Geology Report -...

United States Department of Agriculture Forest Service November 2013

Draft Geology Report Jess Project

Salmon/Scott River Ranger District, Klamath National Forest Siskiyou County, California

For Information Contact: Angie Bell, Forest Geologist 1711 S. Main Street, Yreka, CA 96097

530-841-4583

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or part of an individual’s income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD).

To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410, or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer.

i

Table of Contents Executive Summary ..................................................................................................................... 3

Methodology ........................................................................................................................... 3 Overview of Methodology .................................................................................................. 3 Analysis Indicators.............................................................................................................. 3 Spatial and Temporal Context ............................................................................................ 4

Affected Environment ............................................................................................................. 4 Environmental Consequences ................................................................................................. 4

Alternative 1........................................................................................................................ 4 Direct Effects and Indirect Effects .................................................................................. 4 Cumulative Effects.......................................................................................................... 5



Summary of Effects ............................................................................................................ 6 Compliance with law, regulation, policy, and the Forest Plan ........................................... 7

Geology Report............................................................................................................................ 8 Introduction ............................................................................................................................. 8 Proposed Actions and Alternatives Analyzed......................................................................... 8 Methodology ........................................................................................................................... 8

Analysis Indicators.............................................................................................................. 9 Spatial and Temporal Bounding of Analysis Area ........................................................... 10

Affected Environment ........................................................................................................... 10 Environmental Consequences ............................................................................................... 13

Alternative 1...................................................................................................................... 13 Direct Effects and Indirect Effects ................................................................................ 13 Cumulative Effects........................................................................................................ 13

Alternative 2...................................................................................................................... 13 Direct and Indirect Effects ............................................................................................ 13 Cumulative Effects........................................................................................................ 14

Alternative 3...................................................................................................................... 15 Direct and Indirect Effects ............................................................................................ 15 Cumulative Effects........................................................................................................ 16

Compliance with law, regulation, policy, and the Forest Plan ......................................... 17 Literature Cited ..................................................................................................................... 18 Appendix A – Landslide Risk Assessment ........................................................................... 19 Appendix B: Unstable Lands and Headwaters Analyzed ..................................................... 24

ii

List of Tables Table 1: Landslide volumes estimated by CWE GEO model for the watershed in the project area under

current conditions. ............................................................................................................................... 10 Table 2: Landslide likelihood analysis for affected environment. .............................................................. 11 Table 3: Overall landslide risk assessment for affected environment under current conditions for 7th field

watersheds. .......................................................................................................................................... 12 Table 4: Summary of CWE GEO modeling for current conditions in the affected environment. .............. 13 Table 5: Landslide volume as estimated by the CWE GEO model for alternative 2. ................................. 13 Table 6: Landslide likelihood analysis for alternative 2. ............................................................................ 14 Table 7: Overall landslide risk assessment for Alternative 2. ..................................................................... 14 Table 8: Cumulative Watershed Effects GEO model results for Alternative 2. ......................................... 15 Table 9: Landslide volume as estimated by the CWE GEO model for alternative 3. ................................. 15 Table 10: Landslide likelihood analysis for alternative 3. .......................................................................... 16 Table 11: Overall landslide risk assessment for alternative 3. .................................................................... 16 Table 12: Cumulative Watershed Effects GEO model results for Alternative 3. ....................................... 17 Table 13: the landslide risk matrix shows how likelihood is compared with consequence to determine the

landslide risk. The likelihood is based on GEO-CWE results and landslide history and consequences based on the Elements at Risk. ............................................................................................................ 22

List of Figures Map 1: Unstable lands and headwaters analyzed in Environmental Effects section of this report. ............ 24

Geology Jess Project

3

Executive Summary The Forest Service Manual Chapter 2880 (Geologic Resources, Hazards and Services) requires the assessment of the risk of loss of life, property and natural resources from both naturally-occurring and management related landslides. The risk must be minimized or mitigated when possible. The Klamath National Forest Land and Resource Management Plan (LRMP) directs the interdisciplinary team (IDT) to manage vegetation on unstable lands to maintain or enhance slope stability (LRMP Standard and Guideline 2-1). Project-level review of the unstable lands is required to validate the current mapping (LRMP Standard and Guideline 2-2). Unstable lands are defined as active landslides, inner gorges, toe zones of dormant landslides and severely-weathered and dissected granitic lands. These features are considered Riparian Reserves (LRMP Standard and Guideline MA 10-2).

Methodology Overview of Methodology Field reviews were completed to validate existing geomorphic mapping and to determine if treatment on unstable lands was appropriate to maintain or enhance slope stability. Landslide rates are affected by vegetation management activities by the concentration of surface water on hillslope, reduction in root support and reduction in interception of precipitation by vegetation. Landslide rate is indirect effected by some forest management activities and is difficult to measure directly due to the complex and stochastic nature of these events. The analysis indicators analyzed are proxies for such processes. A landslide event is defined for this analysis as large-scale, extensive episode resulting in several landslides that could interrupt ingress/egress, fluvial processes on 3-5th order streams or damage major infrastructure across a 7th field watershed.

