Channel Changes in the St. Clair River Since 1933

The lowering of Lake Michigan-Huron levels because of the 25-ft and 27-ft improvement of the St. Clair River navigation channel was computed to be 0.20 ft for average flow conditions. Submerged sills in the upper reach of the river were selected as the method for compensation. Model tests conducted in 1934 indicated that a minimum of three sill locations are required in order to obtain the desired compensation. Tests of various shaped sills showed that sills with a vertical upstream face were the most effective, the downstream face having an insignificant effect. Variation of the slope of sill face from vertical to 1 on 3 reduced the effectiveness by 50% and, with the area between sills filled to crests, by 70%. It was shown that sand is transported from the lake into the river with evidence of deposits. Further model tests are planned to combat the problem of possible deposits in the sill area and also to test for the most effective placement of sills.