Utility Guidance for Mitigating Catastrophic Vegetation Change in Watersheds Subject Area: Water Resources and Environmental Sustainability Utility Guidance for Mitigating Catastrophic Vegetation Change in Watersheds ©2009 Water Research Foundation. ALL RIGHTS RESERVED About the Water Research Foundation The Water Research Foundation (formerly Awwa Research Foundation or AwwaRF) is a member-supported, international, 501(c)3 nonprofit organization that sponsors research to enable water utilities, public health agencies, and other professionals to provide safe and affordable drinking water to consumers. The Foundation’s mission is to advance the science of water to improve the quality of life. To achieve this mission, the Foundation sponsors studies on all aspects of drinking water, including resources, treatment, distribution, and health effects. Funding for research is provided primarily by subscription payments from close to 1,000 water utilities, consulting firms, and manufacturers in North America and abroad. Additional funding comes from collaborative partnerships with other national and international organizations and the U.S. federal government, allowing for resources to be leveraged, expertise to be shared, and broad-based knowledge to be developed and disseminated. From its headquarters in Denver, Colorado, the Foundation’s staff directs and supports the efforts of more than 800 volunteers who serve on the board of trustees and various committees. These volunteers represent many facets of the water industry, and contribute their expertise to select and monitor research studies that benefit the entire drinking water community. The results of research are disseminated through a number of channels, including reports, the Web site, Webcasts, conferences, and periodicals. For its subscribers, the Foundation serves as a cooperative program in which water suppliers unite to pool their resources. By applying Foundation research findings, these water suppliers can save substantial costs and stay on the leading edge of drinking water science and technology. Since its inception, the Foundation has supplied the water community with more than $460 million in applied research value. More information about the Foundation and how to become a subscriber is available on the Web at www.WaterResearchFoundation.org. ©2009 Water Research Foundation. ALL RIGHTS RESERVED Utility Guidance for Mitigating Catastrophic Vegetation Change in Watersheds Prepared by: Elizabeth M. Strange, Diana R. Lane, and Charles N. Herrick Stratus Consulting Inc., 1920 L Street, NW, Suite 420, Washington, DC 20036 P.O. Box 4059, Boulder, CO 80306-4059 Jointly sponsored by: Water Research Foundation 6666 West Quincy Avenue, Denver, CO 80235-3098 and U.S. Environmental Protection Agency Washington, DC 20460 Published by: ©2009 Water Research Foundation. ALL RIGHTS RESERVED DISCLAIMER This study was funded by the Water Research Foundation (Foundation) and the Environmental Protection Agency (USEPA) under cooperative agreement No. X-83294801. The Foundation and USEPA assume no responsibility for the content of the research study reported in this publication or for the opinions or statements of fact expressed in the report. The mention of trade names for commercial products does not represent or imply the approval or endorsement of the Foundation or USEPA. This report is presented solely for informational purposes. Copyright © 2009 by Water Research Foundation ALL RIGHTS RESERVED. No part of this publication may be copied, reproduced or otherwise utilized without permission. ISBN 978-1-60573-055-4 Printed in the U.S.A. ©2009 Water Research Foundation. ALL RIGHTS RESERVED CONTENTS TABLES ......................................................................................................................................... ix FIGURES ....................................................................................................................................... xi FOREWORD ............................................................................................................................... xiii ACKNOWLEDGMENTS .............................................................................................................xv EXECUTIVE SUMMARY ......................................................................................................... xvii CHAPTER 1: INTRODUCTION ................................................................................................... 1 Project Objectives ................................................................................................................2 Challenges Faced by Utilities Threatened by Large-Scale Vegetation Change ...................3 Why Preparation and Response Strategies Can Benefit Water Utilities ..............................4 Summary of the Project Approach .......................................................................................4 Structure of this Research Report ........................................................................................4 CHAPTER 2: IMPLICATIONS OF CHANGES IN WATERSHED SOILS AND VEGETATION FOR DRINKING WATER TREATMENT ..................................................... 7 The Influent Challenge .........................................................................................................7 Meeting The Influent Challenge ..........................................................................................7 Characterizing Changes in the Influent Challenge Resulting From Changes in Vegetation and Soils .................................................................................................10 Changes in Vegetation and Soils ............................................................................12 Altered Surface Runoff ..........................................................................................12 Altered Biogeochemical Cycling ...........................................................................13 Altered Infiltration Into Soils and Groundwater ....................................................13 Mobilization of Organic Matter, Organic and Inorganic Chemicals, and Micro-organisms .............................................................................................13 Altered Soil Erosion Potential ...............................................................................14 Landslides and Stream Channel Erosion ...............................................................14 Sediment-Altered River, Lake, or Reservoir Dynamics ........................................14 Responding to Changes in the Influent Challenge .............................................................15 CHAPTER 3: WILDFIRE ............................................................................................................ 17 Effects on Vegetation and Soils .........................................................................................17 Factors That Influence Fire Severity ......................................................................17 Factors Affecting the Frequency of Wildfire..........................................................19 Effects on Watershed Processes .........................................................................................21 Effects on Surface Water Quantity and Quality .................................................................22 Management Strategies ......................................................................................................23 Additional Information ......................................................................................................26 v ©2009 Water Research Foundation. ALL RIGHTS RESERVED CHAPTER 4: TIMBER HARVEST AND LOGGING ROADS .................................................. 27 Effects on Vegetation and Soils .........................................................................................27 Effects on Watershed Processes .........................................................................................27 Effects on Surface Water Quantity and Quality .................................................................28 Management Strategies ......................................................................................................29 Sediment Control ...................................................................................................29 Recovery of Vegetative Cover ...............................................................................31 Management for Diversity .....................................................................................31 Additional Information ......................................................................................................32 CHAPTER 5: STORMS ............................................................................................................... 33 Effects on Vegetation and Soils .........................................................................................33 Effects on Watershed Processes .........................................................................................33 Effects on Surface Water Quantity and Quality .................................................................34 Management Strategies ......................................................................................................35 CHAPTER 6: URBANIZATION ................................................................................................. 37 Effects on Vegetation and Soils .........................................................................................37