The Impact Of The Spatial Distribution Pattern Of Land Use On Runoff And Sediments' Process

Soil erosion is the most serious ecological environmental problem in Loess Plateau of China. Unreasonable land use practice is identified as one of the most important reasons for triggering and aggravating soil erosion, and the driving mechanisms for land use change and the relationship between land use spatial pattern and soil erosion are the important aspects for the study about soil erosion. By integrating GIS, social and economic statistical and field investigating data, taking Wudinghe River watershed as the case study area, we discussed the driving mechanisms for the watershed land use change and the relationship between land use spatial distribution pattern and soil erosion at different scales. The results as follows:1. From 1980's to 1990's, different land use area and land use spatial pattern had changed relatively dramatically in the representative region of the Wudinghe watershed, Yulin region, especially for the northwest part, where land use pattern changed from farmland and forest as a major characteristic to forest and grassland.2. The major driving factors for farmland change in Yulin region are total population, the average farmer income and the proportion of agricultural labors, and there is a negative correlation between farmland area and the factors including total population, total crop production, total rural social production value and total social input.3. The topography was a decisive factor for the spatial distribution pattern of land use, and the study scale also have some impacts on it. The region in the sand region had a totally different general characteristic for land use spatial distribution pattern from the region in hilly and ravine region, and the pattern also had some variation at different scales.4. There was a strong consistency between runoff variation and sediment variation. There was no direct correlation between runoff module and erosion module, but there was an obvious consistency between runoff module variation and erosion module variation. The catchments with large runoff module variation also had a large erosion module variation.5. The land use spatial distribution pattern had a decisive impact on the inter-year variation characteristics of both runoff and sediment. The catchments, which had even land use spatial distribution, had small inter-year variation of both runoff and sediment, and vice versa.6. The impact of the spatial distribution pattern of land use on runoff and sediments would differ at different catchments scales. Comparing the catchments with the same conditions at the same scales, we found that at the small scale catchments, the factor directly impacting the runoff variation and sediment variation was the relative distribution location at sloping fields, and at the median scale catchments, was the slope distribution of land use components, while at the large scale catchments, the distance distribution of land use components. Comparing the catchments at different scales, we found that there was a common characteristic between catchments at different scales, that the more uneven the spatial distribution of land use was, the larger runoff variation and sediment variation in the corresponding catchments were.