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  • CAYOOSH CREEK WATERSHED

    Risk Assessment

    Prepared for: Ainsworth Engineered Canada LP

    Lillooet Division

    Submitted by: Integrated ProAction Corp.

    1425 Hugh Allan Drive, Kamloops, BC V1S 1J3 Phone: 250-828-7977 Fax: 250-828-2183

    Website: www.intpac.ca

    March 30, 2007

  • EXECUTIVE SUMMARY This Watershed Risk Assessment is a Forest Investment Account (FIA) funded project to identify and complete a risk assessment for the non-status roads in the Cayoosh Creek Watershed. Ainsworth Engineered Canada LP is the lead licensee and responsible for the management of FIA funding in the Lillooet Timber Supply Area (TSA). This project followed the standards outlined in the FIA Activity Standards for Road Deactivation, Landslide and Gully Rehabilitation Projects Document (Version 5 2003/2004). The risk assessment was carried out in conjunction with an Access Management Plan for the Cayoosh Creek Watershed. The objective of this project is to complete a risk assessment for each non-status road within the project area. The results from this project will be used in the Access Management Plan to determine which non-status roads should be deactivated and which should receive environmental maintenance. The Cayoosh Creek watershed is located southwest of the district of Lillooet and covers an area of approximately 1165.3 km2. The project area includes: Cayoosh Creek, Enterprise Creek, Downton Creek, Boulder Creek, Gott Creek, Van Horlick Creek, Casper Creek, Blowdown Creek, Texas Creek, and Seton ridge. A partial risk analysis was completed for the non-status roads that were identified within the project area. Partial risk analysis involves determining the likelihood of occurrence of a landslide and that landslide being a hazard to and directly or indirectly reaching or otherwise affecting a specific value at risk. Risk, as it pertains to this project, relates to the likelihood of landslides resulting from forest development (roads) and surface erosion and sediment delivery to streams and was determined to be the product of the risk multiplied by the consequence. Of the 225 non-status roads or road sections identified in the project 13 are classified as very high risk, 29 are classified as high risk and the remaining 183 were classified as either moderate or low risk. This report provides a qualitative evaluation of potential landslide and erosion hazards associated with non-status roads in the project area, an estimate of the downslope/downstream landslide consequences, recommendations, and a prioritized list for future field assessments and remedial work. Field assessments were not possible due to the timing of the project. A field assessment of all the roads is required in snow-free conditions to confirm the risk ratings determined in this report.

  • Table of Contents

    1. INTRODUCTION ...................................................................................................... 1 1.1. PROJECT OVERVIEW ............................................................................................ 1 1.2. TERMS OF REFERENCE ......................................................................................... 1

    2. STUDY AREA DESCRIPTION ................................................................................ 1 2.1. CHARACTERISTICS OF THE CAYOOSH CREEK WATERSHED.................................. 1 2.2. NON-STATUS ROADS WITHIN THE CAYOOSH CREEK WATERSHED ...................... 1 2.3. NON-STATUS ROAD LINKAGES TO THE PUBLIC ROAD SYSTEM .......................... 2

    3. WATERSHED RISK ASSESSMENT ....................................................................... 2 3.1. OBJECTIVES OF THE WATERSHED RISK ASSESSMENT .......................................... 2 3.2. RISK ASSESSMENT PROCEDURE ........................................................................... 2 3.3. RISK RATING DESCRIPTION ................................................................................. 3

    3.3.1. Low Risk Roads........................................................................................... 3 3.3.2. Moderate Risk Roads .................................................................................. 4 3.3.3. High Risk Roads.......................................................................................... 4 3.3.4. Very High Risk Roads ................................................................................. 4

    3.4. RISK RATING RESULTS ........................................................................................ 4 4. CONCLUSION........................................................................................................... 5 5. LIMITATIONS........................................................................................................... 7 6. REFERENCES ........................................................................................................... 8

    List of Tables

    Table 1: Risk Rating Matrix ............................................................................................... 3 Table 2: Number of roads within each risk rating in the Cayoosh Creek Watershed......... 5 Table 3: Road Assessment/Work Priority........................................................................... 5

    List of Appendices

    Appendix 1: General Location Map Appendix 2: Description of Road Risk Rating Criteria Appendix 3: Description of Road Consequence Rating Appendix 4: Risk Rating Summary Appendix 5: Risk Assessment Map

