Houston Too Flat, Soil Too Impenetrable?

Flood Control Planning Director Claims Natural Flood Management Can’t Be Done Here

Advocates Call BS

So Is Flood Control District Working in Our Best Interests?

Sept. 29, 2021

The virtual workshop was all about nature-based flood management (trees, vegetation, greenspace, prairies, wetlands, native gardens), about the value of protecting and restoring floodplains and natural areas, why this green approach costs less, is more effective, resilient and flexible, reduces the long-term risk of catastrophic failure, and adds economic value to communities, not to mention health and environmental benefits.

There were related topics: stopping stormwater where it falls, buying out properties in floodplains, not building in floodways, elevating homes, and how protecting floodplains and green areas reduces the cost of flood insurance, among other things.

But then came the long-time planning director of Harris County Flood Control who all but laughed at the idea of nature-based flood management. Harris County is covered in “impermeable clay soils,” he said.

It’s a common refrain from naysayers, including the leaders of Flood Control, who claim prairies, rain gardens and green infrastructure can’t work here because the land is basically as flat and impenetrable as concrete. Local landscape architects, hydrologists, environmentalists, and others have encountered this obstinacy for years. “Nonsense” and “bs” are typical off-the-record responses.

The obvious conclusion, if you follow the logic of Flood Control: we have to keep doing costly engineering projects, hand out more lucrative contracts, bulldoze and dredge and deepen and widen our streams. And then hand out more contracts to do it all over again. Because that’s what Flood Control does: projects and contracts.

Never mind how bulldozing, dredging, etc. compacts the soil and makes it less absorbent, killing all the healthy, useful organisms in the banks and bed, and increases flooding and erosion. (See also here.) It’s more lucrative (for somebody) to keep tearing down and developing the forests and prairies, though ultimately it costs the taxpayers more. Fill our flowing streams as fast as possible, flood our neighborhoods upstream and downstream – because, according to Flood Control, the natural landscape is no different from concrete and rooftops anyway.

But It’s Not True

But is it true? No.

In fact, most of the soil in Harris County is moderately highly absorbent to very highly absorbent. Furthermore, plant roots help facilitate the infiltration of rain where the soil is less absorbent, especially if we let the grass grow higher and plant native plants.

At a recent education program for local officials sponsored by Texas A&M, Ataul Hannan, director of planning for Flood Control, showed a photo of downtown Houston during the infamous 1935 flood. He said that the Katy Prairie, which once extended from the edge of the Spring Creek forest northwest of the city south to beyond forested Clear Creek in the southeast, was undeveloped at the time. (Apparently meaning that it wasn’t covered in houses, shopping centers, and roads because the prairie then was already ranch and farmland.)

Said Hannan: If the prairie was all that great at slowing or storing stormwater back in 1935, why did downtown Houston flood?

And the correct answer, as determined by the Texas State legislature in 1937, is that a narrow, badly designed bridge blocked the flow of stormwater from Buffalo and White Oak bayous and caused it to back up and flood downtown Houston in 1935. (See our report here.)

Nevertheless, the state legislature in 1937 authorized the establishment of the Harris County Flood Control District to aid the US Army Corps of Engineers in stripping the forests, straightening the meanders, and covering our once-beautiful major streams in concrete. (Never mind that the enabling legislation also charged Flood Control with the “conservation of forests.”)

It was a disastrous policy that has only increased flooding, damaged our water quality, destroyed our natural environment, and created the need for costly, continuing maintenance. (See Brays Bayou, a joint channelization project which began in the mid-1950’s and now, after more than seventy years of increasing flooding and hundreds of millions of public dollars, they are almost done.)

The 1929 and 1935 floods also prompted the Corps of Engineers to construct Addicks and Barker dams on the Katy Prairie, which encouraged development of the prairie (still happening) and people and businesses to move into the floodplains, believing they were safe. This has led to the current problems we now have upstream and downstream of those dams. (See here and here and here.)

Operating in a Narrow Channel

The Corps of Engineers has been evolving, somewhat abandoning its earlier counterproductive practices, even going so far as to restore streams that it destroyed decades ago. But the Harris County Flood Control District, though also focusing on stormwater detention projects with more or less natural features (often involving the removal of trees), remains addicted to stripping, grading, dredging, widening, and even straightening streams in the name of “improving conveyance” or “restoring design capacity.” This despite the fact that all of these practices have been shown to increase flooding, damage the natural functioning of the stream, and require continued, costly maintenance. (Here and p. 36)

As one example of the district’s outdated and counterproductive approach, a project that would seem in violation of the county’s Harris Thrives Resolution (see below), the district is bulldozing ahead with a $295 million “channel rectification” project along fifteen miles of Clear Creek, plus miles of “improvements” along three tributaries, Turkey Creek, Mud Gully, and Mary’s Creek  (p. 58 plus map here). Unfortunately this is being done in collaboration with the Galveston District of the Corps of Engineers. According to one distraught longtime Friendswood resident, the project involves the removal of numerous century-old oaks and pines and other native vegetation along the winding stream.

