Flooding in excess of 100-year recurrence interval streamfiows occurred in Georgia along the Flint and Ocmulgee Rivers and their tributaries in July 1994 as a result of rainfall from Tropical Storm Alberto. In order to facilitate mitigation of flood damages, a variety of spatial information was required by Federal, state, regional, and local agencies as well as by utility companies. An interagency spatial information team was assembled immediately following the flood at the request of the Federal Emergency Management Agency. The U.S. Geological Survey led the formation of this team, which consisted of representatives from 22 Federal, State, and local agencies. This team rapidly constructed spatial-data sets for use by team participants and other entities assisting communities with flood-recovery efforts. In the aftermath of the devastating floods in the Mississippi River basin in 1993, a similar interagency floodrecovery team was formed to identify and supply spatial-data sets using geographical information system (GIS) technology. Using the interagency team formed after the Mississippi flood as an example, the interagency team in Georgia identified and assembled spatial-data sets needed to delineate flood extent, estimate flood-recurrence intervals at selected stream locations, support short- and long-term recovery plans, and document the historic flood event caused by Tropical Storm Alberto. Currently, spatial data collected by the USGS and regional flood-estimating equations are being used to develop experimental flood-extent models. When coupled with computerized three-dimensional visualization tools under development by the Georgia Tech Research Institute staff, a flood-extent model could depict a flooded area in a readily understandable manner. If successful, this experiment could lead to calibrated flood-extent models suitable for coupling with real-time stream-stage information. Such modeling tools could be useful for monitoring flood extent in real-time and for making flood-extent warnings and predictions. One important use of visual presentations of flood-extent model outputs would be to convey the effects of flooding on homes, businesses, agriculture, and civil infrastructure to the public.
KEY WORDS: Flooding, Georgia, spatial data, geographical information system