Why Houston Floods, According to Flood Control

It Rains a Lot! What Can Flood Control Do?

March 3, 2024

For years the Harris County Flood Control District has been giving public presentations that include a slide purporting to explain “Why is Harris County Flood Prone.”

According to Flood Control, the reasons Harris County floods are:

  1. It rains a lot.
  2. The landscape is flat.
  3. Soil doesn’t soak up the rain fast enough.

Strangely missing from this list is arguably the number one cause of flooding in our city: it’s covered in concrete, asphalt, and roofs, otherwise known as impervious surface. (p. 182-183) That means artificial hard stuff that doesn’t allow the rain to soak into the ground but instead increases runoff, sending stormwater really fast into our streets and overwhelming our drainage systems, natural and built. The built city also absorbs a lot of heat, influencing rain patterns, among other problems. (See “Cities Depaving for a Cooler Future.”)

Here are a few further references for the role of impervious surface in Houston’s flooding:

Buildings Partly to Blame

More Pavement, More Problems

Houston’s Urban Sprawl Increased Rainfall, Flooding During Hurricane Harvey

Houston’s Flood is a Design Problem

What Causes Floods

The Rapid Urbanization of Houston: How It Happened and Why It Matters

Why Not Mention Impervious Surface?

We asked Flood Control why their explanation doesn’t include impervious surface. A representative graciously responded:

“You are correct that impervious surfaces are a cause of flooding in our area. However, in our ‘Why is Harris County Flood Prone’ slide we are focusing primarily on the sources of flooding that our capital and maintenance projects can directly address. As you know the Flood Control District does not have regulatory authority over development and the amount of impervious surface added each year.”

Well, true. But the slide is about the reasons Harris County floods, not what Flood Control can do about it. And the flood control district doesn’t have authority over rainfall or the topography or soil type either.

But what about Flood Control’s claim that the landscape is flat and covered in “clay soils that do not soak up excess rainfall quickly”? Actually since most of it is covered in impervious surface, these points would almost seem irrelevant. But they are also not exactly true.

Is the Houston Region Really Flat? Not So Much

A 2022 study from the University of Texas confirmed what anyone who grew up around here already knows: the seemingly flat landscape is in fact sculpted with numerous sloping hills carved out by the many branching channels, otherwise known as gullies or creeks, that feed into our major streams, such as Buffalo Bayou.

Read the rest of this post.

A creek flowing towards Buffalo Bayou through a deep, wide gully in Houston’s Memorial Park. Photo Feb. 19, 2024, by SC

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