Current Midwest flooding highlights strengths and weaknesses of FEMA mapping program

By David Jacobson, Temblor

Check your flood risk

Flooding in Missouri has left this golf course completely unplayable. Up to 12 inches of rain fell over the weekend with more to come over the next few days. (Photo from: ABC News)


Over the weekend, torrential rain in Missouri, Arkansas, Oklahoma, and Illinois caused flooding, resulting in disruption and left at least 20 people dead. Depending on the location, between 6 and 12 inches of rain fell, leading to evacuations and hundreds of road closures. For many of these states, this is the most severe flooding in over 100 years, and many records have been smashed. Unfortunately, a new front is moving towards the area, which is expected to dump another 4-6 inches of rain on the already inundated area. Because of the scale of some of these floods, here we compare how well the flooding follows the FEMA flood maps.

The flood maps created by FEMA are intended to “identify flood hazards, assess flood risks, and provide accurate data to guide stakeholders in taking effective mitigation actions that result in safer and more resilient communities.” These maps are then used to support the National Flood Insurance Program, which lays out requirements for flood insurance. According to these requirements, only people who have a mortgage and are living in areas where there is a 10% chance of flooding per decade are required to carry flood insurance. By examining the scale of flooding, we can see if the maps accurately show where flooding is most likely. FEMA acknowledges that flood hazards can change due to weather patterns, erosion, and new development. Therefore, maps are periodically updated to reflect changes. Nonetheless, this can take time meaning some people may be at risk without knowing it.

Eureka High School in Eureka, Missouri has been completely flooded due to recent rainfall in the Midwest. As is evident from the Temblor figure, flooding appears to have occurred almost exclusively within the 10% chance per decade zone. (Top photo from: David Carson/St. Louis Post-Dispatch via AP)


Interstate 44 in southern Missouri was forced to close due to floodwaters overtaking it. Once again, the flooding occurred in an area with a 10% chance of flooding per decade. (Top photo from: Missouri State Highway Patrol)


For these locations, flooding is taking place in the 10% chance per decade zones. However, FEMA coverage is not complete. For example, the very small town of Van Buren, Missouri, which has been turned into a lake (see below), has not been mapped by FEMA. Unfortunately, this lack of information could lead to people thinking they are not at risk, when in fact they are.

Despite the fact that Van Buren, Missouri has seen extreme flooding from recent rainfall, residents would not know whether they are in FEMA flood zones because the area has not been mapped. (Photo from: Missouri State Highway Patrol)


This map shows areas with FEMA flood mapping coverage in parts of the Midwest. Unfortunately, many areas in southern Missouri experienced extreme flooding from heavy rain over the weekend.


What all of this information shows is that it is essential we have accurate flood maps for everyone at risk. Because a person’s home is likely to be their most valuable asset, protecting it is essential to their well-being. Knowing how at risk you are to flooding not only impacts if you are required to carry flood insurance, but influences where people may buy a house or whether or not they want to purchase insurance when it is not compulsory. Without this knowledge people could be lured into a false sense of security.


The Weather Channel
The Washington Post
ABC News