

Note that in the existing scenario, 30% of the developments b/w 2002 and 2007 received no treatment either because they were not required or because relatively ineffective treatments were used (e.g., drain inserts). There appeared to be a progression in the SUSMP BMPs will little application in 2002 and 2003 and more common implementation of swales and detention toward 2007.

In the Future Scenario, prior developed land from the Existing Scenario is treated as it was except for identified Vista redevelopment areas. Future Development must meet the 2001 requirements (wq treatment) plus the 2007 order (added Hydro requirement to control peaks and has LID requirements though the precise nature of how much LID is required is fuzzy).

LID: assumed a moderate to level implementation including decreased imperviousness and disconnection. Impervious reductions of 9 to 10% except for Heavy Commercial (3.5%) and Industrial (4%).

Based on our understanding of what Priority Projects receive treatment, all future development except for Very Low Density and half of Low Density (personal communication with County) is assumed to be treated by SWT3 (here assumed to be an extended dry dentition with peak controlthis is an enlarged SWT1). A portion of the developments can use swales and similar devices (HSC1) and is variable by land use.HSC1 = 10% to 75% application variable by land useSWT3= all Priority development is treated by SWT3 (25% to 90% goes straight to SWT3)Effluent concentrations from CASQA BMP manual and ASCE database.BMP Designs based on 2007 Order, CASQA BMP Manual, and San Diego Hydrology Manual.Greater than 25% of watershed is treated in the future scenario.Output at El Camino Real Bridge (Model id 1007).

Rainfall:2/12/20010.302/13/20012.00(near the 2 yr/24 hr storm rainfall amount)

Peak is controlled in future. But notice extended duration of erosive flows (see orange tail). Does the watershed need additional volume-based control for channel protection?Output at top of lagoon (Model sub 1004). Represents most of the watershed loading to the lagoon.

Average annual based on 10 years (1997 2006).

Note that the Bioengeinnering The highlighted words were key terms that we used to select appropriate screening criteria. We started with the list of screening criteria developed previously and selected screening criteria that best measured how preservation and vegetation restoration could achieve this goal and associated objectives.

(We used most of the previously selected screening criteria, but a few were more relevant to stream restoration and BMP retrofits. We also added a few more screening criteria.)

Although policies will be recommended in the watershed plan to accomplish this goal, we did consider how the water quality benefits of the opportunities will help support the achievement of this goal. The priority subwatersheds were used to prioritize opportunities, both preservation and restoration, that would increase connectivity of existing protected habitat. Using 1995 vegetation data for all land cover. Verifying vegetation with aerial photos for top-ranking sites. The CRAM ratings came from Meleahs field work. Dave developed the Aquatic Habitat Ratings.We did not use the biological monitoring data because there was not enough variation in the ratinings (either poor or very poor) and the sites were concentrated in one part of the watershed.

Screening criteria were used to develop scores for each type of management.

Double weight was given to these metrics:Percent natural area in subwatershed (priority subwatersheds metric)Percent natural area in parcel (land acquisition metric)Percent of watershed-wide buffer restoration opportunity within subwatershed (buffer restoration metric)Percent of watershed-wide buffer restoration opportunity within parcel (buffer restoration metric)Percent of watershed-wide wetlands restoration opportunity within parcel (wetlands restoration metric)

Note that some of this land may already be developed. We will verify land cover for the top ranking parcels. 55 properties have >10 ac unprotected natural area15 top ranking parcels

These products will be produced alongside the watershed management plan (after the acquisition and restoration report). Note that, for the land acquisition and any other sensitive properties, Meleah is working on a way to safely share this information to resource agencies and conservation organizations.

The list of stakeholder opportunities are the properties that Meleah and I gathered from contacting the WPG, resource agencies, and conservation groups. Based on reviewing your discussions and the project scope of work, we added a new goal.

This is very key because it gives a context we need to be aware of and work within beyond the other goals and objectives. It will also show local officials HOW this plan can help them meet requirements and perhaps make them even more supportive and engaged.Photo: Example of Low Impact Development (narrow streets, pervious side walk, open space) in Hercules, CA

This goal merges two of your preliminary goals:Increase awareness and stewardshipEncourage stakeholders to develop policies that support a healthy watershed.We found the latter goal to be part of increasing awareness and stewardship.