Whatcom County Flood Control Zone District Jones Creek Debris Flow Study Final Report March 2004 Whatcom County Flood Control Zone District Jones Creek Debris Flow Study Final Report March 2004 KWL File No. 2039.002 JONES CREEK DEBRIS FLOW STUDY FINAL REPORT MARCH 2004 WHATCOM COUNTY FLOOD CONTROL ZONE DISTRICT STATEMENT OF LIMITATIONS This document has been prepared by Kerr Wood Leidal Associates Limited (KWL) for the exclusive use and benefit of Whatcom County Public Works Department. No other party is entitled to rely on any of the conclusions, data, opinions, or any other information contained in this document. This document represents KWL’s best professional judgement based on the information available at the time of its completion and as appropriate for the project scope of work. Services performed in developing the content of this document have been conducted in a manner consistent with that level and skill ordinarily exercised by members of the engineering profession currently practising under similar conditions. No warranty, expressed or implied, is made. KERR WOOD LEIDAL ASSOCIATES LTD. Consulting Engineers 2039.001 JONES CREEK DEBRIS FLOW STUDY FINAL REPORT WHATCOM COUNTY FLOOD CONTROL ZONE DISTRICT MARCH 2004 CONTENTS EXECUTIVE SUMMARY .......................................................................................i 1. INTRODUCTION.................................................................................... 1-1 1.1 BACKGROUND............................................................................................................... 1-1 1.2 CREEK HAZARDS .......................................................................................................... 1-2 1.3 WORK PROGRAM .......................................................................................................... 1-3 1.4 PROJECT TEAM............................................................................................................. 1-5 2. JONES CREEK BACKGROUND........................................................... 2-1 2.1 JONES CREEK FAN........................................................................................................ 2-1 2.2 1983 DEBRIS FLOW ...................................................................................................... 2-2 2.3 OTHER CREEK EVENTS.................................................................................................. 2-6 2.4 REGULATION OF FAN HAZARDS...................................................................................... 2-6 2.5 JONES CREEK ALLUVIAL FAN ASSESSMENT .................................................................... 2-9 2.6 ACME WATERSHED ANALYSIS (1999)........................................................................... 2-12 3. DEBRIS FLOW RISK ANALYSIS.......................................................... 3-1 3.1 INTRODUCTION.............................................................................................................. 3-1 3.2 DEBRIS FLOW AND FLOOD HAZARDS .............................................................................. 3-1 3.3 DEBRIS FLOW MODELLING ............................................................................................. 3-5 3.4 POTENTIAL CONSEQUENCE............................................................................................ 3-8 3.5 POTENTIAL DEBRIS FLOW RISKS .................................................................................... 3-9 4. RISK MITIGATION ALTERNATIVES .................................................... 4-1 4.1 INTRODUCTION.............................................................................................................. 4-1 4.2 LAND USE PLANNING AND DEVELOPMENT ....................................................................... 4-2 4.3 WARNING SYSTEMS....................................................................................................... 4-4 4.4 WATERSHED MANAGEMENT ACTIONS.............................................................................. 4-6 4.5 DEBRIS FLOW MITIGATION STRUCTURES ......................................................................... 4-7 4.6 SUMMARY OF ALTERNATIVE DEBRIS FLOW MITIGATION MEASURES ................................. 4-10 4.7 CREEK MANAGEMENT MEASURES................................................................................. 4-12 4.8 PREFERRED RISK MITIGATION ALTERNATIVES................................................................ 4-13 5. SUMMARY AND RECOMMENDATIONS.............................................. 5-1 5.1 SUMMARY..................................................................................................................... 5-1 5.2 RECOMMENDATIONS...................................................................................................... 