Many reservoirs in the country are aging and dredging has been the most common means to maintain continuing function of varied reservoirs. This study is to investigate geographic distribution of sediment deposits in a reservoir to gather information to develop the guidance for the future dredging program for other similar reservoirs. Charles Mill Lake, located near Mansfield, Ohio, was constructed on the Black Fork of the Mohican River in 1935 by the U.S. Army Corps of Engineers. The lake and surrounding areas are owned by the Muskingum Watershed Conservancy District and the dam is owned and operated by the Corps. The lake has a surface area of 1,350 acres with a maximum water depth of 34 feet at conservative pool level, i.e., 997 feet mean sea level. The watershed that supplies the lake is approximately 217 square miles. The reservoir was constructed for controlling floods, maintaining and enhancing the recreational opportunities, and improving the quality of life for residents and users of all the facilities within the watershed. It has been reported that significant sediment deposition has gradually reduced the effectiveness of the man-made reservoir over the years. The sediment deposits in the lake has affected flood control and the preservation of natural resources, including recreation, navigation, and water quality. Based on the recent topographical survey and the original topographical map of the lake, sixty sampling locations were selected to geographically represent the lake. A gravity corer, two feet long and three inches in diameter, was used to collect sediment samples. These samples were first classified by color by using a Munsell Soil Color Chart, developed in cooperation with the Natural Resources Conservation Service. The general physical make-up of sediment deposits was then recorded in a field book. Each sample of sediment deposit was then bagged and marked with its geographical location by a global positioning system and physical landmarks in conjunction with a detailed map of the area. Samples were dried and analyzed by mechanical sieve kit to classify percentages of grain sizes for all sampling locations. Grain sizes and colors of sediment deposits at sampling locations were assumed to be geographically referenced variables, which were by the kriging method to obtain a regional distribution. The analysis of kriging, a spatial interpolation technique, is based on the linear unbiased minimum variance estimation. The kriging analysis of sediment grain sizes and colors resulted in vector values for a grid of points covering the studied lake. These point values were converted into a grid of raster-based values to express the distribution by spatial images. These images were used to develop the guidance for the future dredging program.

1. Professor, Civil Engineering Department, Ohio University, Athens, OH 45701.

2. Graduate Student, Civil Engineering Department, Ohio University, Athens, OH 45701.

3. Manager of Projects, Muskingum Watershed Conservancy District, Ohio.

Water Resources Engineering Conference
August 1999

For more information on this or any other paper contact Terry Chang by email at tjchang@bobcat.ent.ohiou.edu