Predictive and Observational Flood Mapping

摘要

IF YOU HEAR THE PHRASE "flood map" in the United States, what usually springs to mind are regulatory maps constructed by the Federal Emergency Management Agency (FEMA) to identify the 100-year and 500-year floodplains in American communities. These are static maps developed from statistically defined precipitation and streamflow events. However, inundation during an actual flood event is dynamic with flow in the stream network rising and falling in response to the local storm precipitation, which itself is highly variable in space and time. Flood inundation based on the Height Above Nearest Drainage (HAND) principle relies on defining for each point in the landscape the vertical height of the land surface relative to the elevation of the streambed to which it drains. This enables the creation of contour map of relative elevation of the landscape above the streambed, as shown in Figure 1. This provides a very effective flood mapping approach, supporting both predictive flood mapping using forecast models for flood discharge, and observational flood mapping based on the current location of the water's edge.