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2-(>J't. FLOODS FOLLOWING FIRE Buffalo Creek Flood Ev{~nt of July 12, 1996 ABSTRACT Prepared for ASFPM 1997 Annual Conference "Floodplain Management in a Multifaceted World" by Thomas W. Browning, Colorado Water Conservation Board Brian R. Hyde, Colorado Wat',r Conservation Board On the night of July 12, 1996, a flash flood occurred in the cDmmunity of Buffalo Creek, which is within an unincorporated area of Jefferson County, Colorado. Buffalo Creek lies at an elevation of 6800 feet and is located about 30 miles southwest of Denver in the foothills of the Front Range. A thunderstorm in the area produced heavy rainfall over a short period of time. Major flood flows occurred along Sand Draw, Buffalo Creek, the North Fork of the South Platte River and several other tributary streams in the area. Two lives were lost as a direct result of the flooding. Roads, bridges, utilities, public facilities, homes, outbuildings, ana vehicles were damaged or destroyed as well. The Buffalo Creek flood event was trllly a disaster, with total flood related damage, estimated to be over 5 million dollars. On May 18-19, 1996, less than two months prior to the flood event, an intense wildfire burned approximately 12,000 acres of forested land in the Buffalo Creek area. Vegetative and sDil conditions in the severely burned areas of the watershed were changed dramatically from their pre-fire conditions. The resulting hydrophobic (water repellent) soils and the loss of vegetative cover and humus layer have greatly changed the hydrologic response of the affected watershed. Based on field surveyed cross-sections and high water marKs, the July 12 flood flows on several streams in the Buffalo Creek area were estimated to be from 7 to 25 times the published FEMA ] OO-yr flows. The S,md Draw_'O@tershed, which experienced severe burning and has a drainage area of onlLLCi.sguare miles, produced unit dischill:r&s (~n the order of 5,000 cfs per SQuare mile during the flood. The rainfalll!mount has been preliminarily estimated to be slightly higher than the published] -hour, l00-year rain for that area of Colorado. Unfortunately, the community will be at a high risk for flash flooding for a very long time. Based upon previOLlS and current research, it will likely take tens of years for the Buffalo Creek watershed to fully recover from the affects of the wildfire, if it does fully recover. Forest fires, which can be triggered naturally or as a result of human activity, are a common occulTence in many area.' of the United States. In Colorado, large portions of the Front Range as well as much of the high country in western Colorado face very high forest fire danger (witness the deaOly Storm J(ing Mountain fire in 1994). Much of Colorado's population growth is OCCUlTing in these fire-prone areas. The critical issue for floodplain managers, hydrologists, forest managers, and meteorologists is to identify those communities and developed areas that are at high flood risk following wildfires. As proven with the case of Buffalo Creek, two disasters can strike a community within a very short period of time. Both sh0l1-term and long-term mitigation strategies need to be in place so that floodplain managers and vulnerable communities can be prepared for "floods following fire." The CWeB has developed a mitigation plan to assist the community and the local government with pre- and post-flood considerations. The strategies presented in the mitigation plan should help to lessen the loss of life and property when l1ash floods occur in the future. Those strategies can be easily adapted to other flood prone communities within burned waters.heds, and within watersheds facing a high risk of future fires. One of the most exciting and important aspects of the nood documentation and mitigation planning was the involvement and cooperation of local residents and numerouS fecleral, Slate, and local government agencies. Within the proposed paper/presentation for this conference, the CWCB will be presenting information regarding documentation of the fire and flood events. In addition. the Buffalo Creele mitigation plan will be presented as a model for other fire/flood prone communities. The integration of numerous disciplines and agencies as well as multiple natural hazards within the mitigation plan truly rJpresents multi-faceted flooclplain management.