Monitoring Of Gully Erosion Development: Process And Dynamics

Application of high technology to study dynamic process of gully erosion development has important theoretical value for the understanding of soil erosion process and mechanisms. Based on successively simulated rainfall being carried out at hillslope-gullyslope system (3 m×13m), hillslope gully erosion development was simulated; three technologies of high precision GPS, 3-D laser scanner and needle board methods were used to monitor erosion morphology change process and feasibilities of monitoring gully eroiosn development by using three technologies were analyzed; on base of measurement of soil loss, estimated precision of soil loss by three technologies were evaluated and advantage and disadvantage for three measurement technologies were discussed. The research results provide methods and technologies for monitoring soil erosion process. The main results were as follws:1. Gully erosion development process was simulated. The development processes from sheet erosion to rill erosion and then to gully erosion were reoccurred. The development process characteristics of sheet erosion developing to rill erosion and then to gully erosion were described in detail.2. On base of charactics of different measurement methods, data processing for each measurement technology was presented. High precision GPS required the establishment of four reference points before surveying which were also used to delineate the surveyed surface (surface-area). 3-D laser scanner needed standard targets and high-reflective material stickers around the surface. Needle board demanded calculating slope length-steepness relationship.3. Simulation degree of eroiosn morphology by three measurement methods was analyzed. Combined erosion morphology development by successively simulated rainfall with Arcgis9.0 spatial analysis, erosion morphology of different stages for gully erosion development was simulated by grid processing of measured data of three measurement methods. 3-D laser scanner gave the best description for sheet erosion. The insides of deep channels were not measured due to deep gully. The images generated by high precision GPS were better to simulate erosion morphology; the generated images were corresponding to the digital photots in detailed. Simulated degree of erosion morphology by needle board methods was weak.4. Three measurement methods were used to dynamically monitor gully erosion development process. Gully erosion development processes by the simulated images generated from the high precision GPS, 3-D laser scanner and needle broad method were analyzed. The results showed that the images generated by 3-D laser scanner could re-produce traces formed by sheet erosion and mini-rills; they could better reflect erosion development process from sheet erosion to rill and rhen to gully. The images generated by high precision GPS could perfectly reflect spatial distribution of erosion patterns and developing process from rill erosion to gully erosion and rill numbers and their shaps; they could not describe traces formed by sheet erosion. The images produced by needle broad method could use to describe spatial distribution of erosion intensity and dynamic development process from rill to gully, but they were weak to describe dynamic development process from sheet erosion to rill erosion. When rill width was larger than memeasuring needle density, these rills could be well descripted by needle broad method.5. The estimated accuracies of soil loss by three measurement methods were compared. Through grid insert processing method based on the points data of three measurements, erosion volume was calculated by using 3D analysis function. The results showed that the estimated accuracy by 3-D laser scanner was best; and the errors of estimated soil loss by 3-D laser scanner, high precision GPS, and needle broad method were 4.56%, 7.38%, and -17.19%, respectively.6. The measured data could be pre-proceesed with noise reduction and erroneous-point removal before using measured data by three measurement methods to generatie images. The AutoCAD software aided to process data in order to use the measured data effectively. Methods and steps for pre-processing these measured data were described in detail.