Suspended sediment in Trail Creek at Michigan City, Indiana

Trail Creek is a small (54.1-square-mile drainage area) tributary of Lake Michigan located in northwestern Indiana. A harbor at the mouth of the stream has experienced excessive sediment deposition. A study was done to investigate the suspended-sediment characteristics of Trail Creek. The study included analysis of suspended-sediment concentration and particle-size data, and estimates of annual suspended-sediment load. Suspended-sediment concentrations ranged from only a few milligrams per liter at low flows to about 300 milligrams per liter at high flows. At low flows, the suspended sediment was mostly silt- and clay-sized material (less than 0.062 millimeter). The percentage of silt- and clay-sized material gradually decreased to about 50 percent of the suspended sediment at high flows. Estimates of the annual suspended-sediment load for the 1981-90 water years were calculated by the flow-duration, rating-curve method. Annual loads ranged from 3,690 to 8,250 tons. The average annual load for the 10-year period was 6,180 tons. Annual suspended-sediment yield (load per unit drainage area) averaged 114 tons per square mile; this value is within the range of values from 14 other previously investigated streams in northern Indiana. Average annual yields of these 14 streams ranged from 11 to 152 tons per square mile; the median annual yield was 56 tons per square mile.