Realizing the benefits of largescale property acquisitions to reduce flood risk

When neighborhoods in the United States flood repeatedly, cities often look to purchase homes that bear the brunt of the damage and become unsafe places to live. Cities can access Federal Emergency Management Agency (FEMA) funding to purchase these flood-prone homes should the property meet benefit-cost and hazard mitigation criteria and the owners agree that it’s best to sell and move.

But sometimes, when individual homes are acquired and demolished, the empty lots that remain in their place can leave neighborhoods looking like a checkerboard.

“Vacant lots have a negative impact on the fabric of a neighborhood,” says senior planner John Bucher (Louisville, Kentucky). “They bring property values down. You end up with vacant properties that may not get mowed or that become a dumping ground. They can really have a depressing effect overall.”

Furthermore, it can be difficult to do anything meaningful with the resulting green space as acquired lots aren’t always side-by-side.

Multiple vs. Individual Acquisitions

But what if a city could purchase all the adjacent homes in a frequently flooded neighborhood, not just the ones that meet a specific benefit-cost ratio?  This is exactly what John and water resources engineer-in-training Jarred White (Cincinnati, OH) investigated.

Inspired by a real-life project in Wayne, NJ, they researched whether it was more cost-effective for communities to pursue multiple acquisitions on contiguous, flood-prone land—a “largescale acquisition”—rather than targeting only the best candidates for individual acquisition. They found that largescale acquisitions that are properly restored and maintained have more overall long-term benefits to offer than individual acquisition projects. However, there are no hard-and-fast rules for determining whether a largescale acquisition is always appropriate for a community.

Mitigation is very complex, according to the team, and although the long-term benefits may be higher overall, the short-term cost-effectiveness doesn’t always play out in favor of largescale acquisitions.

However, acquiring multiple properties can help houses that may not have met a mandatory benefit-cost ratio on their own to rise to the ratio necessary for acquisition funding. For example, House A’s ratio is 1.3, which meets the funding requirement of 1.0. House B’s ratio is only 0.9, not high enough. But combined into the same project, their ratio might level out at 1.1. As long as all of the homeowners voluntarily agree to participate in the program, then all of the structures can be acquired and demolished. This leaves not a checkerboard, but an uninterrupted swath of green space that can be restored to benefit the community.

The main idea behind largescale acquisitions is to reduce flood risk for as many people as possible while also expanding meaningful green space. This space can bring so many of the ecosystem services that benefit our everyday lives. Measurable benefits like improved air quality and reduced runoff, as well as less quantifiable benefits such as stress reduction and the building of social capital from having a communal space to gather.

Ecosystems as Service Providers

We don’t often think of ecosystems as “service providers,” but they are. In addition to giving us clean air, water, and food, ecosystems provide more specialized services like flood mitigation, landslide prevention, and pollution containment. The value of these services should be accounted for in any benefit-cost analysis.

As part of their study, the team also wanted to understand how the cost-effectiveness of a largescale acquisition changes when you use different values for ecosystem services. For instance, if one benefit-cost analysis uses a value of $X of benefit per acre for wetlands, but another benefit-cost analysis uses a value of $Y of benefit per acre for wetlands, then how does that difference in value for the same ecosystem service (wetlands) change the final benefit-cost ratio result? Additionally, which is the more appropriate value to use?

Not surprisingly, the team found that cost-effectiveness depends heavily on the dollar value being used, so having the most accurate ecosystem service value possible is key to the equation. Preferably, this would be a value that is specific to the geographic area where you are performing the assessment.

Final recommendations

The team accessed funding for their study and final report through Greenlight, part of Stantec’s Creativity & Innovation Program, which supports our people’s good ideas. “Support from Greenlight helped us take our time with the project and transform a standard report into something we think will capture the attention of the stakeholders and community officials we are trying to help,” says Jarred, the project’s technical lead. “I hope this project helps empower communities to go after larger, more impactful flood mitigation projects.”

Their research resulted in several recommendations for assessing the feasibility of largescale acquisitions, including:

• Largescale acquisitions are a good option with long-term cost effectiveness if approached carefully and on their own merits
• The way that land is managed post-acquisition must be thoughtfully planned to maximize benefits
• The dollar value of ecosystem services used in benefit-cost analyses impacts cost-effectiveness; therefore, developing regional (as opposed to national) ecosystem service values is encouraged

The message to communities is simple, says John: You can make these projects work.

“It may not be as simple and your benefit-cost ratio may not be as high, but your benefits will be greater and in the end you will end up with something that’s better for your community than the checkerboard approach,” says John, the project’s planning lead. “Don’t be afraid to try and put a largescale acquisition together.”

"Ultimately, the decision to pursue individual versus largescale acquisitions depends on variables like how the land is being restored, the ecosystem service values you use, flood hazard conditions, and much more. It all makes a difference."

“We hope our work helps shed some light into what’s possible with largescale acquisitions, and by doing so we can do a little bit more to help protect our communities from flooding disasters.”

And that could be a game changer for the places we call home.

About this article

This article is part of an ongoing series focusing on the value Stantec’s Greenlight program brings to clients, communities, and employees. Through Greenlight, Stantec invests up to $2 million annually to fund employee ideas that benefit our clients, community, and Company. Greenlight is part of our Creativity & Innovation Program, which celebrates and encourages creativity and innovation at work and in our work. Check back soon for another story in our Greenlight series.