Updating flood inundation maps efficiently: building on existing hydraulic information and modern elevation data with a GIS

Flood maps produced by detailed Flood Insurance Studies (around 1980) in many cases are in need of updates to both the flood level used for the maps and to the elevation data used to delineate inundation areas. We have presented a cost-effective approach to making these updates using the results of the earlier detailed hydraulic studies, new high-accuracy elevation data, and geographic information system mapping technology. The resultant maps are as accurate and more detailed than the existing maps; easily produce important ancillary information such as detailed flood depth maps; facilitate flood impact assessment and planning; and are comparatively simple to store and distribute.