Preventing flooding through levee setbacks

A Q&A with Matthew Chambers

Matt Chambers is a PhD student working under IRIS Director Dr. Brian Bledsoe. His work modeling the impacts of levee setbacks on upstream and downstream communities highlights how natural infrastructure solutions can increase community resilience. 

In the past, engineers attempted to prevent rivers from flooding by placing tall walls on either side of them, called levees. However, these structures are known to catastrophically fail during extreme weather events, causing mass flooding in the towns and cities depending on them. The practice of “setting back” levees involves relocating levees back from a river’s banks to leave more room for the river to flood.

Join us for a Q&A with Matt Chambers to learn more about the important work IRIS is doing to rethink riverine flooding.

How does this research have the potential to change the world?

This research can help protect lives and the livelihoods of those that live and work in levee protected areas. A levee setback, or relocation of a levee back from a river, is a reasonable solution to flood risk mitigation on highly leveed rivers, though this may be contrary to what a person might think. It is because levees channelize rivers and increase water depth by restricting conveyance area. The addition of a new levee, to a highly leveed river, increases water depth by further channelizing the river. Levee district engineers may be prompted to raise the height of old levees in reaction. As development increases along a river, and new levees are installed, the engineers may repeatedly build all the levees taller. It’s a feedback loop of sorts. We can build taller, stronger, levees and act in reaction to levee breaching floods; or, we can get creative, and think of new ways to reduce stress on our most important levees, thereby reducing the likelihood of a breach and keeping those that live and work in levee protected areas safe.

Levee setbacks are one such creative approach N-EWN has targeted as having potential to solve this problem. A levee setback expands a river’s conveyance area, which allows flood waters to flow out onto floodplains at controlled locations. It lowers river depths up and downstream of the reconnected floodplain, thereby reducing stress on other levees in the network, and reducing the risk of breaching.

How are you conducting your research? What regions does it most closely apply to?

Our research is conducted with computer models of stream networks and floods. The program we use is called HEC-RAS and is an industry standard. In the future, we hope to test some of our ideas in real systems. Our target region is the Midwestern United States, for now, but we will ultimately expand to the broader Mississippi River Watershed. Some of our findings may be applicable more broadly, for example, to floodplain reconnection projects in the Northwest, Northern California, or even internationally. For instance, in Central Europe stream networks have been altered by channel controlling infrastructure for several hundred years and are thought to be at a heightened risk of increased flooding based on climate change projections.

Copyright © 2021 by the University of Georgia, contact Dr. Brian Bledsoe and Matt Chambers to request reprint.

What are your findings as far as the potential for NI to help reduce flooding? 

We are finding that NI has enormous potential to help reduce flooding in a variety of scenarios. And if designed with a holistic viewpoint of the stream network at watershed-level granularity, we may be able to design solutions that are protective against current flooding conditions and also resilient to projected future flooding conditions as our climate changes.

What are next steps for your research?

We have more potential avenues of research than hours to pursue them. One interesting avenue is exploring the problem of stream network desynchronization. That is, how do we strategically locate areas of reconnected floodplain in a broader stream network to alter the timing of flood waves, such that tributary flood waves do not amplify main stem flood waves down river? It’s a mouthful, but in essence, we are investigating changing the timing of floods in a stream network so that floods do not add together to create larger floods.

What do you find most exciting about your work? Most challenging? 

One of the most exciting aspects of our research, and a strong motivator for me, is the prospect that our work may be implemented in a real system. It is admirable to accurately model a system and make predictions about the benefits and shortcomings of a solution, but it is something else entirely to see your solution in action. Implementation in a real system is how we will know if our solutions work or not. And the process may be iterative. But the outcome could be an approach to flood risk mitigation that protects people’s lives and livelihood and undoes some of the environmental challenges we have created in our rivers with conventional engineering practices. The timeline for implementation is long, but I’m working toward that goal every day.

With a background in both engineering and ecology, your knowledge base is interdisciplinary. How do you feel that your knowledge in both fields currently informs your work? 

My background in ecology and engineering has helped me understand the perspectives of both practicing engineers and conservation biologists. I am hoping that as I get deeper into my academic career, this dual background will help me span the gap between disciplines in a field of research that is interdisciplinary by design and by necessity.  Our research is aimed at seeking natural infrastructure solutions for flood risk mitigation. When we reconnect a floodplain or remeander a stream to lessen flood severity, we design with natural features, such as topography, or bank vegetation, to satisfy engineering requirements. The “natural spaces” we introduce to engineered systems have the co-benefits of providing habit and restoration opportunities for conservation biologists.  

Do you have any collaborators or funding sources you’d like to acknowledge?

I would like to thank IRIS Director Dr. Brian Bledsoe, Dr. Rod Lammers, and our close collaborators at the US Army Corps of Engineers.