United States

Department of

Agriculture

Forest

Service

May 2014

DRAFT Geology Report Salmon Salvage Salmon/Scott River Ranger District

Siskiyou County, California

For Information Contact: Angie Bell

1711 So. Main Street, Yreka, CA

albell@fs.fed.us

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Table of Contents Methodology.................................................................................................................. 3

Analysis Indicators ...................................................................................................................... 3 Spatial and Temporal Context ..................................................................................................... 3

Affected Environment ................................................................................................... 3

Environmental Consequences ..................................................................................... 4 Alternative 1 -No Action ............................................................................................................. 4

Compliance with law, regulation, policy, and the Forest Plan……………………….4 Alternative 2 ................................................................................................................................ 5

Compliance with law, regulation, policy, and the Forest Plan……………………….6 Alternative 3 ................................................................................................................................ 6

Compliance with law, regulation, policy, and the Forest Plan……………………….7

Literature Cited ............................................................................................................. 7

Table of Tables Table 1: Risk matrix uses potential versus consequence to assess risk of a landslide event in a 7th field

watershed. ............................................................................................................................................. 8

Table 2: Current condition CWE modeling output for the geo model (landslide potential) for the project area. Output volume from model is in cubic yards/decade. The risk ratio is a unitless relative measure of landslide potential............................................................................................................... 9

Table 3: Alternative 2 CWE modeling output for the geo model (landslide potential) for the project area. Output volume from model is in cubic yards/decade. The risk ratio is a unitless relative measure of landslide potential. ................................................................................................................................ 9

Table 4: Alternative 3 CWE modeling output for the geo model (landslide potential) for the project area. Output volume from model is in cubic yards/decade. The risk ratio is a unitless relative measure of landslide potential. .............................................................................................................................. 10

Table of Figures Unstable Lands Map……………………………………………………………………………..14

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Geology Report The purpose of this report is to analyze the effects of the Salmon Salvage Project on slope stability.

METHODOLOGY Three days of field review were completed to validate geologic and geomorphic mapping. Unstable lands are designated as Riparian Reserves in the Forest Plan (Standard and Guideline MA 10-2, pg. 4-108). The unstable lands component of Riparian Reserves includes active landslides, inner gorges, toe zones of dormant landslides and severely weathered and dissected granitic lands. See map in appendix C for location of unstable lands in the project area.

The Cumulative Watershed Effects Geo model is used to estimate the landslide potential. The model uses mapping of the geomorphology, past and present disturbances, and coefficients developed using research on the effects of the 1964 flood event on landslide rates. The output from the model is volume of sediment delivered to the mouth of the 7th field watershed during a 10-year storm event (cubic yards per decade). The volumes are converted into a risk ratio to estimate landslide potential across the Forest and among project alternatives. A threshold of concern for the risk ratio is 1.0. This is not the point at which significant effects occur but a yellow flag indicating that additional impacts need to be considered closely for resource degradation and impacts to beneficial uses of water. Watersheds with proposed activities that are over the threshold of concern will consider mitigations to prevent unacceptable negative impacts. A more detailed description of the cumulative watershed effects modeling process is available in a Forest-wide document (Bell, 2013).

Analysis Indicators The indicator used for this analysis for effects to geology is landslide risk. Risk is the intersection between the potential of landsliding and the consequence of landsliding. Landslide potential is estimated from the GEO model risk ratio. Consequences analyzed include: 1) Impacts to human health and safety, 2) Impacts to infrastructure, and 3) Impacts to natural resources. Landslide risk ranges from Very High, which indicates an immediate need for mitigation of the risk, to Very Low, which indicates a nuisance disruption. See appendix A for details.

Spatial and Temporal Context The spatial scale for the landslide risk and cumulative effects analysis is the 7th field watershed because the models used for analysis are calibrated at the 7th field scale. The temporal scale is from the present to ten years for short-term and 10-50 years for long-term. Elevated landslide rates due to forest management in Northern California have been shown to begin to decrease around 7-12 years after a disturbance and recover in about 50 years (Ziemer, 1981 and de la Fuente & Haessig, 1994).

