Long‐term effects of navigation dams on a segment of the upper Mississippi River

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Abstract
Navigation dams on the upper Mississippi River have altered the long‐term relationship of river stage to river discharge. Analysis of the 34‐year pre‐dam and 74‐year post‐dam data sets indicated that the completion of Lock and Dam 19 in 1913 increased river width and volume behind the dam. The immediate impact was a higher mean river stage less influenced by changes in river discharge. The dam's long‐term impact was to increase sedimentation causing a steady loss of both river width and volume that resulted in stage/discharge relationships approaching those of the pre‐dam era. The present condition of higher mean river stage coupled with greater stage fluctuation is a major factor in the increased recurrence and duration of floods on the upper Mississippi River in recent decades.