Dynimic Monitoring Of Gully Erosion Development By LIDAR

Gully erosion played an important role in soil erosion, and made significant contribution to watershed. Quantity study of gully erosion was crucial to understanding of soil erosion process. This papers constructed gully development models based on the the field topographical features of the early development of gully erosion. Dynamical monitoring of gully erosion development process on the loessial hilly-gully region was studied through artificial rainfall simulation and LIDAR technology. The main conclusions were as follows:(1) Dynamic monitoring of gully erosion processes using LIDAR technology was demonstrated. Compared the actual photos with the TIN MESH, the feasibility and accuracy of this technology was discussed. The comparison indicated that TIN MESH reflected the overall gully morphology well in various stages of the gully erosion. With the development of the gully, the characterization was better. The error between the measured soil loss and the estimated value ranged from 1.1% to 18.3%.(2) Effect of ainfall, slope and catchment area on gully erosion was studied. The result showed that rainfall intensity played more important role than topography on confluence time, depletion time, runoff rate, and sediment yield rate; catchment area was more important than slope in the topographic factors.(3) The dynamic process of gully erosion form was revealed. The gully head erosion was the main way with a serious head cut during the early stage of the gully erosion. The gully wall expansion and gully bed shear was active at active gully erosion development stage. In addition, gully wall collapsing was the main form of gully widening. The gully wall expansion rate was still relatively active but the rate significantly reduced, and the gully bed cutting rate reached stable at stable phase of gully erosion.(4) Spatial distribution of gully erosion under experimental conditions was analyzed. The maximum gully width was 0.5-1m under gully head, gully width was decreased with the slope length increase; the deepest of the gully was at 5-6m of slope length; gully depth inclined as the raised of the slope length at 5-8m; gully depth increased with the increased of slope length at 0-4m.(5)The contribution of gully erosion to total soil loss was quantified. Sediment yield of head cut accounted for gully erosion declined from 100% to 8.5% along with the rainfall; the proportion of the gully area compared with the total slope area expansed from 8.7% to 93.3% as rainfall processed; gully erosion accounted for an average proportion of 69.5% of the total soil loss.