DETERMINING THE EFFECTS OF A BRIDGE SEDIMENT TRAP IN LAKE MAUMELLE, CENTRAL ARKANSAS

Lake Maumelle is a drinking water reservoir with an area of 8,900 acres, located fifteen miles northwest of Little Rock, Arkansas, USA. It meets 60% of the water demands for fifteen cities and communities, serves as a recreational site for boating and fishing and provides habitat for fish and wildlife. Managing the water quality of this reservoir is very important to maintaining the quality of life in central Arkansas. The reservoir is elongated in the E-W direction and has one major inflow at its western end that is constricted by a causeway and bridge. We hypothesize that this constriction forces sedimentation in the adjacent bay, thereby reducing the amount of sediment within the rest of the reservoir. We collected bottom sediment samples from east and west of the bridge to determine the grain size distribution. Data from six locations, three on the western side of the bridge and three on the eastern side of the bridge, were collected using an Ekman dredge. Sampling occurred along a traverse from the western portion of bridge, where runoff from Maumelle River is located, to the eastern portion of bridge. Preliminary results from grain size analysis indicate that the bridge acts as a sediment trap forcing deposition of much of the sediment load at the western-most end of the reservoir. Measuring the quantity of settled material, with a hydrometer, along the 6 locations can give insight to sedimentation interruption.