AFFECTED ENVIRONMENT The western portion of the project area, Little North Fork, is underlain by highly weathered granitic rocks, commonly referred to as decomposed granite. This bedrock is prone to shallow landsliding (debris slides and debris flows) and is highly sensitive to disturbance such as wildfire

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and road construction. The eastern portion is underlain by dormant landslides of about 0.5 square miles in area. There are 12,684 acres of unstable lands, including 5,192 acres of severely weathered and dissected granitic land in the project area. See appendix C for the unstable lands map. Based on the Burned Area Reflectance Classification model for soil burn severity, the Salmon Complex fire area had: 20% unburned/very low severity; 53% low severity; 22% moderate severity; and 5% high severity. The GEO risk ratio is elevated over the threshold of concern due to the wildfire effects (Table 1). The North Fork Roads project and the Burned Area Emergency Response road work are considered complete in the cumulative watershed effects modeling and are included in the current condition of the watershed in the GEO model. The related road work reduced the landslide potential by 2% 7% and 9% for the Olsen, Shiltos and Little North Fork creeks respectively.

Under current conditions, the landslide potential of the Olsen Creek watershed is “Highly Likely;” for Shiltos and Lower Little North Fork it is “Likely.” The landslide risk of the Olsen Creek watershed is “High” and for Shiltos and Lower Little North Fork it is “Moderate.” Environmental Consequences

ENVIRONMENTAL CONSEQUENCES Alternative 1 -No Action Direct and Indirect Effects There are no direct effects to landslide potential under this alternative. The area will recover naturally including the re-establishment of vegetation and ground-cover, increasing root support and interception of precipitation which reduces landslide risk and potential. Prolonged hardwood and brush dominated occupancy will not provide the root support to maintain stable slopes (Jackson & Roering, 2009). The project area may take up to 50 years to recover to a pre-fire landslide risks level.

Cumulative Effects The effects of past actions and events on the landslide risk and potential of the project area are included in the affected environment. There are two ongoing or reasonably foreseeable future actions that will be considered for cumulative effects within the 7th field watersheds analyzed for this project: Salmon Reforestation and Jess projects. The Salmon Reforestation project will increase reforestation rates, thereby speeding up the landslide risk recovery in the 7th field watersheds analyzed. The GEO risk ratios will not be increased by adding the effects of alternative 1 to those of the Salmon Reforestation project. The Jess project increases the landslide volume by less than 0.5% in Shiltos and Olsen Creek 7th field watersheds. Although adding the modeled effects of the Jess project to the effects of alternative 1, the increase in landslide risk will be minimal because the model does not account for implementation of project design features intended to minimize impacts to unstable lands and landslide risk.

Compliance with law, regulation, policy, and the Forest Plan The project is compliant with the Klamath National Forest Plan (1995, as amended) Standards and Guidelines. A geologic investigation was completed and natural regeneration of vegetation

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on unstable lands will improve slope stability in the project area but recovery could take up to 50 years.

Alternative 2 Direct and Indirect Effects No active landslides, toe zones of dormant landslide deposit or inner gorges will be entered by tractors and mechanical harvesters. Disturbance by cable corridors will be minimized by partial suspension, water dispersion on the corridors and corridor placement (watershed project design features in chapter 2 of the Environmental Assessment) in these unstable lands. There will be 136 acres of fire salvage in the unstable lands component of Riparian Reserves; 93 acres on severely weathered and dissected granitic lands and 43 acres on inner gorges and active landslides which are contained within the inner gorges. There are 430 acres of roadside treatment on unstable lands, with 284 of the acres being on severely weathered and dissected granitic lands and 134 in inner gorges (see Unstable Lands map, appendix C). There are nine acres of treatments planned on small (about 0.5 acres), shallow debris slides that are mainly within inner gorges. Project design features (chapter 2 of this EA) limiting disturbance in inner gorges will minimize impacts to this unstable lands component of the Riparian Reserve. The likelihood of increasing instability on three acres of dormant landslide toe zones in roadside units is very low because of the exclusion of tractors and mechanical harvesters. The direct effect of the removal of fire salvage trees is disturbance of the soil during harvest by tractors and in cable corridors. If not mitigated, these practices can concentrate water on the hillslope which will increase landslide potential. This is not different from the impacts during green tree sales and will be minimized as a result of project design including the limitations on the use of equipment and placing corridors in stream channels and on steep slopes.

Indirect effects of removing dead fire-killed trees could potentially increase landslide potential in the short term, mainly due to the re-opening or construction of new landings. The GEO model estimates that the landslide potential will increase by 2,148 cubic yards per decade, 1,547 cubic yards per decade, and 1,991 cubic yards per decade for the Lower Little North Fork, Shiltos and Olsen Creek watersheds. The increase is attributed completely to the landing re-opening and construction needed to implement this alternative. This increases the risk ratio for the GEO model by 0.1 for all watersheds. However implementation of project design features will minimize project-related landsliding from landings.