Analysis Indicators Landslide volume is estimated by the Cumulative Watershed Effects Geology (CWE GEO) model (CWE report) and represents the magnitude of a landslide event. This indicator uses the empirical mathematical GEO Cumulative Watershed Effects (CWE) model to estimate the volume of sediment delivered to the mouth of a 7th field watershed due to all types of landsliding during a 10-year storm event. The coefficients in the mathematical equation were developed in the Salmon River basin and the model assumes the geomorphic landforms react identically regardless of elevation. The indirect effects will be analyzed using the landslide volume estimates attributed to the alternative relative to the existing condition volume estimates.

Landslide risk is the chance of effects of injury or loss as a measure of the probability and adverse consequences to safety, property or natural resources. (See Appendix A of Geology Report). Landslide likelihood is determined by geomorphic landform, disturbance, landslide modeling, and road density. The analysis uses existing geomorphic mapping, bedrock mapping and historical landslide information to determine the likelihood of landsliding. The consequences of a landslide are based on the impacts to Elements at Risk. The Elements at Risk for this analysis are dispersed campsites, ingress/egress, Sawyers Bar municipal water source (Jessups Gulch), fish habitat and water quality in a Key Watershed (North Fork Salmon River).


4

The GEO CWE model risk ratio is used in the cumulative effects and is calculated as 2 times the “background” landslide volume over the current landslide volume. The threshold of concern for the risk ratio is 1.0. A risk ratio greater than or equal to 1.0 is a yellow flag and calls for a closer look at mitigation opportunities. See Cumulative Watershed Effects: the Abridged Version (Bell 2012).

Spatial and Temporal Context The spatial scale for analysis is the 7th field watershed scale for the direct/indirect effects and the cumulative effects. The models used for analysis are calibrated at a 7th field scale. The temporal scale is 0-10 years for short-term and >10 years for long-term. Elevated landslide rates due to forest management have been shown to begin to decrease around 7-12 years after the disturbance in Northern California.

Affected Environment The project area is within 4 7th field watersheds, Eddy Gulch, Jessups Gulch, Shiltos Creek and Olsen Creek.

The current landslide volumes estimated for the analysis area are about 16000 yd3/decade, 18400 yd3/decade, 17200 yd3/decade, and 83200 yd3/decade for Eddy Gulch, Jessups Gulch, Shiltos Creek, and Olsen Creek respectively. Ninety-eight, eighty-eight and eighty-five percent of the landslide volume from past management activities in Eddy Gulch, Jessups Gulch and Shiltos Creek are related to the existing road system respectively. The 2013 Salmon River Complex wildfire is the reason for almost seventy-five percent of the landslide volume modeled by the CWE GEO model.

The likelihood of a landslide event for Eddy Gulch and Jessups Gulch is likely. The likelihood of landsliding event is highly likely for Shiltos and Olsen Creek. Shiltos Creek has a high road density and Olsen Creek has an elevated CWE GEO risk ratio due to the 2013 Salmon Complex Wildfire. All of the watersheds have ingress/egress, fish habitat and water quality (not related to potable water) as Elements at Risk. Jessups Gulch also is a municipal watershed (potable water). There are a few dispersed campsites in the analysis area but they are set off of stream channels and are not likely to be impacted by landsliding. The landslide risk under current conditions is moderate in Eddy Gulch and high in the other three watersheds.

The risk ratios for Eddy Gulch, Jessups Gulch and Shiltos Creek are under the Threshold of Concern. Olsen Creek, however, has a risk ratio of 1.73 which is over the Threshold of Concern of 1.0. The elevated risk ratio is due to the effects of the 2013 Salmon Complex Wildfire that occurred on the northern half of the 7th field watershed outside of the project area.

Environmental Consequences Alternative 1 Direct Effects and Indirect Effects Under this alternative no management actions will occur. There are no direct or indirect effects to landslide volume or risk.


5

Cumulative Effects There are no direct or indirect effects for this alternative therefore there are no cumulative effects.

Alternative 2 Direct Effects and Indirect Effects The landslide volume for alternative 2 is increased by less than 1% for Eddy Gulch, Shiltos Creek and Olsen Creek 7th field watershed. The landslide volume is increased by almost 8% for Jessups Gulch. The modeling does not account for the project design features (Environmental Impact Statement, Chapter 2) prescribed to minimize the impacts of the project on Riparian Reserves. The treatments in inner gorges are limited by the commercial harvest and equipment exclusion zones. There is also a decrease in the road related landsliding volume as a result of the hydrologic stabilization of the temporary roads on existing roadbeds.

The percent of headwaters with harvest or burn and the CWE risk ratios are increased by the alternative but not enough to increase the overall landslide risk in any of the watersheds. The temporary roads on existing roadbeds are included in the current road density because they are currently in a drivable state and will require no earthwork to reopen for use. So the road density did not change at all by the alternative.

Jessups Gulch, Shiltos Creek and Olsen Creek have high landslide risk. According to the risk matrix (Appendix A of Geology Report) projects mitigations should be prescribed to mitigate impacts. There are 45 project design features prescribed in Chapter 2 of the Environmental Impact Statement (Watershed-1 through Watershed-45) that are intended to minimize impacts to watershed health and landslide rates.

Cumulative Effects The recent past and current actions include the North Fork Roads Stormproofing project, Eddy Late Successional Reserve Restoration project, Glassups project and the road work done under the Burned Area Emergency Response. The future action analyzed for cumulative effects is the Salmon Complex Fire Salvage. The model assumes no measureable impact to slope stability as the result of salvage logging so there is no additional landslide volume as a result of the future action (Table 8).

