Submitted to: Trans American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: March 30, 1997
Publication Date: N/A
Technical Abstract: The Goodwin Creek Experimental Watershed covers 21.3 square kilometers in area and is located in the bluff hills region of the north central part of the state of Mississippi just east of the flood plain of the Mississippi River. Watershed topography ranges from small alluvial valleys along the major channels to moderately hilly uplands. The land surface ranges in elevation from about 71 to 128 m above mean sea level, with an average channel slope of 0.004. Stream flow is flashy following storm events and overbank flows are rare because of the large size of the incised channels. Flows with sufficient strengths to move a significant portion of the bed material occur on average 23 times per year, usually during intense convective storms in winter and spring. Median sizes of the bed material in the main stream range from 0.49 mm in the upper sections of the watershed to 6.92 mm in the larger channels downstream. Land use on the watershed has been surveyed annually and the percentage of cultivated land has decreased from 26% in 1982 to 12% in 1990. Since 1990 the percent of cultivated land has remained at about 12%. From 1982 to 1990, the concentration of fines (<0.062 mm) in Goodwin Creek have decreased by 62%, concentrations of sand (0.062 - 2.0 mm) have decreased by 66%, and concentrations of gravel (> 2.0 mm) have decreased by 39%. A decrease in the percentage of cultivated land affected the sediment budget of the watershed in two ways. A source of readily eroded sediment was removed, and the energy of the flowing water available to erode and transport sediment was reduced. The reduced flow in the channels from the decrease in cultivated land was probably the main cause for the lower transport rates of sand and gravel.