Chapter Five: Mitigating Flood Damage

Introduction

As communities continue to face rising flood risks due to climate change, selecting the right flood mitigation strategies becomes increasingly important. Both residential and non-residential sectors require effective solutions to minimize the damage caused by flooding, but their needs and priorities often differ. While residential areas may focus on protecting homes and maintaining livable conditions, commercial areas prioritize safeguarding businesses and infrastructure critical for economic activity.

Mitigation is defined as any action taken to reduce the loss of life and property by lessening the impact of disasters. Mitigation can be done at the individual level (e.g., implementing individual building protection, purchasing flood insurance, etc.), at the neighborhood level (e.g., developing green infrastructure projects, drainage projects, etc.), at the community level (e.g., enforcing higher regulatory standards, implementing large scale drainage projects, participating in the Community Rating System, etc.), and at the state level (e.g., adopting strong building codes).

Flood Mitigation Options for Residential Structures

Homeowners and local governments can employ a range of basic flood mitigation measures to protect residential areas. The most effective strategies often combine structural and non-structural solutions, tailored to local conditions and risk levels. One of the most common flood mitigation techniques is to elevate a building above the anticipated flood level. This approach can significantly reduce flood damage by lifting the living spaces and utilities above the reach of floodwaters. While elevation is particularly effective in areas with frequent or severe flooding, it can be costly and challenging to implement in densely populated neighborhoods. Additionally, elevating existing structures may be less feasible than incorporating elevated designs into new construction.

Constructing small retaining walls, levees, or berms around individual homes or neighborhoods can provide temporary protection from flooding. These barriers can redirect water away from structures, but they are not floodproof, as they may be overtopped or eroded by powerful floodwaters. Moreover, barriers can alter natural drainage patterns, potentially increasing flood risk in other areas.

Green infrastructure uses natural features like swales, rain gardens, and permeable surfaces to absorb and slow down stormwater runoff, reducing the amount of water reaching vulnerable areas. Such measures help improve the overall resilience of residential neighborhoods by not only reducing flood risk but also enhancing local ecosystems. The challenges with green infrastructure include the availability of space in urban areas and the need for ongoing maintenance.

Flood Mitigation Options for Non-Residential Structures

For non-residential structures, flood mitigation strategies focus on protecting business and public facilities and ensuring that infrastructure remains functional during and after flooding events. The primary goal is to reduce downtime and minimize the economic losses associated with floods. Effective flood mitigation for non-residential structures often involves a combination of structural measures, non-structural measures, and planning strategies to address specific risks and vulnerabilities.

Dry floodproofing involves sealing a building’s exterior walls, doors, and windows to prevent floodwaters from entering. This technique can be effective for protecting residential structures against shallow flooding, but it may not be suitable for locations where water levels rise rapidly or reach significant depths. The method often requires ongoing maintenance to ensure waterproof seals remain intact and may involve higher initial costs for retrofitting existing buildings.

One effective approach is elevating critical infrastructure, such as electrical equipment and backup generators, above anticipated flood levels to prevent damage. This method is more straightforward for new constructions, while retrofitting existing buildings can present logistical challenges. Another strategy is wet floodproofing, which allows floodwaters to enter a building in a controlled manner, equalizing pressure and minimizing structural damage. This technique can be effective for non-critical spaces but may not be suitable for areas prone to prolonged exposure to water. Additionally, commercial properties can use temporary or permanent flood barriers and shields to protect vulnerable points like entrances and windows. While these barriers require regular maintenance, they provide robust protection against flooding when properly implemented. Improving drainage systems around commercial properties is another critical strategy, as it enhances the area’s ability to manage runoff and prevents water accumulation. Finally, non-structural measures, such as purchasing flood insurance and developing comprehensive business continuity plans, are essential for protecting commercial properties. These strategies enable businesses to recover quickly and maintain operational stability in the aftermath of flooding events.

Levels of Mitigation

Property owners can take steps to mitigate flood damage.

• Individual homes or businesses: elevation, wet and dry floodproofing; nature based solutions (green infrastructure); acquisition/ buyout, relocation, insurance
• Neighborhood: drainage projects; nature based solutions (green infrastructure), buyout, relocation
• Community wide: land-use, higher regulatory standards (freeboard, no fill),CRS, education and outreach, , nature based solutions (green infrastructure), flood warning systems

land use restrict development in high flood risk areas, protect preserve open spaces

Municipalities can conduct education and outreach activities focused on flood awareness. All community members must understand their flood risk and be aware of the actions that they can undertake to mitigate potential flood impacts.

Communities that participate and are in good standing with the National Flood Insurance Program (NFIP) can volunteer to participate in the NFIP’s Community Rating System (CRS).

Flood warning systems avoid flooded areas and have time to protect evacuate

Conclusion

In conclusion, effectively mitigating flood risks is essential for protecting both residential and commercial sectors from the increasing threats posed by climate change. Understanding the distinct needs and priorities of these sectors allows for the implementation of tailored strategies that balance safety, economic growth, and community well-being. By combining structural and non-structural measures—such as building elevation, dry floodproofing, wet floodproofing, and green infrastructure—communities can enhance resilience to flooding. Additionally, strategies like improving drainage systems, investing in flood insurance, and developing business continuity plans play a critical role in ensuring operational stability for businesses. A comprehensive approach that integrates various mitigation options will not only safeguard property and infrastructure but also contribute to the overall sustainability and health of communities facing flood risks.

Definitions

• Flood Mitigation: Strategies and measures implemented to reduce or prevent damage caused by flooding.
• Structural Measures: Physical interventions, such as building elevation and flood barriers, designed to protect against flooding.
• Non-Structural Measures: Policies and strategies that do not involve physical construction, such as flood insurance and land-use planning.
• Wet Floodproofing: A technique that allows controlled entry of floodwaters into a structure to equalize pressure and minimize damage.
• Dry Floodproofing: A method of sealing a building to prevent floodwaters from entering.
• Green Infrastructure: Natural systems or engineered features that mimic natural processes to manage stormwater water and enhance resilience against flooding.
• National Flood Insurance Program (NFIP)
• Community Rating System (CRS): The Community Rating System is a voluntary program in which NFIP communities agree to implement specific flood risk reduction policies and programs that go beyond what is required under the NFIP.

Review Questions

1. What are some common flood mitigation strategies for residential areas?
2. How do the needs of residential and non-residential sectors differ when it comes to flood mitigation?
3. Describe the concept of wet floodproofing and when it might be an appropriate strategy.
4. What challenges might arise when implementing green infrastructure in urban areas?
5. Why is elevating critical infrastructure important in non-residential flood mitigation strategies?

Bibliography and Links

https://www.nationalfloodinsurance.org/flood-mitigation-techniques/

Building Science Resource Library | FEMA.gov

PROTECT YOUR PROPERTY FROM FLOODING

FEMA P-312

| Homepage | FloodSmart

| Flood Insurance Mitigation Discount Tool

http://wwwsp.dotd.la.gov/Inside_LaDOTD/Divisions/Engineering/Public_Works/NFIP/Pages/default.aspx

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