Overflow Spillways: Simple Idea to Help Keep Street Flooding Out of Homes

Overflow spillways in could have prevented many homes from flooding in May and again in September. Rain came down so fast in some neighborhoods that it couldn’t get through storm drains and into drainage ditches fast enough. Water backed up and flooded homes. I’m not talking about flooding like Elm Grove experienced from an external source. I’m talking about situations like we had in Mills Branch where approximately 25 homes flooded. They flooded, says the resident, when water backed up in the street, not because Taylor Gully overflowed.

Now Required in New Neighborhoods

Over the weekend, I corresponded with a Mills Branch resident who has anguished over what to do for months. In some cases, but not all, there may be a simple, relatively low-cost answer for the whole neighborhood. Overflow spillways. And Mills Branch might be a perfect candidate.

Matt Zeve, Deputy Executive Director of Harris County Flood Control, pointed out that regulations in newer neighborhoods now require, where applicable, overflow spillways.

How Overflow Spillways Work

These work for neighborhoods adjacent to drainage ditches, streams or bayous. The channel is built at an elevation that retains water in the street during heavy storms, but lets it flow out before it reaches the level of homes. Obviously, the street must slope toward the spillway. This wouldn’t work for homes in the middle of a block that formed a natural bowl. But assuming conditions are right…

Can Be Retrofitted to Older Neighborhoods

I asked Zeve if the Flood Control District could retrofit this concept to older neighborhoods. The answer: YES, if there’s a home between the neighborhood and the ditch that can be bought out to create space for the spillway AND if that home has flooded repeatedly.

Here are some pictures of the overflow relief spillways in place. The first goes into a retention pond.

The second goes into some woods that apparently contain a natural drainage channel.

Zeve says the Flood Control District has been buying homes and converting them to overflow spillways in key areas around the County.  These homes are in the lowest points and have flooded repeatedly.

Posted by Bob Rehak 1/6/2020, with thanks to Harris County Flood Control

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