Houston drainage grid ‘so ob­so­lete it’s just un­be­liev­able’

The Reporter (Lansdale, PA) - - WEATHER - By Seth Boren­stein and Frank Ba­jak

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 flood-prone 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 24hour 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 en­tire 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 storm-water 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, who is based in Houston.

And be­cause the coastal plain is so flat, only slop­ing about a foot per mile, the water doesn’t flow out of the bay­ous fast, Be­di­ent said.

Also, some of the bay­ous, such as Brays, can only han­dle 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.

Be­cause of big early 20th­cen­tury floods, Houston de­signed two dry emer­gency reser­voirs that are only ac­ti­vated in heavy rain, Ad­dicks and Barker, both formed by earthen dams. Ad­dicks is 11.7 miles long with a max­i­mum el­e­va­tion of nearly 123 feet. Barker is 13.6 miles long and has a max­i­mum el­e­va­tion of 114 feet.

Nor­mally the flood­gates are open and the two ar­eas are dry park­land with sports fields and bik­ing paths. They were essen­tially dry on Aug. 25, the day Harvey struck, East said. By the mid­dle of the next day, the flood­gates were closed and water lev­els were start­ing to rise, East said.

Now the reser­voirs are overflowing. Of­fi­cials are be­ing forced to re­lease some of the water press­ing against the 70-year-old dams and back­ing up into wealthy sub­di­vi­sions. But those re­leases could worsen the ex­treme flood­ing down­stream in Houston.


Water is re­leased from the Ad­dicks Reser­voir as flood­wa­ters rise from Trop­i­cal Storm Harvey on Tuesday in Houston.

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