INTENSIVE SITE PREPARATION AND SEDIMENT LOSSES ON STEEP WATERSHEDS IN THE GULF COASTAL-PLAIN

The hydrologic effects of 3 methods of intensive site perparation - brush chopping, shearing and windrowing, and bedding on contour - were measured during 1976 and 1977 on 3 small watersheds on steep terrain in northern Mississippi. First-year sediment losses for the chopped, sheared, bedded and control watersheds were 12.5, 12.8, 14.2 and 0.6 metric tons/ha, respectively. Sediment concentrations for the 4 watersheds were 2471, 2837, 2808 and 2127mg/l of stormflow. Stream channel scouring was a major source of sedimenton the site prepared watersheds. Second-year sediment yields from the chopped, sheared, and bedded watersheds decreased to 2.3, 2.2 and 5.5 metric tons/ha, while sediment from the control watershed decreased to 0.1 tons/ha. Sediment concentrations were 670, 794, 2346 and 393 mg/l for the 4 watersheds.-from Author