Response of the Minnesota River to Variant Sediment Loading

We perform an analysis of the response of a reach of the Minnesota River, US to changes in sediment loading, including sand and mud. The reach in question extends 160 km downchannel from Mankato to the confluence with the Mississippi River. To develop a morphodynamic model of this reach, we consider a one-dimensional formulation of coupled flow, sediment transport, and channel bed/floodplain morphodynamics and derive model inputs from field parameters where possible. We show that the output of wash load (mud) is about four times that of bed material (sand) and that changes in bed material input have little effect on sediment output over 600 years. That is, sand input is mostly sequestered in the study reach. However, changes in wash load input have a near-immediate effect on sediment output. Thus, reducing the input of wash load would have a greater impact on sediment delivery to the Mississippi River than reducing the input of bed material load. (c) 2020 American Society of Civil Engineers.