Use of Ground-Based LiDAR to Assess Potential Sediment Loss from Stream Banks in Grazed Pastures.

Animal grazing on lands near streams has the potential to contribute sediment and nutrients to surface waters. To minimize the impact, we must understand of the effects of grazing systems on stream bank erosion. In this study, we used six 12-ha grass pastures that were each bisected by a 141-m stream segment.  Two replications of three management treatments [continuous stocking with unrestricted stream access (CSU), continuous stocking with restricted stream access (CSR), and rotational stocking (RS)] were randomly assigned to the six pastures. Pastures were stocked with 15 fall-calving Angus cows from May to October of 2006 and 2007.  To estimate stream bank erosion and deposition, we used ground-based LiDAR (Light Detection and Ranging) technology to capture a 3-D image of selected stream banks in each of the six pastures. Scanning was conducted (Leica HDS300 laser scanner, 6 mm accuracy at 50 m) pre- and post-grazing in both years. The scan data indicated that deposition was the dominant activity in each of the sites during the 2006 grazing season. During the 2007 grazing season, however, bank erosion occurred in four of seven sites. Net erosion or deposition did not differ among grazing management treatments in either year. In addition to LiDAR, we utilized traditional erosion pin measurements to estimate bank erosion and deposition within each of the grazing treatments. The data are now being used to compare LiDAR to erosion pin measurements for monitoring erosion and deposition of stream bank soils.