  • Cayoosh Creek Watershed 1 Watershed Risk Assessment

    1. INTRODUCTION 1.1. PROJECT OVERVIEW

    This Watershed Risk Assessment (WRA) is funded by the Forest Investment Account (FIA) Land-base Program, Restoration & Rehabilitation Component, Terrestrial Activity Area. Ainsworth Engineered Canada LP is the lead Licensee and responsible for the management of FIA funding in the Lillooet Timber Supply Area (TSA). The objective of this project is to complete a risk assessment for each non-status road within the Cayoosh Creek watershed in the Lillooet TSA which includes: Cayoosh Creek, Enterprise Creek, Downton Creek, Boulder Creek, Gott Creek, Van Horlick Creek, Casper Creek, Blowdown Creek, Texas Creek, and Seton Ridge (see Appendix 1 for an overview map of the project area). The results of this risk assessment will be used to identify and prioritize the non-status roads that should be deactivated or that should receive environmental maintenance through the FIA program.

    1.2. TERMS OF REFERENCE The Watershed Risk Assessment was completed within the time frame and budget submitted to Ainsworth Engineered Canada LP by Integrated ProAction Corp. Furthermore, the WRA was drafted in accordance with both the 2003/2004 FIA standards for road deactivation, landslide and gully rehabilitation projects and the 2003/2004 FIA standards for environmental maintenance projects on non-status forest roads.

    2. STUDY AREA DESCRIPTION 2.1. CHARACTERISTICS OF THE CAYOOSH CREEK WATERSHED

    The Cayoosh Creek Watershed is located east of the Coast Mountains and west of the Thompson-Okanagan Plateau, within the Fraser Plateau, Eastern South Coast Mountains, and Northern Thompson Plateau hydrologic zones. The watershed is located southwest of the district of Lillooet (see Appendix 1) and covers an area of approximately 1165.3 km2, 97.1 % of which is crown land. Private land accounts for 2%, (23.3 km2), and Indian Reserves account for the remaining 0.9% (10.5 km2) of the land within the project area. The elevation within the watershed ranges from approximately 200m at the boundary on the Fraser River to a maximum of approximately 2880m at the mountain peaks around Enterprise, Copper, and Downton Creeks. The regions streamflow is generated from lakes, overland flow (runoff) and snowmelt. The Cayoosh Creek watershed has eight Biogeoclimatic Ecosystem Classification (BEC) zones within its boundary: Coastal Western Hemlock (CWH), Mountain Hemlock (MH), Ponderosa Pine (PP), Interior Douglas Fir (IDF), Montane Spruce (MS), Engelmann Spruce-Subalpine Fir (ESSF), Interior Mountain-heather Alpine (IMA), and Coastal Mountain-heather Alpine (CMA).

    2.2. NON-STATUS ROADS WITHIN THE CAYOOSH CREEK WATERSHED Several sources were used to determine the status of roads within the project area including consolidated FDP data, Land and Resource Data Warehouse (LRDW) road data, road data from Ainsworth, and Terrain Resource Inventory Mapping (TRIM). Of the

  • Cayoosh Creek Watershed 2 Watershed Risk Assessment

    roads identified in the watershed, approximately 216 are currently not under permit and are classified as non-status roads.

    2.3. NON-STATUS ROAD LINKAGES TO THE PUBLIC ROAD SYSTEM All of the roads within the project area directly or indirectly link to Highway 99, also known as the Duffey Lake road.

    3. WATERSHED RISK ASSESSMENT 3.1. OBJECTIVES OF THE WATERSHED RISK ASSESSMENT

    The objective of this project is to complete a risk assessment for each non-status road within the project area. Risk, as it pertains to this project, relates to the likelihood of landslides resulting from forest development (roads) and surface erosion and sediment delivery to streams.

    3.2. RISK ASSESSMENT PROCEDURE A partial risk analysis was completed for the non-status roads that were identified within the project area. Partial risk analysis involves determining the likelihood of occurrence of a landslide and that landslide being a hazard to and directly or indirectly reaching or otherwise affecting a specific value at risk. Partial risk analysis is not a measure of the expected degree of damage to a specific value (MoF 2003b).

    Alternatively, specific risk analysis or total risk analysis may be more appropriate to conduct if the vulnerabi

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