GOING WITH THE FLOW IMPACTS OF CLIMATE CHANGE ON STORM INDUCED DEBRIS FLOWS IN HATZIC VALLEY, BC Liz Sutton Climate, Ocean, and Paleo-Environments (COPE) Laboratory School of Resource and Environmental Management, Simon Fraser University Climate change is expected to produce changes in precipitation patterns and these in turn could influence the potential for an increase of future debris flows (Dehn, Buma, & Gasparetto, 2005). Increased storm events caused by climate change could present significant natural hazards to sensitive areas in terms of community infrastructure, development sites, and public safety (Jakob & Weatherly, 2003). INTRODUCTION Debris flows are fast moving saturated sediment flows that are triggered as a result of high volumes of precipitation. Hatzic Valley and surrounding area have approximately 1350 residents inhabiting agricultural land and rural residential homes (Stats Canada, 2006). The eastern side of Hatzic Valley is a frequently active debris flow area, with the western side being less so. Since 1980, 15 reported debris flows have resulted from five specific storms causing damages to homes, roads, bridges, and other infrastructure in the area. Hatzic, BC Vancouver Mission Abbotsford U.S.A RESEARCH FOCUS This project focuses on three main research areas which will address: 1) Local debris flow initiation variables 2) Potential effects of climate change on meteorological variables of debris flows 3) Application of the research results to emergency preparedness and planning DATA Meteorological data collected by Environment Canada is currently being used to identify conditions of past storms which triggered debris flows. Environment Canada Mission West Abbey (MWA) station is the closest station to Hatzic Valley with a record extending from 1962 to present. In January of 2010 a HOBO data logger was installed to collect in situ meteorological data from an active debris flow site along the eastern slope of Hatzic Valley. Comparison of the MWA and COPE HOBO-1 will be used to determine if there is a significant difference in meteorological conditions based on the location of the station. METHODS Storms that produced debris flows will be compared with similar storms which did not produce flow events in order to isolate which meteorological variables are most influential in debris flow initiation. Meteorological mechanisms which have been found to contribute to debris flows are antecedent precipitation, as well as intensity and duration of storms. Antecedent precipitation will be measured in 1,2,3, and 4 week totals, while intensity/duration events will be assessed by rate of rainfall over the duration of the storm. Physical variables including geology, soils, slope, and topography will be considered within the specific local setting. Previous studies in other areas of BC suggest that discriminate function analysis and cluster analysis are appropriate analytical tools. Day of storm Source: Environment Canada Figure 2. Pattison Creek in Hatzic Valley, an active creek for debris flows and floods. Figure 1. Study Area: Hatzic Valley debris flows locations PROJECT RATIONALE The primary research goal is to identify climatic and geomorphic variables which have historically initiated debris flows in Hatzic Valley in order to develop criteria for forecasting events under similar conditions. Meteorological variables are being considered within the context of climate change to determine whether debris flow inducing storm conditions are likely to increase or decrease in the future. THANKS TO: Figure 3. COPE HOBO-1 was deployed January 2010 to collect meteorological data near Pattison Creek. Days before storm (antecedent) Figure 4. week antecedent precipitation for January 29, 2004 storm initiating debris flow at Carratt Cr. And Field Cr. Figure 5 Local historical precipitation trends from Agassiz CDA, the longest running MET station in the Fraser Valley A CHANGING CLIMATE Total annual precipitation between 1900 and 1998 has increased by 22% on average across British Columbia which is consistent with a general increase in precipitation throughout the Pacific Northwest (Pacific Climate Impacts Consortium, 2007). A study of the effects of climate change on the frequency of slope failures in south-west BC shows that antecedent precipitation is expected to increase by 10% by the end of the 21st century (Jakob and Lambert, 2009). Based on these findings, it is plausible that the frequency of debris flows in south-west BC will increase over time which will have implications for land-use and public safety planning.