Removal of fire-killed trees is not likely to cause measurable changes in hillslope hydrology as these trees no longer transpire or intercept precipitation. In the long term, reduction of snags will result in a reduction in down large wood on hillslopes. This will have some potential for increasing surface erosion but will also result in less water infiltrating into the hillslope due to the interception effect of the logs, and groundwater is an important trigger for landsliding. However, slash from salvage logging will enhance infiltration of water into soils but at the same time, protect soils from rilling, gullying, and shallow landslides.

Indirect effects of cable yarding are less than those caused by tractor logging as ground disturbance will be minimal with the implementation of the project design features. Indirect effects from helicopter yarding will be similar to those from cable yarding, but much smaller due to no opportunity for logs to be dragged as they are yarded.

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Indirect effects of new landing construction and re-opening of roads include elevated landslide potential due to changes in mass balance associated with cuts and fills and by modifying natural patterns of drainage on hillslopes. Under current conditions the temporary roads on existing roadbeds are attributing 19 cubic yards per decade and 15 cubic yards per decade to the landslide potential in the Shiltos and Olsen Creek watersheds respectively. The post-treatment hydrologic stabilization will improve slope drainage and reduce landslide potential by 14 cubic yards per decade and ten cubic yards per decade. Road maintenance and correction of legacy sediment sources along the roadways will correct surface drainage problems, reduce concentration of water, and thereby reduce landslide potential and sedimentation of nearby drainages.

The estimated landslide volume is increased by 9%, 2%, and 4% for the Shiltos, Olsen and Lower Little North Fork Creek, respectively, due to this alternative for the GEO model (see Table 3 in appendix B). This will not increase the landslide potential for the watersheds. The landslide risk will remain high for Olsen Creek and moderate for Shiltos and Lower Little North Fork.

There is also a beneficial effect on landslide risk as a result of the harvesting of fire-killed trees. Fire-killed trees do not intercept precipitation and the roots will decay at the same rate whether the tree remains standing or is harvested (Jackson & Roering, 2009). It can take up to 50 years for the landslide potential to naturally and fully recover to pre-fire conditions (de la Fuente & Haessig, 1994). The salvage of fire-killed trees will accelerate the re-establishment of conifer forest in the project area compared to areas without salvage which will accelerate the reduction of landslide potential on unstable lands.

Cumulative Effects The effects of past actions and events on the landslide risk and potential of the project area are included in the affected environment. There are two ongoing or reasonably foreseeable future actions that will be considered for cumulative effects within the 7th field watersheds analyzed for this project: Salmon Reforestation and Jess projects. The Salmon Reforestation project will increase reforestation rates, thereby speeding up the landslide risk recovery in the 7th field watersheds analyzed. The modeled GEO risk ratios will be increased by 0.1 by adding the effects of alternative 1 to those of the Salmon Reforestation project (see Table 3). The Jess project increases the landslide volume by less than 0.5% in Shiltos and Olsen Creek 7th field watersheds. Although adding the modeled effects of the Jess project to the effects of alternative 2, the increase in landslide risk will be minimal because the model does not account for implementation of project design features intended to minimize impacts to unstable lands and landslide risk.

Compliance with law, regulation, policy, and the Forest Plan The project is compliant with the Klamath National Forest Plan (1995, as amended) Standards and Guidelines. A geologic investigation was completed and vegetation on unstable lands are being managed protect slope stability.

Alternative 3 Direct and Indirect Effects The impacts of removing only roadside hazard trees will not measurably increase the landslide potential at all. The landslide potential as modeled by the GEO will remain the same as for

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alternative 1 (see Table 4 appendix B). There will be no hydrologic stabilization of the two temporary roads on existing roadbeds, so the 34 cubic years per decade that they currently attribute combined to the landslide potential will not be mitigated. The main savings in landslide potential between alternative 2 and alternative 3 is that no landings will be re-opened or constructed in alternative 3. The landslide risk will remain unchanged from current conditions: High for Olsen Creek and Moderate for Shiltos and Lower Little North Fork Creeks.

There will be no benefit to landslide risk from this alternative because there will be no increase in the rate of re-forestation as a result of hazard tree removal only.

Cumulative Effects The cumulative effects of adding the effects of this alternative to those of Salmon Reforestation will not increase the risk ratio for any of the watersheds analyzed (see appendix B, Table 4). The cumulative effects of adding the effects of the Jess project to those of this alternative will be the same as for alternative 2.

