9/16/2026 – In my previous post, I summarized causes of flooding. I grouped 83 contributing factors into three main categories: nature, things humans do, and things humans fail to do. In my continuing effort to summarize years of research, today, I would like to summarize major categories of flood-mitigation solutions.

Major Categories of Flood-Mitigation Solutions

Flood mitigation is fundamentally about managing water better and reducing human vulnerability as development expands throughout watersheds. Below, I have grouped solutions into several major categories to make them easier to comprehend and remember. Each category lists multiple specific solutions within it that I have previously posted about.

1. Reduce runoff at the source

Keep rainfall from quickly becoming runoff. Preserve forests and natural areas. Limit unnecessary impervious cover with green alternatives, such as permeable pavement, rain gardens, bio-swales, green roofs, soil restoration, infiltration practices, and development standards that control post-development runoff.

While particularly useful for moderate storms, during extreme events, soils and small-scale storage can easily become saturated. So, view them as one layer of protection.

2. Preserve natural storage

This is almost always cheaper than trying to recreate storage after development.

Protect floodplains, wetlands, natural depressions, riparian corridors and other areas where water can temporarily spread without causing substantial damage.

The fundamental principle is:

Don’t eliminate storage you will later have to replace with expensive engineered storage.

3. Detain or retain excess runoff

Where development has already increased runoff, temporarily store the excess.

Solutions include detention basins, regional detention facilities, retention ponds, wetlands, underground storage and flood-control reservoirs. But don’t evaluate storage solely by acre-feet. Its location, outlet capacity and release timing also matter. A detention basin that releases water at the wrong time can contribute to downstream peaks.

4. Improve conveyance

Once water enters the drainage network, there must be enough capacity to move it safely.

Solutions include larger storm sewers, additional inlets, larger culverts, bridge modifications, ditch improvements, channel widening, selective channel excavation, bypass channels, diversion channels, flood tunnels and—in appropriate circumstances—dredging.

But there’s an important caveat:

Moving water faster isn’t necessarily flood mitigation if the receiving system cannot handle it.

Improving conveyance upstream without considering downstream capacity can simply transfer the flood problem downstream.

5. Remove bottlenecks

The weakest link in a drainage system limits the entire system’s effectiveness.

A watershed may have ample channel capacity except for one undersized bridge, culvert, railroad crossing, utility crossing, sediment deposit or other constriction. This is especially important in an area, such as Houston, with flat terrain.

6. Manage sediment

Sediment management is especially relevant to the San Jacinto/Lake Houston system.

Possible mitigation measures include erosion prevention, construction-site BMP enforcement, stream-bank stabilization, better sand-mining practices, setbacks from channels, protection against pit capture, sediment traps where appropriate, dredging, and maintaining critical channel and tributary-mouth conveyance.

The objective: prevent excessive human-caused sedimentation from reducing critical conveyance or storage.

7. Manage flood peaks better

When water arrives affects flood peaks as much as how much arrives.

Potential solutions include coordinated reservoir operations, coordinated detention releases, strategically located regional detention, watershed-scale hydrologic modeling, real-time rainfall/stream monitoring, forecast-informed operations and—in some circumstances—pre-releases.

The goal: to avoid peaks from multiple tributaries, detention systems and reservoirs arriving at the same location at approximately the same time and stacking on each other.

8. Protect structures

Where development already exists in locations that have become hazardous, take steps to protect structures.

Examples include home elevation, floodproofing, floodwalls, levees, berms, gates, pumps, backflow prevention, elevated utilities and protection of critical facilities.

These measures generally reduce damage rather than eliminate flooding. But understand that a levee or floodwall, like the one at Kingwood High School, can reduce risk without making the protected area flood-proof.

9. Remove development from and/or stop developing in the highest-risk locations

Sometimes the most durable flood-control is simply to stop putting valuable things where water wants to go repeatedly.

Measures include voluntary buyouts, property acquisition, conversion of repetitive-loss areas to open space, preventing redevelopment of acquired properties, stricter floodway development restrictions, and avoiding new critical facilities in flood-prone areas.

This attacks exposure rather than hydraulics. But it protects people and property. Local examples include the buyout of townhomes in Forest Cove and efforts to block the proposed development of homes where Cypress, Spring and Turkey Creeks join the San Jacinto West Fork.

10. Maintain the drainage system

Maintenance is one of the least glamorous and most important mitigation strategies.

Maintain channels, storm sewers, inlets, culverts, detention basins, pumps, gates and outfalls; remove debris and problematic sediment; repair erosion; inspect infrastructure; and preserve the designed storage and conveyance capacity.

A drainage system’s capacity should not be considered fixed at the capacity it had when constructed.

Without maintenance, design capacity deteriorates and flood risk increases.

11. Enforce the rules already on the books

New regulations accomplish little if existing ones aren’t enforced.

That includes floodplain/floodway restrictions, detention requirements, no-net-fill requirements, construction BMPs, stormwater permits, wetland requirements, mining permits, drainage easements and development conditions.

Effective enforcement goes beyond permitting. It requires inspection, documentation and correction when violations occur.

12. Design for tomorrow’s watershed

Flood infrastructure often lasts many decades. Designing only for today’s watershed can lock in future problems.

Planning should consider growth of impervious cover, upstream development, updated rainfall probabilities, subsidence, land-use change, downstream constraints and reasonably foreseeable changes in watershed hydrology.

This means building in generous safety margins. Development projects should do more than meet minimum requirements. They should still keep residents safe as the watershed develops.

13. Coordinate across the river basin

Floodwaters don’t recognize municipal or county boundaries. Effective mitigation therefore requires shared rainfall assumptions, compatible design standards, watershed-wide models, coordinated detention, reservoir operations, development assumptions, sediment management and capital planning.

It also requires a single accountable authority to “own” problems. Otherwise one jurisdiction’s successful drainage project can become another jurisdiction’s increased inflow.

14. Improve forecasting, warning and preparedness

These actions don’t prevent flooding. But they can dramatically reduce its consequences…as we learned in the Hill Country flooding at Camp Mystic.

Better rainfall forecasts, stream gauges, reservoir gauges, inundation forecasts, warning systems, evacuation planning, emergency communications and public education can save lives and property.

Posted by Bob Rehak on 9/16/26

3305 Days since Hurricane Harvey