Click here or on the illustration above to see how the lock and dam system has converted the Mississippi's descent into a staircase of pools (250k graphic-expect slow download).

Until very recently, by nature's clock, water from the Mississippi River and its tributaries made its epic journey to the sea according to its own will. Water levels went up and down according to seasonal changes in precipitation and climate. Floods followed droughts which were preceded by more flooding.

But as the river became increasingly important for transportation and commerce, and as floodplains were developed for farming and building cities in the early to mid 1800s, public desire grew to control the river's unpredictable behavior. Mark Twain desribes in Life on the Mississippi the challenges presented by the untamed river for a river boat pilot in1874.

"Ship channels are bouyed and lighted...clear-water rivers, with gravel bottoms, change their channels very gradually, and therefore one needs to learn them but once; but piloting becomes another matter [on] the Mississippi and the Missouri, whose alluvial banks cave and change constantly, whose snags are always hunting up new quarters, whose sand-bars are never at rest, whose channels are forever dodging and shirking..."

Controlling the river for navigation meant removing dangerous obstacles like snags (see picture, above right*); establishing consistently deep channels; and regulating the river's flow to avoid extremely low water. Over a period of 100 years, a series of strategies changed the river to meet these goals. Many of these changes in the river, accompanied by changes in land-use practices, have increased the extent and impacts of flooding. This page reviews the kinds of changes that were made. Subsequent pages in this part of the web site will provide information on how these changes have impacted flooding.

*Illustration by Henry Lewis, courtesy of Univesity of Minnesota.

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