Eddy Gulch, Jessups Gulch and Shiltos Creek are under the threshold of concern (risk ratio greater than 1.0) for the GEO model. The watersheds are not likely to experience adverse impacts to the landslide rates as a result of the addition of the proposed and future actions. Olsen Creek is over the threshold of concern with a risk ratio of 1.73. The portion of the watershed on the north side of Salmon River (outside of project area) was impacted by the Salmon Complex Wildfire. The elevated CWE risk ratio does imply that the likelihood of landsliding during a 10 year storm event is highly likely. However, the cumulative risk of landsliding will remain in the high category because of the nature of the Elements at risk in the watershed.


6

Alternative 3 Direct Effects and Indirect Effects The footprint of Alternative 3 is smaller than Alternative 2 and therefore it has similar but smaller effect on landslide volume and landslide risk.

The landslide volume for alternative 3 is increased by less than 0.1% for Eddy Gulch, Shiltos Creek and Olsen Creek 7th field watershed. The landslide volume is by only 2% for Jessups Gulch. The modeling does not account for the project design features (Environmental Impact Statement, Chapter 2) prescribed to minimize the impacts of the project on Riparian Reserves.

Just as in Alternative 2, the percent of headwaters with harvest or burn and the CWE risk ratios are increased by the alternative but not enough to increase the overall landslide risk in any of the watersheds. The temporary roads on existing roadbeds are included in the current road density because they are currently in a drivable state and will require no earthwork to reopen for use. So the road density did not change at all by the alternative.

The overall landslide risk for the 7th field watersheds remains the same in Alternative 3 as Alternative 2.

Cumulative Effects The cumulative effects of Alternative 3 are the same as in Alternative 2 except the risk ratio for Jessups Gulch is 0.46 instead of 0.51 in alternative 2.

Summary of Effects The no action alternative does not effect the existing condition in the 7th field watersheds. The landslide volume remains at about 16000 yd3/decade, 18400 yd3/decade, 17200 yd3/decade, and 83200 yd3/decade for Eddy Gulch, Jessups Gulch, Shiltos Creek, and Olsen Creek respectively. Eddy Gulch has a moderate landslide risk. Jessups Gulch, Shiltos Creek and Olsen Creek have high landslide risks. Eddy Gulch has a risk ratio of 0.75, Jessups Gulch of 0.42, Shiltos Creek of 0.67 and Olsen Creek of 1.73.

Alternative 2 increases the landslide volume (over current) by less than 1% for Eddy Gulch, Shiltos Creek and Olsen Creek. Jessups Gulch has a landslide volume increase of about 8%. The landslide risk for the watersheds remains that same as for the no action alternative. The risk ratios also remain the same as for no action for the Eddy Gulch, Shiltos Creek and Olsen Creek. Jessups Gulch has a risk ratio of 0.51 under Alternative 2.

Alternative 3 increases the landslide volume (over current) by less than 0.1% for Eddy Gulch, Shiltos Creek and Olsen Creek. Jessups Gulch has a landslide volume increase of 2%. The landlside risk for the watersheds remains that same as for the no action. The risk ratios also remain the same as for no action for all the watersheds except Jessups Gulch is is 0.46 under Alternative 3.


7

Compliance with law, regulation, policy, and the Forest Plan (Heading 4) Existing mapping was field verified by the Forest Geologist and unstable lands were removed from treatment areas were slope stability was not benefited. The landsliding magnitude and risk were analyzed for all of the alternatives in the project. The risk associated with the direct/indirect and cumulative effects of the project have been minimized by project design features.


8

Geology Report Introduction The purpose of this report is to analyze the effects of the Jess project alternatives on landslide rates. Vegetation management can increase landslide rates by creating concentrations of surface water onto the hillslope, reduction of root support and canopy interception of rain and snow (Benda et al. 2005, Gutherie 2002, Slaymaker 2001 and Wolter et al. 2010).

The Forest Service Manual Chapter 2880 (Geologic Resources, Hazards and Services) requires the assessment of the risk of loss of life, property and natural resources from both naturally-occurring and management related landslides. The risk must be minimized or mitigated when possible. The Klamath National Forest Land and Resource Management Plan (LRMP) directs the interdisciplinary team (IDT) to manage vegetation on unstable lands to maintain or enhance slope stability (LRMP Standard and Guideline 2-1). Project-level review of the unstable lands is required to validate the current mapping (LRMP Standard and Guideline 2-2). Unstable lands are defined as active landslides, inner gorges, toe zones of dormant landslides and severely-weathered and dissected granitic lands. These features are considered Riparian Reserves (LRMP Standard and Guideline MA 10-2).

Proposed Actions and Alternatives Analyzed The Jess project proposes to manage fuel loadings, improve biological diversity by restoring ecological processes and to provide a range of ecosystem services within a 8,735 acre project area in the North Fork Salmon 5th field watershed. The proposed actions include timber harvest, roadside treatments, prescribed burning, mastication and meadow treatments. For a detail description of the proposed action analyzed in this report see Chapter 2 of the Jess project Environmental Impact Statement.

Methodology The Forest Geologist spent 18 field days validating existing geomorphic mapping and mapping previously unmapped unstable lands. During this time the Forest Geologist worked with the IDT to remove unstable lands from treatment areas where treatments were not focused on maintaining or enhancing slope stability.

