Estimates say 240 billion gallons of water have fallen on Houston over the last few days, bringing historic floods. But the damage they've caused is at least partly avoidable, according to a professor who studies the phenomenon.
Houston has a long history of flooding. And as the city has grown into America's fourth largest city, losses of life and property from chronic flooding have grown along with it.
Between 1999 and 2009, Houston incurred just over $3 billion in insured losses alone. But such losses are not inevitable, said Samuel Brody, a professor of marine sciences, landscape architecture and urban planning at Texas A&M University.
"Flooding is a natural phenomenon," Brody said. "Flood losses, flood damage, people losing their homes and their lives, that is something we can control, by smarter planning, smarter development."
The real problem, in a word, is the stuff that's covering most of the flood-prone region: pavement.
"We calculated that between 1996 and 2011, the Houston region increased its pavement, its impervious surface coverage, by about 25 percent, which is hundreds of square miles of pavement."
"Pavement, to me, is the problem," Brody said. Pavement is impermeable — it does not absorb water. When rain falls, or when ocean waves drive seawater onto land during intense storms, the water simply collects at the surface.
"Every square meter of pavement in Houston, on average, translates into about $4,000 of extra flood damage," he said.
And as Houston has grown at a quick pace over the last few decade, institutions public and private have not factored enough flood protection and preparation into development.
"We calculated that between 1996 and 2011, the Houston region increased its pavement, its impervious surface coverage, by about 25 percent, which is hundreds of square miles of pavement," Brody said.
And that is only likely to continue. An additional 90,000 people settled in Houston last year, and the region is expected to grow by 3.7 million people over the next 30 years, according to Brody's recent research.
Better flood planning requires efforts from multiple levels of government and community, from the individual homeowner to the local neighborhood and beyond, Brody said.
For one thing, flood planning cannot simply be left to individual real estate developments or neighborhoods. The numbers about how much rain has fallen in the area are somewhat misleading, since the rain has not fallen evenly across the entire Houston area.
"There are some areas that have received 18 inches, and others that have received three," he said.
The heaviest rains have fallen in the northwestern part of the region. Yet that water will eventually travel south toward the bay, flooding areas along the way. To some extent, planning has to be regional
At the same time, Brody said individuals need to be educated about what to do during floods — moving their belongings to a second floor or attic if they have one, and knowing where the high water mark is, for example. Neighborhoods can do things such as ensuring that storm drains are clear of debris.
Changing building codes would also help. Brody and his colleagues have done national studies examining strategies that mitigate flood damage. Their research concluded that elevating structures was the number-one strategy for reducing property losses.
Designating especially vulnerable areas in the floodplain as protected open spaces — which often requres buying property back from owners — could also save a lot of money for communities overall.
There are technological solutions as well, such as porous or permeable concrete and asphalt mixes. Some of those mixes can absorb and divert massive amounts of water.
Such inventions are potentially valuable, but they would only really work as part of a larger strategy, Brody said.
"I think educating the public and giving the public the tools to make informed decisions before they take on major investments is really critical," Brody said. "A lot of the discussion is about bigger pipes, or bigger retention ponds, but really we need to convey the risk to the individual resident who ends up taking the burden for governmental failure.
"I don't want to say all levels of government are failing," he continued. "Particularly, the Harris County Flood Control District and city of Houston are doing the best they can with limited resources. But it is a real problem, and it is just going to get worse."