Here and here are some other examples of Flood Control’s failing, outdated, and even contradictory approach to flood risk management.

Too Flat for Drainage?

Flood Control’s Hannan also quoted an 1880 federal agricultural report on the Houston region. “The surface of the entire region is very level and even, with a descent to the coast so gradual as to afford no drainage to the soils, and, as a natural consequence, water remains in pools upon the prairies of the region until removed by evaporation,” wrote a Mr. R.H. Loughridge, special agent, in his report on Texas cotton production to the Census Office.

So Mr. Loughridge found that the prairie actually holds and detains stormwater, a useful thing. Unlike concrete.

But does it drain, or evaporate, or soak into the ground?

The Harris County Flood Control District knows that the prairie drains. For example, during large storms Cypress Creek in Waller County to the northwest overflows and drains to the southeast over land and into streams and eventually into Addicks Reservoir in Harris County, a problem well-known to the district.

So there is some tilt to the land. Most of our creeks and streams flow west to east if not north to south. And there are hills and slopes in the terrain around these streams and gullies, if they haven’t been buried or filled and paved over by developers.

And as for rainfall soaking into the prairie, the value of deep-rooted native plants has been much documented, even by Harris County Flood Control. See the above-mentioned Cypress Creek Overflow Report, which lauded the flood storage capacity of prairies and the infiltration benefits of prairie grass root systems. (pp. 872-873).

For another example, check out what this 2002 master plan for Buffalo Bayou says about our prairies. It describes “plants with roots that extend six to eight feet deep. These deep-rooted plants capture and infiltrate much of this region’s high rainfall amounts. With an infiltration capability of several inches of rain per hour, it is likely that these prairie grass complexes once absorbed much of the water that fell on them.” (pp. 120-121)

And here is another report on the absorption capacity of the Katy Prairie from the Greater Houston Flood Mitigation Consortium (see pp. 13-14 and 22).

Of course, these tall grasses also store carbon. So there’s that too.

All good reasons to protect and restore native prairies and plant native plants in your yard.

Is Flood Control Working in Our Best Interests? Whose Best Interests?

Hannan’s comments come at a time of increasing official acknowledgement that we cannot engineer our way out of floods. Even the Corps of Engineers is promoting “engineering with nature.” In fact, shortly after the workshop with Hannan, the Corps co-sponsored a virtual launch of the International Guidelines on Nature and Nature-Based Features for Flood Management. The launch featured representatives from the UK and the Netherlands, in addition to officials with the National Oceanic and Atmospheric Administration, the Corps, the World Wildlife Fund, The Nature Conservancy, the World Bank, and others.  

The City of Houston and Harris County both emphasize green infrastructure, at least in principle. In 2019 Harris County Commissioners Court passed the “Harris Thrives” resolution that, among other things, instructed the Flood Control District to “emphasize an approach that respects, reclaims, and restores floodplains; preserves undeveloped prairies and forests that detain stormwater; and encourages the use of nature-based solutions, natural infrastructure, and cutting-edge technological methods where possible in public and private projects …”

The City of Houston adopted its Resilient Houston plan in February 2020, based largely on a Living with Water report issued in January 2020. Among the guiding principles in the report are “hold water where it falls,” “make space for bayous,” and “bring back the prairie.” (p. 21)

In March 2021 the City followed up with a one-year report on how well the city was doing achieving goals outlined in the Resilient Houston plan. Among those goals were plant millions of native trees, remove habitable structures from the floodway, conserve 24 percent of undeveloped regional lands as natural spaces, make room for water, respect bayous and natural floodplains, and integrate green stormwater infrastructure. (pp. 20-23)

Note that insurance premiums for the National Flood Insurance Program are based on how well a community protects the natural functions of floodplains along streams, including wetlands and prairies and open space, both public and private. (A topic at the virtual workshop at which Hannah spoke in early September.) These numerous benefits, as described by the Federal Emergency Management Agency and the Association of State Floodplain Managers, include slowing and absorbing runoff, storing and cleansing stormwater, reducing sediment, promoting groundwater and aquifer recharge, wildlife habitat and human enjoyment.

The virtual meeting featuring Hannan was called “Community Planning for Flood Mitigation,” a curriculum offered by Texas Citizen planner, a planning education program for local officials created by Texas Watershed Partners, a program of Texas A&M AgriLife Extension Service.

No one claims that nature-based flood management alone can save us. But there is increasing acceptance of the fact, formally proposed some 80 years ago by the great Gilbert White, that modifying human behavior (not moving into floodplains, for example) is a better approach, and that structural (engineered) solutions only make flood hazards worse.

SC

Donate! Donate! Donate! Donate!

Please donate to Save Buffalo Bayou. Our work needs your support. We don’t usually ask but we should have been asking. We are very much in need of individual contributions. No gift is too small! All donations are tax-deductible.