Landsliding processes considered in this analysis are debris slides (avalanches), debris flows, translational/rotational slides and earthflows (USGS 2004). There are many factors influencing the stability, and therefore the landslide rate, of a hillslope including geomorphic landforms, vegetation condition, groundwater conditions and disturbances such as wildfire, timber harvest and road construction.

However, even the most unstable hillslopes need to experience a triggering event to produce landslides. Triggering events in the Klamath Mountains are often rain-on-snow events, but can be a convective storm during the summer or anything in between. Typically, landslide producing storms are a greater than a 10 year storm event. The landslide rate discussed in this report is that


9

related to storm events. Other landslide triggers are earthquakes and volcanic eruptions. While these are possible in the Klamath National Forest, they are not highly probable, so these triggers are not analyzed further in this report. Landslide rate is indirect effected by some forest management activities and is difficult to measure directly due to the complex and stochastic nature of these events. The analysis indicators analyzed are proxies for such processes.

Analysis Indicators This analysis uses three analysis indicators to indirectly capture the impacts to landslide rates in the project area.

1) Relative Landslide Volume. Landslide volume represents the magnitude of effects as a result of landsliding. The larger the volume the greater the effect to safety, property or natural resources. This indicator uses the empirical mathematical GEO Cumulative Watershed Effects (CWE) model to estimate the volume of sediment delivered to the mouth of a 7th field watershed due to all types of landsliding during a 10-year storm event. The coefficients in the mathematical equation were developed in the Salmon River basin and the model assumes the geomorphic landforms react identically regardless of elevation. The indirect effects will be analyzed using the landslide volume estimates attributed to the alternative relative to the existing condition volume estimates. In other words, how much does the estimated landslide volume increase or decrease as a result of the alternative? See Cumulative Watershed Effects: the Abridged Version (Bell 2012) and the CWE summary (Bell 2013) for a more detailed description of the model.

2) Landslide Risk. Landslide risk is the chance of effects of injury or loss as a measure of the probability and adverse consequences to safety, property or natural resources. (See Appendix A for detailed description of Landslide Risk Assessment). Landslide likelihood is determined by geomorphic landform, disturbance, landslide modeling, and road density. Debris slide and debris flow processes are most likely to be influenced by the loss of root strength and interception as a result of timber harvest and prescribed burning versus deep-seated landslides which are not as vulnerable to vegetation changes (Benda et al. 2005, Reid 2010 and Slaymaker 2001). Therefore, the focus of the landslide risk assessment is to analyze the indirect effects of the project alternatives on debris slide and debris flow processes.

The analysis uses existing geomorphic mapping, bedrock mapping and historical landslide information to determine the likelihood of landsliding. The consequences of a landslide are based on the impacts to Elements at Risk. The Elements at Risk for this analysis are dispersed campsites, ingress/egress, Sawyers Bar municipal water source (Jessups Gulch), fish habitat and water quality in a Key Watershed (North Fork Salmon River).

3) Cumulative Effects. The GEO CWE model risk ratio is used in the cumulative effects and is calculated as 2 times the “background” landslide volume over the current landslide volume. The threshold of concern for the risk ratio is 1.0. A risk ratio greater than or


10

equal to 1.0 is a yellow flag and calls for a closer look at mitigation opportunities. See Cumulative Watershed Effects: the Abridged Version (Bell 2012) and the CWE summary (Bell 2013) for a more detailed description of the model.

Spatial and Temporal Bounding of Analysis Area The spatial scale for analysis is the 7th field watershed scale for the direct/indirect effects and the cumulative effects. The models used for analysis are calibrated at a 7th field scale (Bell 2012). The temporal scale is 0-10 years for short-term and >10 years for long-term. Elevated landslide rates due to forest management have been shown to begin to decrease around 7-12 years after the disturbance in Northern California (Ziemer 1981).

Affected Environment The project area is within 4 7th field watersheds, Eddy Gulch, Jessups Gulch, Shiltos Creek and Olsen Creek.

Landslide Volume

Landslide volumes modeled under current conditions for the project area are summarized in Table 1. Ninety-eight, eighty-eight and eighty-five percent of the landslide volume from past management activities in Eddy Gulch, Jessups Gulch and Shiltos Creek are related to the existing road system respectively. The 2013 Salmon River Complex wildfire is the reason for almost seventy-five percent of the landslide volume modeled by the CWE GEO model.

Table 1: Landslide volumes estimated by CWE GEO model for the watershed in the project area under current conditions. 7th field Background

Landslide Volume (yd3/decade)

Current Landslide Volume as a result past management activities (yd3/decade)

Total Current Landslide Volume (yd3/decade)

Eddy Gulch 6419 9583 16002 Jessups Gulch 9795 8553 18348 Shiltos Creek 7346 9833 17179 Olsen Creek 18652 64588 83240

Landslide Risk

Landslide Likelihood

Under current conditions, a landslide event in Eddy Gulch and Jessups Gulch is likely (see appendix A) due to road densities in the watersheds. Shiltos Creek has a Highly Likely probability a landslide event due a high road density. A landslide event in Olsen Creek is highly likely because a high CWE GEO risk ratio. The ratio is elevated because of the 2013 Salmon Complex wildfire that burned north of the project area. (See Table 2)


11

Table 2: Landslide likelihood analysis for affected environment. 7th field % headwaters

harvest or burned with

high to moderate severity

CWE GEO Risk

Ratio

% unstable lands

Road Density (mi/mi2)

