River Flooding: Man-made or Natural Disaster?

The wild weather and disasters that have struck the U.S. this spring have been awesome and disturbing. Many have lost lives,homes, and livelihoods. The flooding along the Missouri and Mississippi Rivers has been at historic levels. People have always feared flooding and for good reason. Floods account for a large toll of lives lost every year. Are the floods we are experiencing man-made or natural disasters?

I think a case can be made that much of the flooding is a man-made event. Obviously, humans don't control the rain and snow melt (I won't consider the effects of humans on climate change at this time). However, humans have made grand designs and structures to control the rivers.* We have channelized the rivers with levees and controlled the flow with dams. This has resulted in people settling and building near the rivers and in areas that would be threatened regularly by flood if not for the built features. Humans also influence the amount of land area available to absorb the runoff from rains and snow melt. Reductions in undisturbed land, vast areas of pavement, and features that channel storm water all affect the amount and rate that water joins streams. The flooding waters carry bacteria, viruses, and parasites as well as an array of chemicals into the affected areas (Black 2008).

The strategies that we use to control flooding are changing. Communities and government officials are realizing that old "nature taming" approaches have been flawed and can make the results of floods even worse while not allowing the natural role of flood waters to be realized. We humans need to be more intelligent in designing our built environment to work with nature, knowing that nature's powerful forces cannot always be overcome. Listen to a discussion among experts about the Mississippi River and flooding broadcast on May 13 on National Public Radio here.

Environmental health professionals often play an important role in preparing for and responding to floods and other natural disasters. It seems time for EH to also become involved in influencing the design of communities and built environment features that influence the frequency and severity of the flooding.

*Everyone knows about the Continental Divide? All of the water that falls on the east side runs to the Atlantic and all that falls on the west side runs to the Pacific, right? This is not correct, due to man made intervention. In 1890, engineers in Colorado's high country built the "Grand Ditch" to capture water on the western slope and carry it to the eastern slope and thus supply thirsty Front Range communities! Water that has fallen on the western slope crosses the divide and flows east in the Ditch!

References
Black H 2008. Unnatural Disaster: Human Factors in the Mississippi Floods. Environ Health Perspect 116:A390-A393. doi:10.1289/ehp.116-a390. Accessed June 6, 2011.
"Struggling To Contain A Rising Mississippi." National Public Radio. May 13, 2011.