Alternating extremes of heavy rainfall and drought are making it harder for the Army Corps of Engineers — which must by law maintain the Mississippi River for commerce, including the transportation of grain — to predict and plan a multi-million-dollar practice of constant dredging. In the upper reaches of the navigable part of the river, a narrow landscape makes it difficult to find a place for dredged sand. Now, the continuous flow of sediment is straining old storage agreements.