Likelihood of landsliding

Eddy Gulch 0% 0.75 16.4% 2.1 Likely Jessups Gulch 0% 0.42 15.6% 2.3 Likely Shiltos Creek 4.3% 0.67 21.6% 3.1 Highly Likely Olsen Creek 22.6% 1.73 31.7% 1.6 Highly Likely

Landslide Consequence Eddy Gulch has two Elements at Risk. The first being ingress/egress along the Eddy Gulch County road and the second ingress/egress on Forest Road 39N27. The county road is about 150 feet above the stream and is not likely to be affected by a debris flow in Eddy Gulch. The crossing near the top of the county segment is a bridge designed to pass high flows and debris flows. A landslide event will result in a nuisance consequence on the county road. Crossings along 39N27 could be impacted by debris flows resulting in a moderate consequence.

Jessups Gulch has three Elements at Risk. The first being dispersed campsites 54D014 and 54D013. The second being ingress/egress on Forest Road 39N27 and the third being the municipal water supply for Sawyers Bar, California. The dispersed campsites are offset from the stream channels and would not likely be affected by a debris flow. Ingress/Egress on 39N27 would be compromised if a debris flow would occur leading to a moderate consequence. A debris flow in the main stem of Jessups Gulch would impact water quality by increasing sediment and temperature. The increase in sediment would last for about 3-5 years as the winter flows flush the system. Temperature would be increased for 5-10 years until riparian vegetation is re-established along the banks for the stream. The water treatment plant would be impacted because of the sediment increase and could be physically damaged by the actual debris flow. The consequences of a landslide event would be a major consequence.

The Elements at Risk in Shiltos Creek is the ingress/egress on 39N27 and the dispersed campsite 54D017. The dispersed campsite is offset from the stream channels and would not likely be affected by a debris flow. Ingress/Egress on 39N27 would be compromised if a debris flow would occur leading to a moderate consequence. In Olsen Creek ingress/egress on Forest Road 39N27 would be compromised if a debris flow event would occur leading to a moderate consequence.


12

All of the 7th field watersheds analyzed are tributaries to the North Fork of the Salmon River which provides coho and chinook fish habitat and are within a Key Watershed, which are both Elements at Risk. The tributaries themselves do not have coho or chinook habitat. The effects of a debris flow that reaches the North Fork of the Salmon river would be an introduction of sediment and the loss of shade on cold water tributaries. This would negatively impact both fish habitat and water quality. Debris flows occurred in Olsen Creek during the 1964 flood event on the north side of the river (not within the project area) the other watersheds do not show evidence of experiencing recent debris flows (< 80 years). So the impacts to fisheries and water quality are likely to be limited in extent and the consequence would be moderate.

Table 3: Overall landslide risk assessment for affected environment under current conditions for 7th field watersheds.

7th field Likelihood Consequence Landslide Risk

Eddy Gulch Likely Moderate Moderate

Jessups Gulch Likely Major High

Shiltos Creek Highly Likely Moderate High

Olsen Creek Highly Likely Moderate High

There is currently a moderate landslide risk to ingress/egress on 39N27 and the County road, as well as for fish habitat and water quality (other than for potable water), for Eddy Gulch Creek 7th field watershed (see Table 3).

There is a high landslide risk for the municipal water supply and ingress/egress for Jessups Gulch. But only a moderate landslide risk to fish habitat and water quality (other than for potable water) in Jessups Gulch.

There is a high landslide risk for ingress/egress, fish habitat and water quality (other than for potable water) in Shiltos and Olsen Creek.

Cumulative Watershed Effects Modeling

The CWE GEO model incorporates all the past actions into the current landslide volume and risk ratio (Table 4). Eddy Gulch, Jessups Gulch and Shiltos Creek are all under the threshold of concern. Olsen Creek has an elevated risk ratio due to the effects of the 2013 Salmon Complex wildfire.


13

Table 4: Summary of CWE GEO modeling for current conditions in the affected environment. HUC 14 HUC 14 Name Background

(yd3/decade) Current (yd3/decade)

Roads (yd3/decade)

Current total GEO

Current Risk Ratio

18010210020703 Eddy Gulch 6419.6 139.6 9444.1 16003 0.75 18010210020704 Jessups Gulch-North

Fork Salmon River 9795.0 943.6 7339.1 18077 0.42

18010210020706 Shiltos Creek-North Fork Salmon River

7346.6 1439.1 8393.8 17179 0.67

18010210020801 Olsen Creek-North Fork Salmon River

18652.1 51131.2 13457.4 83240 1.73

Environmental Consequences Alternative 1 Direct Effects and Indirect Effects Under this alternative no management action will be taken. There are no direct or indirect effects to landslide rates.

Cumulative Effects There are no direct or indirect effects for this alternative and therefore no cumulative effects.

Alternative 2 Direct and Indirect Effects The landslide volume for alternative 2 is increased by less than 1% for Eddy Gulch, Shiltos Creek and Olsen Creek 7th field watershed. The landslide volume is increased by almost 8% for Jessups Gulch (see Table 5). The modeling does not account for the project design features (Environmental Impact Statement, Chapter 2) prescribed to minimize the impacts of the project on Riparian Reserves. The treatments in inner gorges are limited by the commercial harvest and equipment exclusion zones. There is also a decrease in the road related landsliding volume as a result of the hydrologic stabilization of the temporary roads on existing roadbeds (See Table 8).

