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Two pilot studies were conducted in the Nisqually and Snoqualmie River Basins to investigate the use of two methods developed for mapping flood hazard areas using state-of-the-art data, technology, and software to improve the efficiency, accuracy, and timeliness of flood mapping. The first pilot was conducted in the lower reach of the Nisqually River Basin of western Washington, to develop a method for updating existing Flood Insurance Rate Maps (FIRMs) efficiently. These maps are used for zoning and planning purposes in addition to determining Federal insurance requirements. The method was developed using hydraulic models from existing Flood Insurance Studies (FISs), high accuracy elevation data, and Geographic Information Systems (GISs). The second pilot study was conducted in the Nisqually River Basin of western Washington and the Snoqualmie River Basin east of Seattle, Washington, to create inundation maps of flood forecasts issued by the National Weather Service (NWS) and deliver them in near real-time over the Internet. There were two methods used to generate the inundation maps. For the Nisqually River Basin, the maps were generated using the methods developed in the first pilot: Updating Existing Flood Maps Efficiently. For the Snoqualmie River Basin, the maps were generated using a two-dimensional hydraulic computer model and a GIS: Mapping NWS Flood Forecasts. Both types of maps are distributed over the Internet in near-real time using emerging Internet map server software. |
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