New Sand Mining BMPs needed to control sediment pollution.

In the years after Hurricane Harvey, I published more than 3,000 posts about flooding and flood mitigation. They contain about 2 million words – the equivalent of more than 25 average-length novels. That’s daunting for even the most dedicated readers.

So, this page summarizes the main lessons learned since then. They fall into three categories:

  • Generic factors that contribute to flooding
  • Partly generic factors amplified in the Lake Houston Area
  • Relatively distinctive factors in the Lake Houston Area, rarely found in combination elsewhere.

This “quick guide” can help educate readers and inform policy makers.

I wish to acknowledge the help of ChatGPT in summarizing those 2 million words. I also wish to acknowledge help from dozens of engineers, and elected and appointed officials leading the fight to reduce future flood risk.

I. UNIVERSAL (GENERIC) DRIVERS OF FLOODING

These show up in virtually every developed watershed in the U.S. and globally.

  1. Urbanization & Impervious Cover
    • The single most consistent, anthropogenic driver of flooding worldwide.
  2. Outdated Rainfall Assumptions
    • A systemic, engineering/design-lag problem.
  3. Floodplain Encroachment
    • A classic externality problem seen globally.
  4. Fragmented Governance
    • A structural governance issue, not hydrologically unique.
  5. Infrastructure Bottlenecks
    • A fundamental hydraulic constraint issue.
  6. Prevention vs. Recovery Funding Imbalance
    • An economic and policy pattern across the U.S.

II. PARTLY GENERIC, BUT AMPLIFIED IN LAKE HOUSTON

These exist elsewhere but are more intense, more frequent, or more consequential in the Lake Houston Area.

  1. Detention Limitations at Scale
    • Site-by-site detention doesn’t account for cumulative watershed effects
  2. Reservoir Operations & Coordination
    • Multi-reservoir systems require coordination, but construction and management differences make that difficult in the Lake Houston Area,
  3. Flat Terrain
    • Low gradients and backwater effects contribute to large water surface increases across wide areas
  4. Subsidence
    • Rapid population growth is leading to aquifer depletion that causes subsidence, increasing flood risk.

III. RELATIVELY DISTINCTIVE TO LAKE HOUSTON (OR RARE IN COMBINATION)

  1. Role of Industrial-Scale Sand Mining in Lake Houston Area Flooding
    • Few urban areas have such dense clusters of sand mines directly upstream in floodways.
  2. How Sediment-Induced Loss of River Conveyance Increases Flood Risk
    • Several factors reinforce each other and make the threat especially potent in the Lake Houston Area.
  3. Terminal Reservoir with Limited Gate Capacity
    • How placement and construction of the Lake Houston Dam concentrate flood risk
  4. Extreme Upstream Growth in Flatland With Constrained Drainage
    • Drainage funnels into a relatively constrained downstream system over flat land
  5. The “Stacking Effect” and How it Erodes Margins of Safety
    • A system where runoff is increasing, conveyance is decreasing, and control is fragmented—all at the same time.

Put ’em all together and it’s like spinning the Wheel of Misfortune.

Wheel of Misfortune
Image created by ChatGPT from the key points in the outline above.

Other Posts That Offer Key Lessons

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