Reviewed by Alex SmithApr 5 2022
As a result of a new grant awarded by the National Science Foundation, a Rice University-headed group of climate scientists and engineers is gaining better insights into how climate change could affect the frequency and intensity of flooding on the Mississippi River.
Sylvia Dee. Image Credit: Rice University.
“The real question motivating our research is: How will climate change alter the frequency and magnitude of flooding on the river?” stated Rice’s Sylvia Dee.
Over a quarter of the US population lives within the Mississippi River watershed, a region that is bigger than 1.2 million square miles including the drainage basins of tributaries like the Ohio, Missouri, Tennessee and Arkansas rivers.
Both intense rain and drought will be encouraged by climate warming, since warmer air that is dry will parch soil more rapidly, thereby resulting in an increase in evaporation.
However, warmer air can also hold more moisture, resulting in more extreme rainfall. Dee remarked that uncertainty remains around which of these effects will be dominant and when. Also, there is a need for flood risk managers to know the information so that they can plan correctly for the next century.
It’s actually quite complicated because the basin is so large and there are multiple tributaries. You’ve got the Missouri in the west and the Ohio in the east, and they are generally experiencing very different weather patterns.
Sylvia Dee, Assistant Professor of Earth, Environmental and Planetary Science, Wiess School of Natural Sciences, Rice University
Dee added, “It might be very dry over the Missouri and very wet over the Ohio. So to figure out if the Mississippi is going to flood more or less often, we have to understand the hydroclimate over all of the tributaries individually.”
Dee stated that the scientists will “look at the heterogeneity of the different tributaries” and gauge how every system will act and add up to water flow under possible climate futures.
Doss-Gollin, an assistant professor of civil and environmental engineering in Rice’s George R. Brown School of Engineering, said, “Some modeling studies have suggested that the drying effect dominates and others show that the precipitation effect dominates. To constrain this uncertainty, we need to look at data from the distant past.”
A comparison will be made by the researchers with its models along with paleoclimate data obtained from tree rings, sediments and other records of wet and dry periods earlier.
The fundamental question is: Which effect will win, the increased evaporation and drying or the increase in extreme precipitation?. And the follow-up is: 'How will both of those changes, probably working together, affect the statistics of floods?
Sylvia Dee, Assistant Professor of Earth, Environmental and Planetary Science, Wiess School of Natural Sciences, Rice University
For instance, Missouri spans few of the northern Rockies.
Dee stated, “There’s a lot of data suggesting the snowpack is going to be greatly reduced in a warmer climate. Snow melt in the spring contributes a lot of water to the lower part of the Mississippi delta. So a reduced snowpack could really reduce discharge.”
Dee added, “But on the other side, we expect rainier conditions over much of the Northeast, including the Ohio River basin. If the Ohio gets wetter and the Missouri gets drier, what does that mean for flood control?”
The levees, dikes, locks and other infrastructure that regulates floods and keeps trade moving on the Mississippi are considered a marvel of modern engineering. Dee stated that one of the major goals of the research group is sharing what it learns with the US Army Corps of Engineers, the agency that builds, designs and controls that infrastructure.
We can run models until we’re blue in the face, but what flood risk managers need to know is if those models are making projections that are accurate. We talked extensively with collaborators at the Corps for this proposal.
Sylvia Dee, Assistant Professor of Earth, Environmental and Planetary Science, Wiess School of Natural Sciences, Rice University
Dee added, “We drew from their reports about climate change and flood risk, and we talked to them about what they needed. We want to make sure the science we’re doing is relevant to them.”
Muñoz is working as an assistant professor of both marine and environmental sciences and civil and environmental engineering at Northeastern.
The land drained by the Mississippi River and all its tributaries
The land drained by the Mississippi River and all its tributaries. Video Credit: Rice University.