New Flood Risk Assessment Suggests Higher Risks Than Previously Thought


Via Flickr

Thomas Robinson | June 30, 2020

A new report from the First Street Foundation shows that flooding risk across the country is likely under represented.

New calculations reported in “The First National Flood Risk Assessment” suggest that almost twice the number of properties have a heightened flood risk compared to the FEMA Special Flood Hazard Area (SFHA) 1 in 100 layer.  The SFHA identifies properties with a heightened flood risk and influences decisions made for flood insurance and housing mortgages. FEMA identifies around 8.7 million properties to be at risk from a 100 year flood while the new risk assessment estimates 14.6 million properties to be at risk. 

To estimate the 14.6 million properties, the new report included small creeks that were ignored on federal maps, rainfall and sea-level rise.  The risk assessment includes areas where flood mapping is either incomplete or out of date which contributes to the increase in the number of at risk properties. 

For Iowa, the report suggested an additional 141,300 properties were at risk in the state compared with the SFHA measure.  The report identified Council Bluffs as the city with the most properties at risk (11,000 properties), followed closely by Des Moines (9,000 properties).

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