When the levees break, we’ll have a more sustainable landscape again
Thursday, December 10th, 2009
We don’t ordinarily think about climate change and land use change as being a synergistic threat to society. However, the combination of impervious surfaces that increase runoff, declining wetlands, levees, and more severe storms pack a quadruple whammy that could lead to some major flooding in the future. From the cool adaptation work done in Keene, NH, we know that much of our infrastructure (roads, bridges, culverts) can’t handle the added stress of streams and rivers with higher discharge. We’re looking at a potential nightmare of increased costs associated with infrastructure damage.
In this week’s issue of Science, Jeffrey Opperman and colleagues argue1 that our historical paradigm of flood control with levees needs to fundamentally change to achieve a more sustainable socioecological system.
Their solution? Tear down some of the levees to allow some floodplains to flood. This can accomplish several goals:
(1) Flood risk reduction
- Move to flood-tolerant activities in floodplains so that we don’t have to spend so much on disaster relief.
- Storing water in floodplains takes the strain off downstream regions because floodwaters can naturally spill to where they are supposed to rather than swelling channelized rivers. Small amounts of land can accomplish this—they cite a study of the Illinois River showing that a floodplain of 8,000 hectares would drop the likelihood of flooding 26,000 hectares of cropland by 50%.
(2) Increased floodplain goods and services
- Several economic activities are conducive to periodic flooding: pasture, timber, and flood-tolerant biofuel crops, such as willow.
- Periodically flooded soils can also assist with reducing erosion and storing nutrients that would otherwise reach and pollute coastal oceans.
(3) Building resiliency to climate change
- They argue that reconnecting rivers to floodplains can help us adapt to climate change in ways that are socioeconomically beneficial. For instance, we presently have to keep some reservoirs partially empty to accommodate periodic flood waters. But partially filled reservoirs can’t generate as much hydropower or provide as much drinking water. If we used floodplains as a natural pressure relief valve, we can operate reservoirs closer to capacity and benefit economically.
Opperman and colleagues acknowledge that there are political hurdles, such as convincing some private landowners that flooding their land can be useful.
But there are creative solutions that have already been deployed. They cite Sacramento as an example: Some farmers allow their crops to flood, serving as a pressure-relief valve when rivers swell, thereby preventing more expensive damage. In return, the farmers are compensated for their crop loss. It’s a win-win situation that presumably costs less than dealing with infrastructure damage or having to build new infrastructure that handles greater flooding.
Another idea is to allow some of these areas to become wetlands and compensate people as part of a wetlands banking system to mitigate the loss of wetlands elsewhere. This would most likely have several ecological benefits, including increasing habitat for wetland-dependent species such as waterfowl and other migrating birds. It would also likely increase vegetation productivity and carbon storage.
It’s interesting to note that they don’t call for an end to economic activity or human use in floodplains. Sure, we probably want to stop building McMansions in flood-prone regions. However, there are several ways we can use floodplains for ecological and economic benefit. These will likely require compensation, but in the long run, it’s cheaper than having to re-tool major infrastructure to handle greater discharge with climate warming.
1Opperman, J.J. et al (2009) Sustainable floodplains through large-scale reconnections to rivers. Science 326:1487-1488.
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Photo credit: http://www.flickr.com/photos/doblonaut/ / CC BY-NC-SA 2.0
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