| The simulation and visualization of gully erosion development process is the hotspot and aporia in slope soil erosion research, which could discover soil erosion process mechanism and soil erosion law. Based on the continuous rain experiments and the model of hillyslope-gully system, this paper studied the spatial and temporal evolution of development process of slope-gully system surveyed the evolution process. of hillyslope-gully erosion form by the three-dimensional laser scanning machine, built the high resolution ratio DEM of hillyslope-gully erosion form, and the slope soil erosion simulated system based on GIS plug-in; studied the temporal and spatial process of hillyslope-gully erosion, and built the simulated models of gully development process and the visualization system of hillyslope-gully erosion. Main conclusions were as follows:1. The simulation of slope-gully erosion evolution process. This paper simulated the evolution process from sheet erosion,rill erosion ,then to gully erosion without transverse ploughing. there were four stages for the evolution process on loess slopes: 1) sheet erosion stage to rill erosion; 2) rill erosion development stage with increasing rill length and width; 3)the stage from rill erosion with relatively stable amount of soil erosion and a few sidewall collapse to gully erosion; 4) gully erosion stage with obviously increasing depth and width .2. Temporal and spatial process of hillyslope-gully erosion. This paper studied dynamic changing process of gully length, width, and depth, and distribution of slope gully erosion and the formation cause and. The results showed that the gully erosion speed was different at different time and different slope locations . At initial 50 min of rainfall, headward erosion was dominated in the gully development, when gully length reached steady, gully-wall collapse and gully channel deep-cutting were in lead position . compared with the Gully erosion development at the different locations, the soil erosion at III and IV slope sections were the most serious The highest width and depth were 1.31m and 0.59 m, respectively. At those two slope sections , gully erosion per unit gully length was 505-543 kg, and occupied 12%-13% of the total sediment delivery from the whole hillyslope-gully system. The sediment from 5-8m slope length took up 40.1% of the total soil erosion and sediment from 4-9m slope length took up 60.5% of the total sediment yield.3. The slope soil erosion simulated system based on GIS plug-in. This paper researched the application of plug-in technology to GIS system and built a computer simulation system for hillyslope-gully soil erosion by C# computer program under C#.NET and ArcGIS Engine SDK, based Plug-in technology and GIS. According to the soil loss data from 6-times simulated rainfall experiments and 6-times surface terrain data measured by three-dimensional Laser Scanner (LiDAR), it simulated the erosive form of slope-gully system and estimated the amount of soil erosion; further more the study validated the Precision of the designed computer systems. The results showed that the designed computer system based Plug-in technology and GIS simulated hillyslope-gully system gully erosion had higher precision for calculating hillyslope-gully soil erosion. The estimating soil loss precision of the designed computer system was from 93.3% to 99.5% and the average precision was 95.8%, which indicated that the designed computer system for estimating hillyslope-gully soil erosion was feasibility.4. Hillyslope-gully erosion simulation models. This paper analyzed the relations between gully length, width, or depth and rainfall duation by the SPSS, and established empirical model groups of the gully erosion development process, including gully length, width and depth model. All models had high simulated precision after validation based on the observed data, and could meet the reqirements of simulated models. The values of ME were all greater than 0.6 and the R2 in gully length model were all above 0.8. The values of ME were all greater than 0.9 and the R2 in gully length model were all above 0.8. In the most cases, the values of ME were greater than 0.6 and the R2 in gully length model were all above 0.8.5. The visualization system of hillyslope-gully morphological development. Based on the hillyslope-gully erosion simulation model, this paper created 3D model of gully and dynamically simulated the hillyslope-gully erosion development process.
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