PERSISTING SEDIMENT YIELDS AND SEDIMENT DELIVERY CHANGES

The Buffalo River is a tributary to the Mississippi River in west-cent ral Wisconsin that drains a watershed dominated by agricultural land u ses. Since 1935, backwater from Lock and Dam 4 on the Mississippi Rive r has inundated the mouth of the Buffalo's valley. Resurveys of a tran sect first surveyed across the lake in 1935 and cesium-137 dating of b ackwater sediments reveal that sedimentation rates at the Buffalo's mo uth have remained unchanged since the mid-1940s. Study results indicat e that sediment yields from the watershed have persisted at relatively high levels over a period of several decades despite pronounced trend s toward less cultivated land and major efforts to control soil erosio n from agricultural land. The maintenance of sediment yields is probab ly due to increased channel conveyance capacities resulting from incis ion along some tributary streams since the early 1950s. Post-1950 inci sion extended the network of historical incised tributary channels, en hancing the efficient delivery of sediment from upland sources to down stream sites.