Table 5: Landslide volume as estimated by the CWE GEO model for alternative 2. 7th field Total Current


Landslide volume increase from Alternative

Percent increase in Landslide Volume by Alternative

Eddy Gulch 16002 102 0.6% Jessups Gulch 18348 1427 7.8% Shiltos Creek 17179 71 0.4% Olsen Creek 83240 18 0.02% The percent of headwaters with harvest or burn and the CWE risk ratios are increased by the alternative (Table 6) but not enough to increase the overall landslide risk in any of the watersheds (Table 7). The temporary roads on existing roadbeds are included in the current road


14

density because they are currently in a drivable state and will require no earthwork to reopen for use. So the road density did not change at all by the alternative.

Jessups Gulch, Shiltos Creek and Olsen Creek have high landslide risk. According to the risk matrix (Table 12 in Appendix A) projects mitigations should be prescribed to mitigate impacts. There are 45 project design features prescribed in Chapter 2 of the Environmental Impact Statement (Watershed-1 through Watershed-45) that are intended to minimize impacts to watershed health and landslide rates.

Table 6: Landslide likelihood analysis for alternative 2. 7th field % headwaters

harvest or burned with

high to moderate severity

CWE GEO Risk

Ratio

% unstable lands



Eddy Gulch 0.10% 0.75 16.4% 2.1 Likely Jessups Gulch 22.3% 0.51 15.6% 2.3 Likely Shiltos Creek 9.5% 0.67 21.6% 3.1 Highly Likely Olsen Creek 23.7% 1.73 31.7% 1.6 Highly Likely Table 7: Overall landslide risk assessment for Alternative 2.






Cumulative Effects The current CWE GEO values in Table 8 include the past actions that have occurred in the 7th field watersheds for the past 50 years and the current actions. The recent past and current actions include the North Fork Roads Stormproofing project, Eddy Late Successional Reserve Restoration project, Glassups project and the road work done under the Burned Area Emergency Response. The future action analyzed for cumulative effects is the Salmon Complex Fire Salvage. The model assumes no measureable impact to slope stability as the result of salvage logging so there is no additional landslide volume as a result of the future action (Table 8).

Eddy Gulch, Jessups Gulch and Shiltos Creek are under the threshold of concern (risk ratio greater than 1.0) for the GEO model. The watersheds are not likely to experience adverse


15

impacts to the landslide rates as a result of the addition of the proposed and future actions. Olsen Creek is over the threshold of concern. The portion of the watershed on the north side of Salmon River (outside of project area) was impacted by the Salmon Complex Wildfire. The elevated CWE risk ratio does imply that the likelihood of landsliding during a 10 year storm event is highly likely. However, the risk of landsliding will remain in the high category because of the nature of the Elements at risk in the watershed. Table 8: Cumulative Watershed Effects GEO model results for Alternative 2. 7th field watershed

7th field name Current (yd3/ decade)

Alt. 2 (yd3/ decade)

Future (yd3/ decade)

Temp Rd on existing roadbed

Saved by temp road decom

Alt 2. total GEO CWE (yd3/ decade)

Alt. 2 Risk Ratio

18010210020703

Eddy Gulch 9584 101 0

16105

0.75

18010210020704

Jessups Gulch-North Fork Salmon River 8283 1427 0 902 -631 19775

0.51

18010210020706

Shiltos Creek-North Fork Salmon River 9833 71 0

17251

0.67

18010210020801

Olsen Creek-North Fork Salmon River 64589 18 0

83258

1.73

Alternative 3 Direct and Indirect Effects The footprint of Alternative 3 is much smaller than Alternative 2 and therefore it has fewer effects on landslide volume and landslide risk.

The landslide volume for alternative 3 is increased by less than 0.1% for Eddy Gulch, Shiltos Creek and Olsen Creek 7th field watershed. The landslide volume is by only 2% for Jessups Gulch (see Table 9). The modeling does not account for the project design features (Environmental Impact Statement, Chapter 2) prescribed to minimize the impacts of the project on Riparian Reserves. The treatments in inner gorges are limited by the commercial harvest and equipment exclusion zones. There is also a decrease in the road related landsliding volume as a result of the hydrologic stabilization of the temporary roads on existing roadbeds (See Table 12).

Table 9: Landslide volume as estimated by the CWE GEO model for alternative 3. 7th field Total Current


Landslide volume increase from Alternative

Percent increase in Landslide Volume by Alternative

Eddy Gulch 16002 22 0.1% Jessups Gulch 18348 354 2.0% Shiltos Creek 17179 1 0% Olsen Creek 83240 18 0.02%


16

Just as in Alternative 2, the percent of headwaters with harvest or burn and the CWE risk ratios are increased by the alternative (Table 10) but not enough to increase the overall landslide risk in any of the watersheds (Table 11). The temporary roads on existing roadbeds are included in the current road density because they are currently in a drivable state and will require no earthwork to reopen for use. So the road density did not change at all by the alternative.

Jessups Gulch, Shiltos Creek and Olsen Creek have high landslide risk. According to the risk matrix (Table 12 in Appendix A) projects mitigations should be prescribed to mitigate impacts. There are 45 project design features prescribed in Chapter 2 of the Environmental Impact Statement (Watershed-1 through Watershed-45) that are intended to minimize impacts to watershed health and landslide rates.

