By Theresa Pinto M.S., Contributing Reporter
MIAMI BEACH, FLORIDA – Last month, researchers at Princeton University revealed an analysis that predicted the annual occurrence of ‘100-year floods’ along the Atlantic coastline and in the Gulf of Mexico.
For the analysis, researchers combined known data about storm surge and sea level rise, accounting for regional variations in sea level rise, with late 21st century predictions of increased tropical storm and hurricane activity. They then created a model of flood hazards at the county level along the U.S. East Coast and Gulf of Mexico.
The model showed that with the combined effects of stronger, more frequent hurricanes with sea level rise, ‘the historical 100-year flood level would occur annually in New England and mid-Atlantic regions and every 1–30 years in southeast Atlantic and Gulf of Mexico regions in the late 21st century.’
However according to Maggie Koerth-Baker, senior science writer for the analytical website FiveThirtyEight, the 100-year flood concept ‘obscures fundamental statistical problems in how we assess flood risks — problems that can lead to residents and homeowners believing themselves to live in a zone of safety that isn’t there.’
The 100-year flood measure has been around since 1973, when the government began implementing flood controls to regulate building height and mandatory flood insurance in floodplains. A 100-year floodplain meant there was a 0.1 percent chance each year of inundation on the land.
Yet there is a gap between the 8,000 data points collected from rivers and streams by the United States Geological Survey and the estimated flow rates that are turned into flood depth maps, according to FiveThirtyEight.
Flood insurance has its own controversial issues as well. Recently, a business analyst claimed the thirty-year mortgage in Florida was dead due to the impracticality of insuring homes for floods in the state.
Laura Read, a hydrometeorologist with the National Center for Atmospheric Research, told FiveThirtyEight, “But the bigger factor in flood map uncertainty could be how humans have changed the landscape and what we’ve built there.”
In 2017, Hurricane Harvey put one-third of Houston underwater when it made landfall, and the scientific consensus was that the urban landscape was a major factor in the flooding, highlighting Read’s point. Hurricane Harvey cost $125 billion in damage, according to the National Hurricane Center, matching Hurricane Katrina for costliest storm recovery.
Regardless of the what regulators call the risk of flooding, it is certain that incoming seas and other elements of climate change are increasing the frequency of flooding, and the concept of the ‘100-year flood’ is changing.