Compliance with law, regulation, policy, and the Forest Plan The project is compliant with the Klamath National Forest Plan (1995, as amended) Standards and Guidelines. A geologic investigation was completed and natural regeneration of vegetation on unstable lands will improve slope stability in the project area but recovery could take up to 50 years.

LITERATURE CITED Bell, A. 2013. Cumulative Watershed Effects Summary. Klamath National Forest, Siskiyou

County, California.

de la Fuente, J. and Haessig, P. 1994. Salmon Basin Sediment Study. USDA, Klamath National Forest, unpublished document.

Jackson, M., Roering, J. 2009. Post-fire geomorphic response in steep, forested landscapes: Oregon Coast Range, USA. Quaternary Geology.

Parise, M., Cannon, S. 2012. Wildfire impacts on the processes that generate debris flows in burned watersheds. Natural Hazards.

Shakesby, R., Doerr, S. 2006. Wildfire as a hydrological and geomorphological agent. Earth-Science Reviews.

Swanson, F. 1981. In: Proceedings, Fire Regimes and Ecosystems conference, December 11-15, Honolulu, HI. General Technical Report, WO-23, Washington, DC.

Ziemer, R. 1981. The role of vegetation in the stability of forested slopes. Pacific Southwest Research Station, Arcata, CA.

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Appendix A: Landslide Risk Analysis Table 1: Risk matrix uses potential versus consequence to assess risk of a landslide event in a 7th field watershed.

Almost Certain

Highly likely Likely Unlikely Rare

Catastrophic Consequences Very High Very High High Moderate Moderate

Major Consequences Very High High High Moderate Low

Moderate Consequences High High Moderate Moderate Very Low

Minor Consequences High Moderate Low Low Very Low

Nuisance Consequences Low Low Very Low Very Low Very Low

The Risk Category Implications

a) Very High – Health and human safety or essential infrastructure is at risk. There is an immediate and urgent need to reduce the likelihood of landsliding or mitigate the consequence to the elements at risk.

b) High – There is a reasonable probability that landsliding will impact essential infrastructure and may impact health and human safety. Non-essential infrastructure as well as recreation and visitor use may be impacted.

c) Moderate - There is a moderate probability of impacts to essential or non-essential infrastructure or health and human safety as a result of landsliding. The cost and benefit of mitigations need to be considered before proposal for implementation.

d) Low – There a low probability of impacts to Elements at Risk. Remediation of landsliding consequences may be the most cost effective method of dealing with these areas.

e) Very Low – There is almost no probability of impacts to Elements at Risk as a result of landsliding. Mitigations are rarely needed.

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Appendix B: Cumulative Watershed Effects – landslide model Table 2: Current condition CWE modeling output for the geo model (landslide potential) for the project area. Output volume from model is in cubic yards/decade. The risk ratio is a unitless relative measure of landslide potential.

HUC14 7th field name Background Harvest and Fire (from 1964 to 2014)

Roads Total Landslide Volume

Risk Ratio

18010210020706

Shiltos Creek-North Fork Salmon River

Shiltos Creek-North Fork Salmon River

7331

1494

8394 17219 0.7

18010210020801

Olsen Creek-North Fork Salmon River

18624 51088 13462 83170 1.7

18010210020604

Lower Little North Fork Salmon River

12221 15542 13187 37841 1.0

Table 3: Alternative 2 CWE modeling output for the geo model (landslide potential) for the project area. Output volume from model is in cubic yards/decade. The risk ratio is a unitless relative measure of landslide potential.

HUC14 7th field name Background Total Landslide Volume

Alt. 2 Future Actions

Risk Ratio

18010210020706

Shiltos Creek-North Fork Salmon River

Shiltos Creek-North Fork Salmon River

7331

17219 1552 69 0.8

18010210020801

Olsen Creek-North Fork Salmon River

18624 83170 1996 12 1.8

18010210020604

Lower Little North Fork Salmon River

12221 37841 2148 0 1.1

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Table 4: Alternative 3 CWE modeling output for the geo model (landslide potential) for the project area. Output volume from model is in cubic yards/decade. The risk ratio is a unitless relative measure of landslide potential.

HUC14 7th field name Background Total Landslide Volume

Alt. 3 Future Actions

Risk Ratio

18010210020706

Shiltos Creek-North Fork Salmon River

Shiltos Creek-North Fork Salmon River

7331

17219 0 69 0.7

18010210020801

Olsen Creek-North Fork Salmon River

18624 83170 0 12 1.7

18010210020604

Lower Little North Fork Salmon River

12221 37841 0 0 1.0

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Appendix C: Unstable Lands Map