There’s a Reason They’re Called Floodplains

Since the start of mankind, rivers have played a vital piece in fostering colonies and settlements. The Mississippi is no different. The 3,800 kilometer long river and its floodplains host many farms and population centers. To help protect this infrastructure, river controlling devices such as levees, dams, and walls line the exterior of the river to help prevent flooding events. However, new studies show that these barriers might be causing higher frequencies and magnitudes of massive flooding events.

Research done across a number of different colleges, including Northeastern University, found that residents within the Mississippi floodplains could be in major trouble. By using a number of different methods including studying past stream flow data, past sedimentary samples, historical climate data, and current tree-ring lines, the researchers found that the river’s massive flooding events (100 year events) have increased by over 20%  and have seen an amplification of flood magnitudes over the last 500 years. They also found that 75% of this increase is due to human modifications of the river and its basin. The other 25% was found to be climate related.

Flodding
Aerial view of flooding of the Mississippi in Arkansas 2011 (photo by Lance Cheung)

The confinement of the rivers channel which occurs in part to the levees, is good at alleviating small flood risks but hugely magnifies ones that are able to over top them. Anthropogenic modifications to the river’s channel which began to appear in the early 20th century was seen to have a direct correlation with these more powerful flooding events. The rivers manipulated channel allows for little room to expand during flooding events, in order to protect the many farmlands and cities which line the exterior of it. This less natural flow channel means that when floods actually do surpass the protections in place to stop them, they do far more damage then they would have had the walls not been there in the first place.

Further problems arise when economic costs come into play. Because the rivers banks are so highly populated its almost impossible to relocate infrastructure already in place which would allow the river to take a more natural course. The lower half of the Mississippi river in particular is most in danger to flooding and thus has higher economic problems which occur when events top the levees. The researchers who conducted the study also predict the magnitude and frequency of mass flooding events of the Mississippi river are only going to continue to grow. This leaves the government in a tricky spot, should we start funding huge, extremely difficult and costly relocation projects or further risk devastating flood hazards by continuing artificial channelization.

For more information visit https://www.nature.com/articles/d41586-018-04061-z.

Source

Munoz, S.E., et al., 2018. Climate control of Mississippi River flood hazard amplified by river engineering. Nature. 556, 95-98.

2 Replies to “There’s a Reason They’re Called Floodplains”

  1. Interesting article! MI, LA, and FL are going to have to address this. Did you also look at how this would effect the Federal Flood Plain Insurance?

  2. Wow. It’s crazy how much we can impact our environment. I wonder if they got rid of the modifications, if it would allow the river to flow naturally and reduce the flood risk.

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