Uncovering JAPA

Mitigating Flood Risk Through Smart Land Use Practice

Floodplain management, as a function of land-use policy, plays a crucial role in mitigating the growing flood risks through regulation, especially as natural disasters occur with increased frequency as a product of climate change. While there is a growing body of research on hazard mitigation plans and policies, there is a noticeable dearth of data regarding floodplain development. Consequently, there has historically been very little information about how floodplain development patterns differ from one community to another and how policies, plans, and regulations influence outcomes.

In "Growing Safely or Building Risk?", (Journal of the American Planning Association, Vol. 90, No. 1), Miyuki Hino, Todd K. BenDor, Jordan Branham, Nikhil Kaza, Antonia Sebastian, and Shane Sweeney, present substantial evidence regarding the relationship between floodplain development, geographic and socioeconomic characteristics, and local flood risk management practices.

The article examines various strategies currently employed to address floodplain development, finding patterns that indicate deficiencies and opportunities for improvement. This analysis aims to enhance the effectiveness of mitigation efforts and the avoidance of flood risk.

Assessing Floodplain Development, Risk Management

The study measured floodplain development by quantifying the amount of housing and infrastructure within the regulatory 100-year floodplain over the past two decades. Subsequently, the researchers evaluated these development outcomes against community characteristics and local flood risk management efforts.

Two key indicators were utilized to assess local flood risk management:

  • Property buyouts that involved removing housing from floodplains.
  • Participation in a federal program known as the Community Rating System (CRS).

The study focused on North Carolina, chosen as an excellent candidate due to its rapid population growth and susceptibility to recurrent flooding. The state's extensive data on flood risks, coupled with a substantial track record of property buyouts, provided valuable assets for conducting research.

Throughout the study period, North Carolina faced 29 significant disaster declarations, impacting both coastal and inland communities. By examining every community in the state, the research covered a broader geographical area, offering a more comprehensive and diverse representation of communities than previous analyses.

Study Reveals Challenges in Floodplain Development

The study discovered that over 75,000 acres of vacant floodplain land are zoned for development in North Carolina, spanning 85 municipalities and counties. Despite ongoing community efforts to mitigate flood risk through property buyouts and participation in CRS, there continues to be significant development in flood-prone areas.

Throughout the 22 years under examination, statewide property buyout initiatives equated to just two to three years of new construction within floodplains. During this timeframe, 5,234 properties were bought and restored to open space, while over 59,000 parcels in floodplains were developed for residential use.

Between 1996 and 2017, the study found that 10 new residences were constructed in floodplains for every property buyout, highlighting a clear indication that existing policies and incentives are not robust enough to address the increasing frequency of natural disasters due to climate change.

Several hurdles impeding the effectiveness of property buyouts include their dependence on homeowners' willingness to sell their flood-prone land to the government and the administrative capacity of the government to carry out property buyouts.

The Community Rating System (CRS) is a voluntary program administered as part of the National Flood Insurance Program (NFIP) that establishes prices and mandates flood insurance coverage for most floodplain properties. To benefit from discounted flood insurance premiums through the CRS, communities must adopt a floodplain management ordinance that meets minimum criteria.

One of the CRS's shortcomings is that some participating governments prioritize emergency flood management over long-term planning solutions to proactively mitigate risks. This leads to a reactive, rather than a proactive response.

Additionally, federal funding typically covers most post-disaster recovery costs from major events, making it easier for communities to stay and rebuild in flood-affected areas. In essence, there's little incentive to move out of high-risk areas; it could be encouraging further development in floodplains.

Figure 2. Construction of new housing in the floodplain far exceeded property buyouts in North Carolina over the last two decades.

Figure 2. Construction of new housing in the floodplain far exceeded property buyouts in North Carolina over the last two decades.

Tools to Shape Floodplain Development

Local governments have various tools to shape the location and character of new development. One approach is to incorporate stringent flood-proofing requirements into local ordinances, using rule-based zoning to make development in floodplains more challenging. Alternatively, leaders can incentivize development in less hazardous areas through tax incentives.

Another effective strategy is acquiring vacant floodplain land to prevent future development altogether. In many cases, the cost of such acquisitions is lower than the damages avoided from flooding, sometimes by more than two to one.

The empirical evidence gathered from a 20-year assessment of floodplain development serves as a valuable resource for decision-makers aiming to enhance flood mitigation plans and policies. Developing evidence-based policies that promote informed, climate-responsive development is crucial for effectively addressing community flood risk, especially as extreme weather events fluctuate in frequency and severity.

Top image: iStock / Getty Images Plus - RoschetzkyIstockPhoto

Lucas Flint is a master's student in urban planning at Harvard University.

January 11, 2024

By Lucas Flint