Table 10: Landslide likelihood analysis for alternative 3.

7th field % headwaters harvest or

burned with high to

moderate severity

CWE GEO Risk

Ratio

% unstable lands



Eddy Gulch 0% 0.75 16.4% 2.1 Likely

Jessups Gulch 5.9% 0.46 15.6% 2.3 Likely

Shiltos Creek 4.3% 0.67 21.6% 3.1 Highly Likely

Olsen Creek 22.6% 1.73 31.7% 1.6 Highly Likely Table 11: Overall landslide risk assessment for alternative 3.






Cumulative Effects

The current CWE GEO values in Table 12 include the past actions that have occurred in the 7th field watersheds for the past 50 years and the current actions. The recent past and current actions include the North Fork Roads Stormproofing project, Eddy Late Successional Reserve


17

Restoration project, Glassups project and the road work done under the Burned Area Emergency Response. The future action analyzed for cumulative effects is the Salmon Complex Fire Salvage. The model assumes no measureable impact to slope stability as the result of salvage logging so there is no additional landslide volume as a result of the future action (Table 12).

Eddy Gulch, Jessups Gulch and Shiltos Creek are under the threshold of concern (risk ratio greater than 1.0) for the GEO model. The watersheds are not likely to experience adverse impacts to the landslide rates as a result of the addition of the proposed and future actions. Olsen Creek is over the threshold of concern. The portion of the watershed on the north side of Salmon River (outside of project area) was impacted by the Salmon Complex Wildfire. The elevated CWE risk ratio does imply that the likelihood of landsliding during a 10 year storm event is highly likely. However, the risk of landsliding will remain in the high category because of the nature of the Elements at risk in the watershed. Table 12: Cumulative Watershed Effects GEO model results for Alternative 3. 7th field watershed

7th field name Current (yd3/decade)

Alt. 2 (yd3/decade)

Future (yd3/decade)

Temp Rd on existing roadbed

Saved by temp road decom

Alt 2. total GEO CWE (yd3/decade)

Alt. 2 Risk Ratio

18010210020703

Eddy Gulch 9584 22 0 0 0 16018 0.75

18010210020704

Jessups Gulch-North Fork Salmon River 8282 354 0 902 -631 18593 0.46

18010210020706

Shiltos Creek-North Fork Salmon River 9832 1 0 0 0 17176 0.67

18010210020801

Olsen Creek-North Fork Salmon River 64589 18 0 0 0 83246 1.73

Compliance with law, regulation, policy, and the Forest Plan Existing mapping was field verified by the Forest Geologist and unstable lands were removed from treatment areas were slope stability was not benefited. The landsliding magnitude and risk were analyzed for all of the alternatives in the project. The risk associated with the direct/indirect and cumulative effects of the project have been minimized by project design features.


18

Literature Cited

Benda, L., Hassan, M., Church, M., May, C. 2005. Geomoprhology of Steepland Headwaters: The Transition from Hillslopes to Channels. Journal of American Water Resources Association.

Gutherie, R. 2002. The Effects of Logging on Frequency and Distribution of Landslides in Three Watersheds on Vancouver Island, British Columbia. Geomorphology.

Reid, L. 2010. Cumulative Watershed Effects of Fuel Management in the Western United States: Chapter 6 – Cumulative Effects of Fuel Treatments on Channel Erosion and Mass Wasting. Rocky Mountain Research Station, General Technical Report. RMRS-GTR-231.

Slaymaker, O. 2001. Geomorphic Impacts of Timber Harvest. Chinese Science Bulletin.

USFS. 2008. Forest Service Manual 2880 – Geologic Resources, Hazards and Services.

USFS. 2012. Cumulative Watershed Effects Modeling: The Abridged Version. Prepared by Angie Bell, Forest Geologist, for the Klamath National Forest.

USGS) U.S. Geological Survey. 2004. Landslide Types and Processes, Fact Sheet 2004-3072. Retrieved on 19 August 2013 from http://pubs.usgs.gov/fs/2004/3072/

Wolter, A., Ward, B., Millard, T. 2010. Instability in Eight Sub-basins of the Chilliwack River Valley, British Columbia, Canada: A Comparison of Natural and Logging-related Landslides. Geomorphology.

Ziemer, R. 1981. The Role of Vegetation in the Stability of Forested Slopes. Pacific Southwest Research Station. Arcata, CA.

http://pubs.usgs.gov/fs/2004/3072/


19

Appendix A – Landslide Risk Assessment Landslide risk compares the likelihood of a landslide event and the consequences of the event.

Landsliding Likelihood

Landslide likelihood is determined by geomorphic landform, disturbance, vegetation condition, bedrock type, and groundwater conditions. The analysis uses existing geomorphic mapping, bedrock mapping and historical landslide information to determine the likelihood of landsliding. A majority of the west side of the Forest is relatively unstable so the likelihood of having small localized landslides in any given 7th field watershed during any storm is highly probable. This analysis is focused on determining the likelihood of a landslide event. A landslide event is defined for this analysis as large-scale, extensive episode resulting in several landslides that could interrupt ingress/egress, fluvial processes on 3-5th order streams or damage major infrastructure across a 7th field watershed.

The likelihood of a landsliding event was analyzed at the 7th field watershed scale using a combination of the percent of headwaters (0th to 1st order streams on upper 1/3 of slope) harvested or burned within the last 10 years, CWE GEO risk ratio, percent of unstable lands and the road density.

