Humans are known for their impact on river ecosystems, wherein changes are made to the direction and movement of rivers to benefit human lifestyles. Some of these changes, however beneficial as they may be to navigability, can increase the severity of floods significantly.

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BBC describes some specific examples of how human impact on rivers has changed their flood patterns, such as dredging, or the practice of removing the silt at the bottom of rivers to deepen them. The idea is to prevent flooding by making the water flow faster, but in practice, the river can still be overwhelmed and faster and more dangerous floods can occur. Similarly, river straightening impacts the meandering movement of rivers that allow for slower water movement. The twists and turns of rivers prevent floods from moving at full speed.  

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A huge example of this is the Mississippi River, which has had levees built on it since the early 1800s. According to an article by ScienceNews, researchers have found that the efforts to reduce flood damage to people along the banks of the Mississippi have “increased the magnitude of the largest floods by 20 percent.” As described by Wired, these results were found in part by Samuel Muñoz, a geoscientist from Northeastern University. Muñoz and his team pulled mud cores from oxbow lakes in the Mississippi, to examine the layers and examine the river’s flood history. They compared their work to tree rings, which vary in size and change distribution in times of flood. Muñoz and his team then compared their findings to climate data and found that “Overall flood risk has gone up 20 percent,” but “75 percent of that risk comes from human engineering of the Mississippi for navigation and flood control.”

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Robert Criss, a geoscientist at Washington University in St. Louis, describes the impact even further by stating, “It’s like if you clog up your arteries with a bunch of cholesterol and get atherosclerosis, your blood pressure is going to go up. If you clog up the river with levees and navigation structures, you’re going to make floods worse.”

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Unfortunately, according to The Washington Post, Trump’s infrastructure plan is likely to only make things worse. The plan will make it harder to fund new flood protections, and the Mississippi River Cities and Towns Initiative, a group that works for river protection and management, worries that proposed budget cuts will “kill off other federal programs that already pay for river infrastructure, such as a Transportation Department grant program that has spent $162 million in recent years to help pay for new bridges, ports and riverfront improvements.”

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We aren’t doomed to only ever experience harsher and harsher floods, however. The Independent lists potential ways to reduce flood impacts, one of which being to restore rivers to their natural courses. Other solutions, however, include more flood barriers, as suggested by CEO of UK Flood Barriers, Frank Kelly, who stated that, “As the threat and frequency of flood risk increases, the use of passive flood defense has to be the only realistic long-term solution.” Other solutions are more habitat based, such as protecting wetlands and planting trees that act as sponges to soak up excess moisture. Solutions are numerous, but if we want to reduce flood intensity to the highest degree possible, humans must stop changing their natural direction and flow.