Outdated system is no match for worsening floods
HOUSTON — Houston’s system of bayous and reservoirs was built to drain a tabletop-flat city prone to heavy rains. But its Depression-era design is no match for the stresses brought by explosive development and ever-wetter storms.
Nearly any city would be overwhelmed by the more than 4 feet of rain that Hurricane Harvey has dumped since Friday, but Houston is unique in its regular massive floods and inability to cope with them. This is the third 100-year-or-more type of flood in three years.
Experts blame too many people, too much concrete, insufficient upstream storage, not enough green space for water drainage and, especially, too little regulation.
“Houston is the most floodprone city in the United States,” said Rice University environmental engineering Professor Phil Bedient. “No one is even a close second — not even New Orleans, because at least they have pumps there.”
The entire system is designed to clear out only 12 to 13 inches of rain per 24-hour period, said Jim Blackburn, an environmental law professor at Rice University: “That’s so obsolete it’s just unbelievable.”
Also, Houston’s Harris County has the loosest, least-regulated drainage policy and system in the country, Bedient said.
Here’s how the system is supposed to work: The county that encompasses Houston has 2,500 miles of bayous and channels and more than 300 stormwater holding basins, which are designed to fill up during intense downpours and drain slowly as high waters recede.
Water is supposed to flow west to east through bayous, which are tidal creeks that often have concrete improvements to make water flow and are connected to the Galveston Bay.
When big rains come, officials also activate two normally dry reservoirs, closing the floodgates to collect the water and keep it from overwhelming the downtown area.
But the main bayou through downtown Houston, Buffalo Bayou, “is pretty much still a dirt mud channel like you would have seen 100 years ago, just a little cleaned out,” said U.S. Geological Survey hydrologist Jeff East.
And because the coastal plain is so flat, the water doesn’t flow out of the bayous fast, Bedient said.
Also, some of the bayous, such as Brays, can handle only 10-year storms, he said. Harris County didn’t leave enough right-of-way space to expand its bayous, Bedient said. And widening projects have been slow and inadequate.
Now the reservoirs are overflowing. Officials are being forced to release some of the water pressing against the dams and backing up into wealthy subdivisions. But those releases could worsen the flooding downstream in Houston.
More reservoirs are needed, Blackburn and Bedient said. Another reservoir had been planned for Houston’s western prairies, but development killed that, they said.