Studying the effects of land use on sediment loads, Little Missouri National Grasslands, North Dakota

Abstract

The Little Missouri National Grasslands in North Dakota were established in 1960 and are publicly owned lands administered by the U.S. Department of Agriculture (USDA) Forest Service. The grasslands are not solid blocks of National Forest Systems lands but are lands intermingled with other Federal, State, and privately-owned lands. The mixed-ownership pattern creates a unique environmental management arrangement within each grasslands area. The USDA Forest Service needs to determine how changes in land use affect loss of sediment from the grasslands, especially during periods of high runoff or after a grassland fire. Excessive sediment loss has the potential to destabilize hillslopes and channels by increasing runoff potential, by prohibiting natural revegetation, by changing animal habitation patterns, and by impacting areas farther downslope and downstream of affected areas. On October 31, 1999, two major grass-land fires occurred in the Little Missouri National Grasslands area. The Squaw Gap Fire affected 51,627 acres and the Rough Creek Fire affected 7,979 acres. Runoff caused substantial erosion when many road ditches and culverts were filled with sediment and some roads were washed out. In order to implement the best management practices within the Little Missouri National Grasslands, the USDA Forest Service will need sediment information related to land-use changes such as burned and unburned areas and grazed and ungrazed areas. The Little Missouri National Grasslands are located along the Little Missouri River in western North Dakota. The Grasslands are comprised of 1,028,000 acres predominantly in an area of rolling hills, sparsely covered buttes, coulees, woody draws, and badlands. Most of the area is used as rangeland; but, some of the area is cultivated or used for oil and gas development. The Grasslands have semiarid climate with short, warm summers and long, cold winters. The Grasslands receive an average annual precipitation of about 13 to 15 inches, which generally occurs from April through June. Runoff is produced by snowmelt during the spring or by rainfall over individual watersheds during the warmer months. Temperatures have ranged from about -30 degrees Fahrenheit during the winter to over 100 degrees Fahrenheit during the summer. The average growing season is about 125 days.