The likelihood categories are summarized below:

1) Almost Certain – a landsliding event is expected to occur even under an average storm event (2 year storm event). A watershed in this category meets at least two of the following criteria: 1) Greater than 25% of the headwaters that have had high to moderate severity harvest or burned in the past 10 years, 2) CWE GEO risk ratio greater than 1.2, 3) greater than 30% of area designated as unstable lands (per definition in Forest Plan), or 4) a road density greater than to 4.0 mi/mi2.

2) Highly Likely – A landsliding event will probably occur under an average storm event. A watershed in this category meets at least one of the following criteria: 1) Greater than 25% of the headwaters have had high to moderate severity harvest or burned in the past 10 years, 2) CWE GEO risk ratio is greater than 0.95, 3) Greater than 25% of the area is designated as unstable lands, or 4) a road density greater than 3.5 mi/mi2.

3) Likely – A landsliding event is likely to occur under a 10-20 year storm event. A watershed in this category meets at least one of the following criteria: 1) Between 10-25% of the headwaters have had high to moderate severity harvest or burned in the past 10 years, 2) CWE GEO risk ratio is between 0.75 and 0.95, 3) Between 10-25% of the area is designated as unstable lands, or 4) a road density between 1.5 and 3.5 mi/mi2.


20

4) Unlikely – Landsliding might occur under a 20-99 year storm event. A watershed in this category meets if it is on the west side of the Forest and does not meet the criteria in above categories.

5) Rare – Landsliding is conceivable but only under a ≥ 100 year storm event. A watershed meets this category if it is on the east side of the Forest (with occasional exceptions).

Consequence Categories The consequences of a landslide are based on the impacts to Elements at Risk. The Elements at Risk for this analysis are human safety, infrastructure, property, recreation/visitor use and environmental resources. The consequences categories are summarized below:

a) Catastrophic Consequences– In this category landsliding in the analysis area has a reasonable probability of directly causing injury or the loss of a human life. The presents of occupied structures (homes, businesses, work areas), campgrounds, or heavily used road would meet the criteria for this category.

b) Major Consequences – In this category there is a reasonable probability that essential infrastructure such as National Forest System roads, power lines, pipelines, municipal water sources, and railroads may be rendered inoperative. The Major Damage category applies to landsliding that has a reasonable probability of leading to the complete loss of anadromous fisheries habitat in the analysis area. This category also applies when landsliding has a reasonable probability of aggrading or degrading the stream channel or reducing shade and riparian vegetation over a large portion of late flowing intermittent or perennial streams in the analysis area.

c) Moderate Consequences – In this category there is a reasonable probability of that non-essential infrastructure and property such campgrounds (unoccupied), trailheads, day use areas and system trails will be rendered inoperable. Landsliding debris blocking major ingress/egress roadways. The Moderate Damage category applies to landsliding that has a reasonable probability of leading to the partial loss of anadromous fisheries habitat in the analysis area. This category also applies when landsliding has a reasonable probability of aggrading or degrading the stream channel or reducing shade and riparian vegetation over a small portion of late flowing intermittent and perennial streams in the analysis area.

d) Minor Consequences – in this category there is a reasonable probability of damage to infrastructure that does not render it inoperable but makes its operation unsafe or inconvenient (e.g. There is debris partially blocking a two lane road). The Minor Damage category applies to landsliding that has a reasonable probability of reducing shade at the a local scale or blocking the stream for the short term (<6 months).


21

e) Nuisance Consequences – In this category there is not a reasonable probability of damage infrastructure, anadromous fisheries habitat or stream shade.

Landslide Risk Matrix The landslide risk matrix (Table 12) is the cross-walk between the likelihood and consequences and the implications for Forest management. Once the likelihood and consequences have been determined using the criteria above the risk matrix is used to determine the risk category that fits that situation. For instance, you may have an area that is likely to experience landsliding during a 10-year storm event and has essential infrastructure vulnerable to landsliding. In this case the landslide risk is High. This risk has implications for Forest management which is described in the section below.

22

Table 13: the landslide risk matrix shows how likelihood is compared with consequence to determine the landslide risk. The likelihood is based on GEO-CWE results and landslide history and consequences based on the Elements at Risk.

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. Further investigation will be needed to determine the extent of mitigation needed prior to the implementation of Forest management activities.

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.

23

Literature Reviewed in Assessment Development

Lee, E., and Jones, K. 2004. Landslide Risk Assessment. Thomas Telford Publishing, London, England.

Australian Geomechanics Society. 2007. Practice Note Guidelines for Landslide Risk Management 2007. Journal and News of the Australian Geomechanics Society. Vol. 42, issue 1.

Dai, F., Lee, C., Ngai, Y. 2002. Landslide Risk Assessment and Management: an Overview. Engineering Geology. Vol 64.

Wise, M., Moore, G., and VanDine, D. (eds.). 2004. Landslide Risk Case Studies in Forest Development Planning and Operations. Land Management Handbook 56, British Columbia Ministry of Forestry Publication.

24

Appendix B: Unstable Lands and Headwaters Analyzed

Map 1: Unstable lands and headwaters analyzed in Environmental Effects section of this report. This is an embedded .pdf. Click on image to open in .pdf reader to view in higher resolution.

Geology Report -...

Documents

Transcript of Geology Report -...