Flood Damage Estimates Using GIS Spatial Analysis

by Craig R. Wilkening, (A.M.ASCE),

Abstract: The catastrophic flooding in the midwest during the Summer of 1993 and in California in the Spring of 1995 resulted in flood damage estimates in the hundreds of millions to billions of dollars. Throughout the U.S., millions of structures are unprotected from flooding because of past floodplain management policies, budget limitations, and/or lack of adequate information on floodplain boundaries. As communities along rivers and streams become more aware of potential flood hazards, increased emphasis will be placed on the development of structural and non-structural flood control improvements and the effects of these improvements on the water surface elevations of various frequency floods. Equally important will be the analysis of the costs and benefits of these flood control improvements. Flood damage analysis methods in the past have required tedious inventories of all of the structures in a floodplain in order to determine the water surface elevation-damage curves for each land use in a stream reach. In this study, a Geographic Information System (GIS) was used to develop the elevation-damage curves along a sample stream reach in Colorado. Using a Digital Elevation Model (DEM) and land parcel data, the GIS was used to determine the parcel elevations from the DEM. The GIS was also used to overlay the land use, parcel, structure value, and water surface data on the DEM and to compile the elevation-damage information using the data base capability of the GIS. The resultant elevation-damage curves are then input back into the GIS in order to develop a graphical representation of the damages as the water surface elevations increase. With the power of GIS technology, much of the tedious data development can be reduced or eliminated, and the output displayed in a graphical format gives the engineer or floodplain manager an additional tool to effectively analyze flood control alternatives.

Subject Headings: Geographic information systems | Spatial analysis | Floods | Damage (structural) | Water surface | Flood frequency | Rivers and streams | Curvature | Information management | Data processing | North America | United States | California | Colorado | Mid-West states

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