During the construction of the Missouri River navigation channel, the Army erected thousands of pile dikes and revetments to narrow, deepen, and straighten the wide, shallow, meandering stream. Once the engineering works went into the river, the Missouri deposited its heavy silt-load on the downstream side of the structures. Overtime, new, elevated lands appeared in the river’s floodplain. Side channels, marshlands, and scour holes – everything that constituted the floodplain – filled with alluvium. Accumulated sediments sharply reduced the floodplain’s ability to store floodwater. Valley farmers benefitted from the newly accreted land. They expanded their operations into the floodplain, planting row crops where native vegetation once grew. The floodplain’s loss meant the farmer’s monetary gain.
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U.S. Geological Survey hydrologists recently reported that the Missouri’s present flood is carrying far less sediment than previous floods. The reason is simple; the high flows are coming out of the Dakota reservoirs rather than from the Lower Missouri’s dirtier, uncontrolled tributaries. The upstream reservoirs are trapping the river’s silt load and discharging clearer water through spillways and outlet tunnels. 
