The Accuracy of Flood Maps
Scientists blame global warming for the rise of sea levels, stating higher seas will cause more coastal flooding in this century and beyond in places that have ordinarily been dry and out of harm’s way. However, mapping where these future floods will strike has barely begun.
“Flooding remains the most common and most costly form of natural disaster in the United States, and insurance to protect against it has become increasingly necessary in certain places. A report this month from the Union of Concerned Scientists suggests an ominous future. Within the next two decades, it forecasts that nearly 170 U.S. coastal communities will face chronic inundation, defined as flooding at least 26 times a year. That’s almost twice as many at-risk locations as today.” — The Washington Post
The Federal Emergency Management Agency (FEMA) maps demonstrate which people are at moderate or high risk of flooding. “Most people with property in hazardous areas — where the annual risk of a flood is one in a hundred or more — are required by law to buy federal flood insurance from FEMA’s National Flood Insurance Program,” shared NPR. However, FEMA’s maps are based on past patterns of flooding. The expected sea level rise to come with its new and larger flood zones — isn’t currently considered when determining the flood zones.
Some communities are taking it upon themselves to create their own more accurate maps that predict future flooding. These maps can be used in both commercial and residential real estate transactions, development, and by current property owners. It is evident why the results of inaccurate mapping could be both disastrous and deadly.
Yet, how is one to know where flood zones will be when sea level rises?
NPR shared that city planners in flood-prone Annapolis “asked the Army Corps of Engineers to show them how the flood zone would expand if sea level here rises 3.7 feet — a midrange prediction for 2100. They found that a flood from a one-in-a-hundred year flood would be almost twice as high as it would be if such a storm hit now.” Though property owners may own homes and businesses that aren’t currently located within a flood zone, that could change far sooner than ever imagined.
In addition, references to “one-in-a-hundred year flood” or the “100-year floodplain” are often confusing to many people. While seemingly referring to a flood that only happens every 100 years — well outside the horizon for the majority of home buyers — the term actually indicates a property that has a 1% risk of flooding every year.
Rather than erring on the side of caution and opting in to buy flood insurance they aren’t currently required to obtain, most residents attempt to avoid the purchase at all cost. “Ninety percent of the people that have called me over the past 20 years want to get out of paying for flood insurance,” said floodplain engineer David Guignet to NPR.
Guignet stresses the importance of owners understanding if their property is in the path or under threat of rising sea levels. This knowledge would allow them to have a better understanding of timing — whether it’s selling a property or making alterations in design that could be life-saving.
FEMA is currently struggling to update its existing flood maps as “precision costs money.” Fixing its maps would include incorporating digital elevation data and factoring in the future risks of climate change. And, according to scientists, sea levels are rising at an accelerating pace. FEMA and communities need to move even faster to insure the protection of civilians.
