In the continuing quest for understanding, today I googled “What are the most effective forms of flood mitigation?” The query returned 284 million results, including the one following.

A&M Study of Buffalo Bayou Found Stormwater Storage Most Effective

One interesting study co-authored by a Texas A&M professor, Samuel Brody, was titled, “How effective are drainage systems in mitigating flood losses?” This particular study compared the relative effectiveness several options and found:

• Storage-based drainage mechanisms are most effective for flood mitigation.
• 92% of flood damage cost can be saved by using storage-based facilities.
• Installing conveyance-based systems on property roads reduces flood damage by 19%.

The authors based their study on Buffalo Bayou and defined effectiveness as “flood-damage reduction.”

Expanding storage and conveyance are certainly the go-to solutions for Harris County Flood Control District (HCFCD). One former director of HCFCD told me that he agrees that storage is the most effective option in this area and that conveyance is also effective, but less so.

More Options on Menu…

But many more solutions exist.

I didn’t have time this morning to compare the other 284 million hits, so I asked ChatGPT my question. The AI bot replied:

“Flood mitigation involves various strategies and measures aimed at reducing the risk and impact of flooding on communities and infrastructure. Some of the most effective forms of flood mitigation include:

1. Floodplain Management: This involves regulating land use and development in flood-prone areas to minimize the exposure of people and property to flood risks. It may include zoning regulations, building codes, and restrictions on construction in flood-prone areas.
2. Natural Flood Management: Utilizing natural features such as wetlands, floodplains, and forests to absorb and slow down floodwaters. Restoring and preserving these natural features can help to reduce the severity of floods by increasing water retention and infiltration.
3. Flood Control Infrastructure: Building structures such as levees, dams, floodwalls, and stormwater drainage systems to control and redirect floodwaters. While these measures can be effective, they often come with high costs and potential environmental impacts.
4. Stormwater Management: Implementing practices to manage stormwater runoff, such as green roofs, permeable pavements, and rain gardens. These techniques help to reduce the volume and velocity of runoff, decreasing the risk of flooding.
5. Flood Warning Systems: Establishing early warning systems to alert residents and authorities of impending floods, allowing time for evacuation and implementation of emergency measures.
6. Elevation and Retrofitting: Elevating buildings and infrastructure in flood-prone areas to reduce their vulnerability to flooding. Retrofitting existing structures with flood-resistant materials and technologies can also help to minimize flood damage.
7. Community Education and Preparedness: Educating residents about flood risks, evacuation procedures, and emergency preparedness measures. Community involvement and awareness are essential for effective flood mitigation efforts.
8. Land Use Planning and Regulation: Implementing comprehensive land use plans that consider flood risk and incorporate measures to mitigate it. This may include avoiding development in high-risk areas and promoting sustainable land use practices.
9. Insurance and Financial Incentives: Encouraging the purchase of flood insurance and providing financial incentives for property owners to undertake flood mitigation measures such as elevating structures or installing flood barriers.
10. Cooperation and Coordination: Collaborating with neighboring areas to manage transboundary rivers and basins effectively.

“Effective flood mitigation often requires a combination of these strategies tailored to the specific geographic, social, and economic context of each region. Additionally, ongoing monitoring, evaluation, and adaptation of flood mitigation measures are essential to address evolving flood risks due to factors such as climate change and urbanization.”

The AI system didn’t quantify its answers, though, the way Brody’s study did and I can understand why. There is no one-size-fits-all answer.

Having researched approximately 2500 stories since Hurricane Harvey, I’ve written dozens of posts in each of the 10 categories above.

Some of the standouts include:

1. Floodplain Management: Remember the Romerica story? International developers wanted to build 50-story high rises in the floodplain and floodway of the San Jacinto West Fork…with no viable evacuation route. Thank goodness the Army Corps denied the permit.
2. Natural Floodplain Management: Remember the two Elm Grove floods in 2019? For years, before a developer clearcut 270 acres in the headwaters of Taylor Gully, the area below the new development remained flood free – even during Harvey. Clearcutting contributed to the flooding of hundreds of homes. Now we’re looking at expensive man-made fixes.
3. Floodwater Infrastructure: Stormwater detention basins and channel widening have proven effective almost everywhere in and around Harris County. They’re expensive, but proven solutions in our flat, low-lying area. But they only work in areas with room to build them. In older areas, they often require buying out entire neighborhoods.
4. Stormwater Management: The U.S. General Services Administration has found that green roofs have been found to reduce stormwater runoff by up to 65%.
5. Flood Warning Systems: One of the most memorable aspects of Harvey was how rising floodwaters caught people unaware in the middle of the night. Twelve people died in Kingwood Village Estates during emergency evacuations, when they could have driven out safely just hours earlier.
6. Elevation and Retrofitting: John Blount, former Harris County Engineer found that areas that adopted improved building codes after Allison had 20X less damage during Harvey.
7. Community Education and Preparedness: HCFCD’s Final Harvey Report found that more than 70,000 homes in Harris County flooded, which were outside of any known floodplain. Few people understand their true flood risk.
8. Land-Use Planning and Regulation: Even as I write this, new developments are being built in high-risk areas, such as Northpark South, where the entrance to the new subdivision was under 8 feet of water during Harvey. How soon we forget!
9. Insurance and Financial Incentives: Until recently, flood insurance was subsidized by the Federal Government. Some say that encouraged people to build in risky places. But FEMA’s new risk-based rates are encouraging people to be more cautious now about where they build and buy.
10. Cooperation and Coordination: In a widespread 100-year flood, more than 2 million acre feet of runoff funnel through the Lake Houston Area from more than 2800 square miles outside of Harris County. Floodwater does not respect political boundaries. We will not solve flooding alone.

There are no simple answers to “What are the most effective forms of flood mitigation?” But the areas outlined above offer good starting points for exploration.

Posted by Bob Rehak on 3/25/24

2400 Days since Hurricane Harvey