While nobody expects 50 inches of rain to fall in one storm, Houston is still badly situated to withstand flooding even from lesser weather events due to its location on a flood plain:
Houston is built on what amounts to a massive flood plain, pitted against the tempestuous Gulf of Mexico and routinely hammered by the biggest rainstorms in the nation.
It is a combination of malicious climate and unforgiving geology, along with a deficit of zoning and land-use controls, that scientists and engineers say leaves the nation’s fourth most populous city vulnerable to devastating floods like the one caused this week by Hurricane Harvey.
“Houston is very flat,” said Robert Gilbert, a University of Texas at Austin civil engineer who helped investigate the flooding of New Orleans after Hurricane Katrina. “There is no way for the water to drain out.”
Indeed, the city has less slope than a shower floor.
Harvey poured as much as 374 billion gallons of water within the city limits, exceeding the capacity of rivers, bayous, lakes and reservoirs. Experts said the result was predictable.
The storm was unprecedented, but the city has been deceiving itself for decades about its vulnerability to flooding, said Robert Bea, a member of the National Academy of Engineering and UC Berkeley emeritus civil engineering professor who has studied hurricane risks along the Gulf Coast.
The city’s flood system is supposed to protect the public from a 100-year storm, but Bea calls that “a 100-year lie” because it is based on a rainfall total of 13 inches in 24 hours.
“That has happened more than eight times in the last 27 years,” Bea said. “It is wrong on two counts. It isn’t accurate about the past risk and it doesn’t reflect what will happen in the next 100 years.”
Some of the blame (a lot of the blame) for locating vulnerable properties in flood-prone areas is due to the US government’s flood insurance program:
Texans, watch out. An aftershock is following behind the catastrophic flooding produced by Hurricane Harvey in coastal Texas: The National Flood Insurance Program (NFIP) is coming up for reauthorization.
The main lesson that the public and policymakers ought to learn from Harvey is: Don’t build in flood plains, and especially don’t rebuild in flood plains. Unfortunately, the flood insurance program teaches the exact opposite lesson, selling subsidized insurance whose premiums do not come close to covering the risks home and business owners in flood prone areas face.
As a result, the NFIP is currently $25 billion in debt.
Federally subsidized flood insurance represents a moral hazard, Kevin Starbuck, Assistant City Manager and former Emergency Management Coordinator for the City of Amarillo, argues, because it encourages people to take on more risk because taxpayers bear the cost of those hazards.
Federal Emergency Management Agency data shows that from 1978 through 2015, 3.8 percent of flood insurance policyholders have filed repetitively for losses that account for a disproportionate 35.5 percent of flood loss claims and 30.5 percent of claim payments, Starbuck says. Most of these properties were grandfathered in before the NFIP issued its flood insurance rate maps. The NFIP is not permitted to refuse them insurance or charge them rates based on the actual risks they face.
Clearly, taxpayers should not be required to subsidize people who choose to build and live on flood plains. When Congress reauthorizes the NFIP, it should initiate a phase-in of charging grandfathered properities premiums commensurate with their risks. This will likely lower the market values of affected homes and businesses and thus send a strong signal to others to avoid building and living in such risky areas.
