Stormwater Tunnel on Buffalo Bayou Will Not Prevent Flooding

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Please note that the Houston Chronicle has published a highly useful explanation of the coastal protection plan for Galveston Bay known as the Ike Dike. Unfortunately the paper has not figured out how to market to nonsubscribers.

Oct. 2, 2022

Large stormwater tunnels will likely not prevent flooding on Buffalo Bayou, according to the recent report from the Harris County Flood Control District.

Tunnels draining the federal flood control dams on upper Buffalo Bayou would not even be adequate to prevent a catastrophic overtopping of the dams or flooding of properties behind the reservoirs if a Harvey-like storm parked on top of the reservoirs, according to an engineering analysis prepared for Houston Stronger, a west Houston-based group formed in the wake of Harvey in 2017.

The Harris County Flood Control District is considering a $30 billion, 133-mile system of eight large-diameter stormwater tunnels to manage flood risk in the county. The district issued its Phase 2 feasibility report at the end of March and updated it in September. The district has been holding public meetings and taking public comments in preparation for the next phase of analysis to begin in the spring.

Proposed route of the Buffalo Bayou tunnel, including tunnels draining Addicks and Barker reservoirs. From the Phase 2 report, p. 82.

Limited Capacity

The probability that the proposed Buffalo Bayou tunnel would not prevent flooding downstream on the bayou is based on its limited capacity. The main tunnel would connect to two short 40-foot diameter tunnels, less than two miles long, draining Addicks and Barker dams far upstream. They would have a combined capacity of 11,600 cubic feet per second (cfs). This would drain into the much longer 40-foot diameter bayou tunnel which would have a capacity of only 12,240 cubic feet per second. Inlets or intakes draining the entire bayou downstream would have to be closed to accommodate stormwater flowing into the main tunnel from the two dams. The main tunnel would traverse the city deep underground for some 22 miles all the way to the ship channel east of downtown. (p. 127) (See also p. 1130)

That means that Buffalo Bayou would still flood because the bayou floods from urban rain runoff below the dams even when the dam floodgates are closed and no stormwater is draining out of the reservoirs. (See also here.)

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6 thoughts on “Stormwater Tunnel on Buffalo Bayou Will Not Prevent Flooding”

  1. Keiji Asakura says:

    It is an expensive idea that seems to take away the resources needed to balance our overall region’s storm water resiliency.

  2. Brady Mora says:

    The outflow of these tunnels I find most concerning. As you say, what happens if high water blocks the outflow at the end of these tunnels, which certainly will happen during storm surge. In fact these tunnel gates will be blocked by floating debris and rendered inoperable on both ends. The sediment question is a valid one.

    Concentrated outflow from the drains of these tunnels will increase turbidity downstream causing erosion and river bank collapse. Forest cover on the bank will fall into the stream creating blockage. The serpentine nature of a natural gulf coast river or stream bank is a sediment deposition device that is engineered by the hand of God to distribute sediment when the water resides equally where it is needed to fill in low spots. This accommodates natural drainage.

    The politics of grass is what I am seeing. Tall native grasses are designed to recycle falling rain back into the atmosphere through a process known as evapotranspiration. This one word is the answer to our flooding problem. When we learn to harness the amazing power of the sun to make runoff slow down, through evapotranspiration, by covering the land in native tall grasses then nature will provide the solution.

  3. Sharon Nesteroff says:

    No tunnel .. aim higher aim perfect aim natural resource habitation aim safety and aim renewal to our nature .. without it you have nothing. Work with nature to provide for nature to help habitats, animals, birds, reptiles (non poisonous snakes), and insects and fish. We are to help nature not ruin it. It cannot be replaced! Plant milk weeds and vegetation .. provide water pools and water for wildlife to drink.
    Thank you.

    Houstonian Sharon Snyder Nesteroff. It is God’s nature, for man to help with. Know Jesus!

  4. Shelly Richardson says:

    So many streams and creeks flow into Buffalo Bayou, which flows into Galveston Bay and when we have High Tide the drainage pushes back and nothing will help. This is what happened during Harvey. I always watch the tide timeline and was amazed when Low Tide hit that afternoon.

    Keep track of our Magnetic Field!


    Shelly Richardson

  5. Jimmy Dunne says:

    Storm tunnels are too expensive to build. Best to just widen Buffalo Bayou so it will hold more water and move it faster to the Gulf of Mexico.

    Jimmy Dunne

    1. Widening rivers is like building bigger freeways: it just creates more traffic. The focus needs to be on stopping stormwater before it floods the stream. There are many other reasons that widening streams for flood management is a bad idea. Rivers, including the bayou, have a dynamic shape and form that adjusts to the flow as necessary. Overwidening the channel for a rare high flow event will cause the banks to collapse, requiring constant, costly, and environmentally damaging dredging and maintenance — which is what Flood Control has to do on the many other channels that have been “improved.” Furthermore, channelizing streams to increase the flow and velocity causes flooding downstream. Flood mitigation around the world focuses on slowing the flow.

      Aside from that, in the case of Buffalo Bayou, the upper banks are mostly privately owned. The land would have to be purchased at great expense.

      The irony is that where the bayou is naturally widening and deepening, our public agencies claim that widening and deepening is bad and needs to be stopped and fixed. But when they propose to deepen and widen our streams artificially at great cost (and significant profit to engineers), that’s good.

      Widening the river’s natural floodplain, however, is normally a good idea to help absorb overflowing floodwaters and move people out of harm’s way.

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