Flooding during June 2011 on the Missouri River floodplain near Arrow Rock, Mo.
A new study evaluates how increasing floodplain area affects ecosystem services along the lower reaches of the Missouri River. Credit: U.S. Geological Survey, Public Domain
Source: Water Resources Research

Floodplains provide many important ecosystem services. They are the front lines in mitigating the worst effects of flooding, offer aquatic and terrestrial wildlife habitats, help process nutrients transported by rivers, and provide floodwater storage. As a result, floodplains are among the most biodiverse habitats on the landscape. They are also used to maximize agriculture, industry, and transportation.

As extreme weather events increase, so too has flooding, often resulting in catastrophic damage. These floods have prompted river managers to consider how to increase floodplains’ resiliency while also reaping the socioeconomic benefits that rivers and floodplains provide.

In a new study, Jacobson et al. focus on the longest U.S. river—the Missouri—which is subject to heavy nutrient runoff from the region’s extensive agriculture. The researchers modeled a management approach that simulated floodplain inundation over several scenarios to understand how flooding conditions would affect wildlife habitat and nutrient processing.

The authors used an inundation model focused on the lower reaches of the river, the 500 miles (around 800 kilometers) from Rulo, Neb., to the confluence with the Mississippi River. They evaluated how submerging floodplains would affect waterfowl habitat and denitrification.

The results indicate that increasing floodplain inundation would significantly bolster waterfowl habitat, particularly in expansive floodplains. However, the model indicated that floodplain modifications have limited utility to mitigate nutrient inputs—a scenario without levees increased denitrification to only 3.6% of the current nitrogen load.

In addition, the authors evaluated how future climate change scenarios could affect floodplain connectivity, a key component in climate resiliency. Increasing connectivity turns out to be highly location dependent. The benefits from inundation are lower in areas with an incised channel and greater in areas where sediment buildup increases river-floodplain linkages.

The study highlights the challenges of managing and restoring rivers under changing climate scenarios and management imperatives. The authors note that management decisions for large-river floodplains will likely depend on specific locations. (Water Resources Research, https://doi.org/10.1029/2021WR031204, 2022)

—Aaron Sidder, Science Writer

Citation: Sidder, A. (2022), Missouri River floodplain expansion, services, and resiliency, Eos, 103, https://doi.org/10.1029/2022EO220367. Published on 28 July 2022.
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