Man-Made Levees: Do They Make Flooding Worse?

Photo by Justin Wilkens on Unsplash

Anyone living in towns or cities close to the Mississippi River know about the risks of flooding. During times of heavy rain, there is an increased possibility of river flooding. The common solution to prevent flooding is levees build around the river. However, are levees making flooding better or worse? According to scientists, they’re making floods worse.

Levees are not a new invention. Levees were used in ancient times by the Egyptians, Sumerians, and Mesopotamians to protect their farms and cities from floods. Fast forward thousands of years, the levee system has taken a turn for the worse.

In 1852, an engineer named Charles Ellet Jr. wrote a report warning the federal government building levees close to the Mississippi River will confine the water into a small channel; causing the water to rise and flow faster. In the report, Charles says:

“To the extension of the levees along the borders of the Mississippi, and of its tributaries and outlets, by means of which the water that was formerly allowed to spread over many thousand square miles of low lands, is becoming more and more confined to the immediate channel of the river, and is, therefore, compelled to rise higher and flow faster.”

The federal government didn’t heed his warning. Now over a century later, we are suffering the consequences of their bad decision.

Multiple analyses confirmed Charles’ position. The levees constructed along the river are increasing the risk of floods and putting people’s lives in danger. Nicholas Pinter, geologist and associate director of the Center for Watershed Sciences at the University of California Davis, says:

“What you’re doing in many cases is taking a flood plain out there — it can be 5 or 6 miles wide — and you’re forcing the water that would otherwise spread across that area to go through a narrow passageway.”

When the passageway gets narrow, the water will flow faster and rise higher. This increase in flow and height can cause the levee to break. With the levee close to the river, the water can’t return to the river after a flood. That is the reason why recovery after a flood takes a long time.

In a study published in Nature Research, a group of scientists attempted to study the effect of the infrastructure on flooding. The scientists examined the sediment and tree rings near the river dating back around 500 years. They discovered flooding has become more server and frequent over the past century and a half years.

It was around that 150-year mark when levee construction ramped up. Since the flood of 1927, the U.S. Army Corps of Engineers was required by Congress to begin building a massive system of levees on the Lower Mississippi.

Another problem with flooding is towns building higher levees than their neighbors. This forces the water to spill over areas where levees are smaller or areas with no levees at all. The side with the high levees stays dry, while the other side suffers millions of dollars in damages and lives lost.

One solution to reduce the severity of flooding will be for the towns by the river to have the levees the same height. This way, towns won’t have to suffer damages because one towns’ levees are higher than others. Another solution is to move the levees further away from the river. This allows the water to have more room to spread over the land when the river floods. Nature can have her floodplains returned and animals can return to their former habitat.