Analysis System Development Of Gully Erosion Evolution Of Loess Hilly Region

Quantifying gully erosion evolution is of great significance to understanding of soil erosion process and controlling soil erosion.This thesis studed the extraction methods of the gully parameters based on GIS spatial analysis,builded a spatial database and designed compute system,developed a gully erosion analysis system.Finally,using the observed data by simulating rainfall experiments and LIDAR measuring data,the applicability of the system was evaluated.The main conclusions are as follows:(1)The study proposed the extraction methods of gully parameters(the length,width and depth)using GIS spatital analysis methods.The length was obtained by the overlay analysis of specific profile of gully depth and inclination of gully bottom extracted by the cluster analysis.The average width and the average depth were obtained by grid calculation.(2)Based on Microsoft SQL Server 2005 and GIS spatial database engine,the storage structure of the vector data and the grid data was designed.The spatial database was established based on the design and the LIDAR data was added into the database.(3)With the developing tool of Miscosoft Visual Studio 2008,the system of gully evolution was developed by C#language,using the components of Develope Express 7.0 and SuperMap Objects 6.0.The system had functions of file management,data processing,and gully evolution analysis etc.The developed system could analyze the process of gully erosion development.(4)Using the observed data by simulating rainfall experiments and LIDAR measuring data,the length,width and depth of the gully were obtained by the system.The relative error of the gully length was 5.3%to 9.0%,The relative error of soil loss was 1.1%to 5.3%.The deterministic coefficient(R2)for the relationship between calculated values and measuring data of gully width was above 0.90 and it for gully depth was above 0.85.(5)Characteristics of gully erosion development were expressed as follows:headward erosion deep-cutting of gully channel developed fast in the beginning stage of gully erosion;at the middle term,the headward erosion became weaker;the gully side-wall expanded fast and deep-cutting of gully channel was active;at the later period,the collaping of gully side wall and deep-cutting of gully channel were dominant.Severest gully erosion occurred at 3-5m of slope length in the soil box.With rainfall process,the area of severest gully erosion moved from downslope location to middle slope location.