Risk MAP Success Stories

Challenge: The Base Flood Elevation (BFE) is how high floodwater is likely to rise during a 1%-annual-chance flood event. It is one way to measure and indicate flood risk. However, the study that established the BFE is only a snapshot in time. There are many factors that can cause floodwaters to rise above the BFE. These factors include debris-blocked bridge and culvert openings; blocked city storm sewer drains; higher-intensity rain events; storm tracks causing coinciding peak flows of flooding sources; high backwater conditions; and heavy rains on frozen ground with considerable snow depths. There is also always the potential for an event more severe than the 1%-annual-chance event. To communicate and reduce flood risk in areas beyond FEMA’s regulatory flood zones, communities need more information (especially spatial information) about flooding that exceeds the 1%-annual-chance event.