A map compiled using data and risk assessments by the Federal Emergency Management Agency (FEMA) shows the counties in the U.S. that are currently deemed to be the most, and least, at risk of being vulnerable to flooding from rivers.
According to the figures, Harris County in southeastern Texas has the highest determined risk of suffering from riverine flooding, while Galveston and Brazoria counties also have a "very high" risk index.
East Baton Rouge, Lafayette and St. Tammany counties in Louisiana, Shelby County in Tennessee, Miami-Dade County in Florida and Orange County in Texas all rank among the top ten in terms of determined risk due to river flooding.
Conversely, the county with the lowest risk due to riverine flooding is Otsego in Michigan, with an index figure of just over two percent. Other counties have no rating or insufficient data to make a determination.
The map is one of several developed by FEMA to track natural hazards across the U.S. Other maps include the evaluated risk of hurricanes, droughts, heatwaves and wildfires—as one that gives a general assessment of risk to natural hazards.
The federal disaster agency says the assessments show the areas that are the "most at risk from the effects of natural hazards and climate change," and are used as a "geographic focus for financial and technical assistance."
Experts agree that as the climate gets warmer on average, more energy will be pushed into the atmosphere, energizing weather systems and making them more erratic. This means that extreme weather events will occur with greater severity, often causing greater hardship to human populations.
The FEMA risk indices are calculated by multiplying the expected annual economic loss due to the natural hazard by the areas' relative vulnerability to be adversely impacted by natural hazards. This is then divided by a score of the communities' resilience and preparedness to those hazards relative to other communities that face similar challenges.
As such, an area's risk score does not represent how likely it is to suffer a natural hazard but rather how it compares to other counties in coping with the risks it has previously suffered.
In January, flooding occurred in parts of southeastern Texas due to excessive rainfall. Rising water in Lake Conroe in Montgomery County—which has a "relatively high" risk of riverine flooding—threatened major downstream flooding into Harris County, which has a "very high" riverine flooding risk.
Among the top 25 counties in terms of riverine risk are Kern, Ventura and San Bernardino counties in California—all of which have a risk index above 99 percent, or "relatively high."
The risk assessment appears to be ringing true, as a powerful atmospheric river storm which made landfall on Monday in southern California has led to flooding in the regions, with the National Weather Service reporting sections of the San Bernardino bursting their banks.
Powerful atmospheric river storms have already caused areas of flooding and mudslides and several deaths, prompting Gov. Gavin Newsom to declare a state of emergency for several counties earlier in February.
Around the same time last year, California was battered by a succession of deadly storms that brought severe flooding—the severity of which was attributed to climate change.
Uncommon Knowledge
Newsweek is committed to challenging conventional wisdom and finding connections in the search for common ground.
Newsweek is committed to challenging conventional wisdom and finding connections in the search for common ground.
About the writer
Aleks Phillips is a Newsweek U.S. News Reporter based in London. His focus is on U.S. politics and the environment. ... Read more
