HYDROLOGY

Good Intensions Gone Awry

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Science  12 Oct 2001:
Vol. 294, Issue 5541, pp. 267
DOI: 10.1126/science.294.5541.267b

Large levees and channel structures, such as wing dams, were built on the lower Missouri and Mississippi rivers during the past century to help to mitigate damage from major floods. Recently, several devastating floods have hit the Mississippi watershed, and these events offer an opportunity to assess the impact of these flood control devices.

Criss and Shock compared floods in the Mississippi River, which contains many levees and in-channel dams, with floods on several of its major tributaries, which do not. Although the discharge during recent floods on the Mississippi River was equal to that of floods early in the last century before flood control devices were built, the flood stage or height on the Mississippi River increased by up to several meters because the engineered structures constrained the channel. The net effect of these changes is that the potential energy of any flood has increased and the recurrence interval between floods (based on stage height) has decreased.—BH

Geology10, 875 (2001).

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