A flash flood risk assessment of the Colorado

Although significant research has been performed on impacts and mitigation of flash flood events, the methodology for assessing social vulnerability and regions at risk has not been fully developed. This project explored the environmental-social links of flood hazards and developed a GIS-based methodology for flood risk assessment. The assessment was based on a model that risk was a product of exposure to a hazard and societal vulnerability. Vulnerability was represented by population characteristics and distribution of critical facilities. Exposure was estimated by combining the Areal Mean Basin Average Rainfall (AMBER) method combined with GIS techniques. This method involved relating precipitation accumulation, averaged over a stream basin, to National Weather Service flash flood guidance values to identify basins with flooding potential. The vulnerability and the exposure were integrated in a GIS to estimate the total risk. The 1997 extreme precipitation event in Fort Collins, Colorado was used as a model to assess potential flood risk in two metropolitan areas: Fort Collins and Denver. Results yielded a GIS-based model that combines hydrometeorological information with social data, and allowed for radar-derived precipitation data to be integrated into the GIS to map key areas at risk in Fort Collins and Denver. Early identification of risk areas can assist emergency and flood-plain managers in developing response and mitigation measures. These results can provide a framework to expand this study of flood risk by introducing near-real time precipitation data, hydrological models and, detailed socio-economic geographic data.