5-3 5.3 REPORT SUBMISSION..................................................................................................... 5-5 BIBLIOGRAPHY KERR WOOD LEIDAL ASSOCIATES LTD. Consulting Engineers 2039.002 JONES CREEK DEBRIS FLOW STUDY FINAL REPORT WHATCOM COUNTY FLOOD CONTROL ZONE DISTRICT MARCH 2004 FIGURES 1-1 Location Map 1-2 Overview Map of Jones Creek Watershed 1-3 Jones Creek Fan 2-1 Geomorphic Map of Lower Watershed 2-2 2001 Aerial Photograph of Jones Creek Fan 2-3 Jones Creek Watershed Following 1983 Debris Flow 2-4 Fan Hazard Zones of Raines et al. (1996) 3-1 Jones Creek Debris Flow Modelling Results for the Design Event 3-2 Jones Creek Debris Flow Hazard Zones 4-1 Concept Plan for Debris basin and Debris Barrier 4-2 Concept Plan for Deflection Berm 4-3 Possible Channel Realignment of Jones Creek TABLES 1-1 Work Program for Jones Creek 2-1 Hazard Zones of Raines et al. (1996) 2-2 Recommended Allowable Uses in Hazard Zones – Raines et al. (1996) 4-1 Land Use Regulations for Existing and New Developments in Switzerland 4-2 Debris Flow Mitigation Alternatives at Jones Creek APPENDICES A Background Information on Debris Floods and Debris Flows B Photographs C Watershed Description D Mass Movement Processes E Hydrologic Analysis F Debris Flow Probability and Magnitude G Fan Trench Stratigraphy KERR WOOD LEIDAL ASSOCIATES LTD. Consulting Engineers 2039.002 JONES CREEK DEBRIS FLOW STUDY FINAL REPORT WHATCOM COUNTY FLOOD CONTROL ZONE DISTRICT MARCH 2004 CONTENTS EXECUTIVE SUMMARY............................................................................................... i 1. INTRODUCTION.............................................................................................1-1 1.1 BACKGROUND.........................................................................................................1-1 1.2 CREEK HAZARDS.....................................................................................................1-2 1.3 WORK PROGRAM ....................................................................................................1-3 1.4 PROJECT TEAM .......................................................................................................1-5 2. JONES CREEK BACKGROUND.................................................................2-1 2.1 JONES CREEK FAN ..................................................................................................2-1 2.2 1983 DEBRIS FLOW.................................................................................................2-2 2.3 OTHER CREEK EVENTS.............................................................................................2-6 2.4 REGULATION OF FAN HAZARDS..................................................................................2-6 2.5 JONES CREEK ALLUVIAL FAN ASSESSMENT.................................................................2-9 2.6 ACME WATERSHED ANALYSIS (1999) ....................................................................... 2-12 3. DEBRIS FLOW RISK ANALYSIS................................................................3-1 3.1 INTRODUCTION........................................................................................................3-1 3.2 DEBRIS FLOW AND FLOOD HAZARDS ..........................................................................3-1 3.3 DEBRIS FLOW MODELLING ........................................................................................3-5 3.4 POTENTIAL CONSEQUENCE .......................................................................................3-8 3.5 POTENTIAL DEBRIS FLOW RISKS ................................................................................3-9 4. RISK MITIGATION ALTERNATIVES ..........................................................4-1 4.1 INTRODUCTION........................................................................................................4-1 4.2 LAND USE PLANNING AND DEVELOPMENT....................................................................4-2 4.3 WARNING SYSTEMS .................................................................................................4-4 4.4 WATERSHED MANAGEMENT ACTIONS .........................................................................4-6 4.5 DEBRIS FLOW MITIGATION STRUCTURES .....................................................................4-7 4.6 SUMMARY OF ALTERNATIVE DEBRIS FLOW MITIGATION MEASURES................................ 4-10 4.7 CREEK MANAGEMENT MEASURES ............................................................................ 4-12 4.8 PREFERRED RISK MITIGATION ALTERNATIVES ............................................................ 4-14 5. SUMMARY AND RECOMMENDATIONS...................................................5-1