![]() ![]() In analyzing the damage from Hurricane Harvey in the Houston area, I found that Black and Hispanic residents disproportionately experienced flooding in areas beyond FEMA’s 100-year flood zones. But most local governments have less understanding of the social and demographic composition of communities that experience flood impacts outside of flood zones. Years of research and evidence from storms have highlighted social inequalities in areas with a high risk of flooding. Racial disparities in flooding outside the zones ![]() So far, FEMA hasn’t taken into account the impact climate change is having on extreme weather and sea level rise. If greenhouse gas emissions continue to increase at a high rate, computer models suggest that the chances of a severe storm dropping 20 inches of rain on Texas in any given year will increase from about 1% at the end of the last century to 18% at the end of this one, a chance of once every 5.5 years. Third, the era of climate change scuttles conventional assumptions.Īs the planet warms, extreme storms are becoming more common and severe. FEMA-delineated flood zones are the major factor shaping flood mitigation behaviors. The logic goes: if I’m not in the 100-year floodplain, then I’m not at risk. Second, binary thinking can lead people to an underaccounting of risk, and that can mean communities fail to take steps that could protect a neighborhood from flooding. FEMA is required to assess whether updates are needed every five years, but the majority of maps are older. Famously, New York City was updating its maps when Hurricane Sandy hit in 2012 but hadn’t finished, meaning flood maps in effect were from 1983. Moreover, the process for updating floodplain maps is locally variable and can take years to complete. Urbanization matters because impervious surfaces – think pavement and buildings – are not effective sponges like natural landscapes can be. Three reasons stand out.įirst, some places rely on relatively old FEMA maps that don’t account for recent urbanization. Understanding why areas outside the 100-year flood zones are flooding more often than the FEMA maps suggest involves larger social and environmental issues. Other researchers find an even higher margin, with 2.6 to 3.1 times more people exposed to serious flooding in a 100-year storm than FEMA estimates. One of those models, from the First Street Foundation, estimates that the number of properties at risk in a 100-year storm is 1.7 times higher than the FEMA maps suggest. New risk models point to a similar conclusion: Flood risk in these areas outstrips expectations in the current FEMA flood maps. Harris County, home to Houston, now recommends all households have flood insurance, whether they’re in a FEMA flood zone or not. ![]()
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