Last week, Hurricane Harvey devastated the city of Houston. The scale of the tragedy shocked even the National Weather Service. But perhaps the most shocked set of people is the 40 to 50 percent of Houstonians who live outside Federal Emergency Management Agency’s mapped high-risk flood zones and yet still found their living rooms underwater.
FEMA’s maps represent the government’s best estimates of flood plains. They hold a lot of power: When property isn’t included on FEMA’s “magical map,” its residents aren’t required to buy flood insurance. This tends to impart a false sense of security, says Rob Moore, senior water policy analyst at the Natural Resources Defense Council. “That’s why these flood maps lead to such risky behavior and have such tragic consequences.”
But as we have seen, both last week and in years previous, FEMA’s predictions are also frequently wrong. Why?
Some of the reasons are the ones you might have guessed. FEMA’s maps are backward-looking, often out of date, and based on historical flooding and development. They don’t anticipate trends pointing to the future of climate change and rising sea levels, shown by repeatedly flooded areas in Houston that lie outside of supposedly 100-year and 500-year flood zones. And, of course, 100-year and 500-year floods are occurring much more frequently than we’d expect, implying that those zones need to be updated. The maps also don’t account for rapidly expanding development in flood-prone suburban and exurban regions.
But another issue is the amount of control local politicians exert on these maps. As flood maps are developed, some local officials and communities have disproportionate influence on how they take shape. Politicians prefer to keep flood zones small to save their constituents money and allow for more development, according to new research by Sarah Pralle, a political scientist at Syracuse University, presented in San Francisco at the American Political Science Association’s annual conference on Thursday.
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