Applying Future Conditions Flood Models to Hazard Mitigation Planning

The 100-Year floodplain is a central driver of both federal flood insurance requirements and local land development policy in the United States. Yet maintaining accurate floodplain delineations is an ongoing challenge. The process of urbanization tends to result in more frequent high-magnitude flood events, effectively expanding the 100-Year floodplain. As a result, the delineated 1% probability flood is often not representative of the actual probability of flood damage. Land use planning has been cited as a key component of addressing the shortcomings of floodplain management policy because it governs the placement, use, density and standards for new development. However, land use planners do not have a ready supply of alternative delineations as authoritative as the 100-Year floodplain to use as the basis for development permitting. Additionally, there is little consensus on the best land use planning paradigm or development pattern to emulate for hazard mitigation purposes. Different urban development configurations have been found to result in different spatial distributions of peak discharge, but little is known about the degree to which the location and configuration of future development affects the future 100-Year floodplain and overall levels of flood risk. This project demonstrates a process by which land use planners can evaluate the hazard mitigation potential of different land use configurations using future conditions hydrologic and hydraulic models coupled with a flood risk assessment. The proposed process incorporates feedbacks between urban development, hydrology, and flood risk using standard land use planning techniques and existing engineering models