Creating a national scale floodplain map for the United States using soil information

Abstract:

Floods are the most damaging of all natural disasters, adversely affecting millions of lives and causing financial losses worth billions of dollars every year across the globe. Flood inundation maps play a key role in the assessment and mitigation of potential flood hazards. However, there are several communities in the United States where flood risk maps are not available due to the lack of the resources needed to create such maps through the conventional modeling approach. The objective of this study is to develop and examine an economical alternative approach to floodplain mapping using widely available gSSURGO soil data in the United States. The gSSURGO dataset is used to create floodplain maps for the entire United States by using attributes related to soil taxonomy, flood frequency and geomorphic description. For validation, the flood extents obtained from the soil data are compared with existing maps, including the Federal Emergency Management Agency (FEMA) issued Flood Insurance Rate Maps (FIRM), flood extents observed during past floods, and other flood maps derived using Digital Elevation Models (DEMs). Preliminary results show that overlap between the SSURGO based floodplain maps and FEMA maps range from 65 to 90 percent. While these results are promising, a more comprehensive validation of these maps must be conducted. The soil based approach floodplain mapping approach offers an objective, economical and faster alternative in areas where detailed flood modeling and mapping has not been conducted.