![]() The update process is time-consuming, with a lengthy statutory consultation and appeals process.Įven if communities have more recent data, FEMA will not publish a partial update. But a recent Congressional Budget Office report found that two-thirds of counties with high flood-related claims had maps that were more than five years old. And the maps do not analyze how risks vary within flood zones, or between coastal and inland locations.įEMA is required to assess whether the maps need updating maps every five years. This can give residents in those zones a false sense of security. For instance, FEMA often assigns low flood risk to locations that are near coasts but slightly elevated, due to insufficient wave modeling to account for storm surge risk. ![]() They do a poor job of accounting for changing conditions. If they are inaccurate, they may mislead users.Īnd the maps have widely-recognized flaws. When homeowners elevate or flood-proof their homes or purchase flood insurance, they may also influence neighbors to take similar steps.įEMA's maps can be a double-edged sword. It's close to where you are, so you have more risk of flooding than somebody further away.'" A civil engineer who worked for the city of Huntsville, Alabama told me that he used the maps to point out relative risks to homeowners: "I'll say, 'Do you have flood insurance? You don't have to – your house isn't in – but you do have one-percent annual chance floodplain on the back of your property. FEMA also works with local governments to educate residents about flood risks. How do these maps convey risk? Using websites such as, users can view the flood maps and see threats to their properties and surrounding areas. Working with other social scientists and engineers, I found that people who live in communities with a large percentage of 100-year flood zones are more likely to buy flood insurance, even when they are not required to do so. Using surveys and geographic data, I have shown that flood maps significantly affect voluntary decisions to purchase flood insurance. Some Houstonians who are not required to elevate their homes are choosing to do so. Homeowners there must buy flood insurance in order to qualify for federally regulated or guaranteed loans. Since this translates to 100 percent odds of flooding at least once in a century, these areas often are referred to as 100-year flood zones (creating the misleading impression that they will only flood once a century). On the maps, Special Flood Hazard Areas identify zones with a one percent chance of flooding in any given year. They determine insurance rates, inform local regulations and communicate risks to communities FEMA's flood risk maps receive less attention, but are a powerful risk communication tool.įEMA produces these maps for more than 20,000 communities that participate in the insurance program. Much discussion about the troubled National Flood Insurance Program has centered on its artificially low premiums. I believe choosing to rely on faulty information, driven by short-term financial concerns, will increase long-term risks for many Houstonians. This avoids requirements such as elevating houses and buying flood insurance. ![]() In just one example, officials in the city of Friendswood (part of greater Houston) are allowing some residents to rebuild their homes based on outdated flood risk maps that greatly underestimate the risk of future floods. After last year's flooding, it would be logical to expect affected communities to rethink long-term hazard management and risk reduction. Harvey's impacts in Houston provide an ideal case study for unsustainable human-environment interaction. The National Flood Insurance Program, administered by the Federal Emergency Management Agency (FEMA), unintentionally encouraged intense development by offering coverage in flood-prone areas at below-cost rates. With no formal zoning or comprehensive plan, developers were allowed to turn virtually any land, including wetlands, into houses and shopping malls. Before Harvey, Houston was widely known as a model of unchecked urban development.
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