Study: ‘Third Reservoir’ Won’t Stop Flooding in Northwest Harris County

 

 

By Nick Powell, Houston Chronicle, May 10, 2019

A long-discussed idea for a third reservoir to prevent extreme Hurricane Harvey-level flooding in beleaguered neighborhoods along Cypress Creek might not be the flood mitigation panacea it was conceived as, according to a Rice University study.

After tens of thousands of homes flooded in the watersheds of Cypress Creek and the Addicks and Barker reservoirs during Harvey in 2017, regional planners revived an idea originally conceived nearly 80 years ago by the U.S. Army Corps of Engineers — a third reservoir to supplement the capacity of Addicks and Barker in the event of a major flood.

But the study by Rice University’s Severe Storm Prediction, Education, and Evacuation from Disasters (SSPEED) Center revealed the difficulties in attempting to eliminate flooding in the Cypress Creek watershed, which covers over 300 square miles in northwest Harris County and features over 250 miles of open streams.

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The study also concluded that the remaining undeveloped land in the Cypress Creek area should be protected against development, specifically the Katy Prairie west of Houston, where vegetation and wetlands provide flood protection.

Harris County Commissioner Jack Cagle, whose northwest Harris County precinct includes areas likely to be affected by any future flood mitigation effort, believes that prairie land could be a significant component of a future reservoir.

Read the rest of this article in the Houston Chronicle.

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The Greater Houston Flood Mitigation Consortium is holding a free public event, Tuesday, May 14, from 3:30 to 6 p.m. at Rice University’s Bioscience Research Collaborative, 6500 Main Street, to present the findings from the Cypress Creek study as well as other recent research and reports.

Reducing Flooding on Buffalo Bayou

Corps Studying the Issue. Public Comments Due by May 31.

Last Public Meeting Tonight

 

May 9, 2019

The Corps of Engineers is studying ways of reducing flooding along Buffalo Bayou and its many tributaries, including upstream and downstream of Addicks and Barker dams in west Houston, as well as the federal dams themselves.

The Corps’ Galveston District has been conducting a series of public meetings explaining possible approaches to reducing flood risk and seeking public comment. The last public meeting is tonight, May 9, from 6 to 9 at the Cypress Ridge High School, 7900 N. Eldridge Parkway. But the public comment period doesn’t end until May 31.

Here is a link to the Corps’ presentation at the meetings. Here is a link to the storyboards presented at the meetings.

And here is the email address for asking questions and sending in your comments and suggestions about what the Corps and the Harris County Flood Control District (and Fort Bend County) should be doing about flooding. Note that this does not include what the City of Houston could or should do.

The three primary problems being addressed by the Corps are:

  • Flooding downstream of the reservoirs on Buffalo Bayou
  • Performance and risk issues related to flow around and over the uncontrolled spillways
  • Flooding upstream of the reservoirs

The various suggested approaches are heavy on big engineering projects like flood tunnels, bypasses, new dams and reservoirs, increasing the storage capacity of the reservoirs, and “channel improvements” along Buffalo Bayou and other streams flowing into it.

But the alternatives also include floodproofing, better warning systems, signage, and public education; stormwater detention, and “property acquisition,” which could mean buyouts of flood-prone properties as well as preservation of forest and prairie, which help slow and absorb rainwater.

Save Buffalo Bayou is in favor of stopping and slowing stormwater runoff before it floods our bayous and streams. This is modern floodplain management. That means more trees and greenspace, more wetlands and prairies, more detention in neighborhoods and shopping malls, more permeable surface. Focusing on collecting and conveying more stormwater faster—and destroying our natural landscape and drainage system in order to do it—only leads to more flooding. Dredging, deepening, and widening the bayou and other streams only leads to bank collapse, constant maintenance and repair, and more flooding.  (See here and here and here.) It’s like building bigger freeways: it doesn’t work.

Another problem with hard structures: They don’t move. Nature does.

Preserving old stands of trees, natural swales, wetlands, oxbows, vegetated riparian areas, and meanders; building small weirs, sediment structures, wet gardens, and setback levees; lengthening streams, and accepting large woody debris in the channel are useful techniques. Using these practices to work with the natural motion of the river is more effective – and less expensive – in reducing flood damage and helping us realize benefits from the water.

Floodplain Management: A New Approach for a New Era, p. 137

 

Image courtesy of the Galveston District, Corps of Engineers

 

 

 

 

 

They’ve Done It. For No Good Reason

Flood Control Destroys Forest on Buffalo Bayou

 

May 6, 2019

(Updated May 7, 2019, with clarification from Harris County Flood Control.)

They’ve done it. Last week the Harris County Flood Control District began knocking down towering sycamores and pines in one of the last remaining forested areas open to the public on Buffalo Bayou.

This tree-cutting is not new. The Flood Control District has been razing forest next to streams all over the county for decades, mainly to excavate floodwater detention basins. Slowing down, holding back rainwater runoff is a good idea. But trees do that. And more. Flood Control is damaging the environment, destroying the limited access we have to nature in the city, while doing little to reduce flooding. Possibly even making it worse.

Their private consultants don’t consider the benefits of trees when they spend millions of taxpayer dollars on flood studies and plans. And there are significant benefits, including flood protection.

 

Because Leaving Trees in Place is Not a “Project”

The problem is, as the Federal Emergency Management Agency (FEMA) points out (see pp. 7-9), leaving trees in place—nature-based flood risk reduction—is not considered a “project.” There is a political bias in favor of costly, large-scale structural approaches, despite the obvious advantages to small-scale, non-structural, green or natural approaches to flood management. (Although in this case, they seem to be doing the project because it’s “cheap and easy.”)

Trees cleared on the south bank of upper Buffalo Bayou in Terry Hershey Park. Trees were cleared on the north bank in the Nineties. Photo by SC May 5, 2019

 

“Protection of a natural channel and adjacent river corridor, floodplain or wetland often does not meet the conventional concept of a ‘project,’” notes FEMA.

The District needs “projects” in order to look like it’s doing something, especially after county voters approved $2.5 billion in bonds for flood reduction “projects.” And contractors don’t make money from not doing or not designing “projects.”

Other factors preventing more enlightened, more effective flood management include the lack of multidisciplinary expertise, leading to a dependency on old, traditional, and familiar engineering approaches, points out FEMA.

Like spending millions repairing the channelized banks of the bayou in Terry Hershey Park where the straightened stream is attempting to restore its natural meanders. Allowing the bayou to recover its bends, thus lengthening itself, would increase its capacity naturally and for free. (p. 11)

 

Because That’s What They Always Planned to Do

The trees recently downed by Flood Control were on the south bank of upper Buffalo Bayou in Terry Hershey Park, a semi-wild wooded area beloved by hikers and bikers. The 500-acre rolling linear park runs for some six miles on both sides of the bayou below Addicks and Barker dams in west Houston.

Read the rest of this post.