Part I Physical Modeling Of The Chippewa River - Mississippi River Confluence

A physical model of the confluence of the Chippewa and Mississippi Rivers, 1 to 200 horizontal and I to 40 vertical scale ratios, was constructed and tested. Commercially available sand, having the mean diameter of 0.42 rom, was used as the bed material. with this bed material it was found necessary to distort the Froude number by a factor of 1.85 in order to simulate the sediment movement correctly. The model was successfully calibrated by reproducing the bed profile change which occurred in the field between the fall of 1977 and the spring of 1978. The model was tested for eight different conditions. Four runs were specifically devoted to measuring the velocity distribution, water surface profile, and the bed profile under steady flow conditions. Two r,uns were conducted to study the filling process of a dredge cut in the Mississippi River. A run was made to study the response of the river to an extreme condition~ a combination of a very wet year in the Chippewa River and a very dry year in the Mississippi River. The last run was for the study of the effect of a low head dam in the Chippewa River. This report describes the results of, these experimental runs and presents conclusions and recommendations.