Study On Types And Intensity Gradation Of Urban Soil And Water Loss In The Pearl River Delta

The problem of urban soil and water loss is a new subject in soil and water conservation field, and the stucly of loss types and intensity gradation is a weak link in present research. On the basis of a definition of urban soil and water loss, the paper made a preliminary study on its types and intensity gradation of the Pearl River Delta, which aims at revealing the essence and laws of urban soil and water loss, ensuring for the scientific and standardized classification and gradation in urban soil water loss and bringing about further research in this field and at the same time provides a reference for investigation, regional divisions and control measures of urban soil and water loss in the Pearl River Delta. The main contents and conclusions of the paper are as follows.1. Starting from the analysis on spatial limits and influencing factors, urban soil and water loss is defined as the loss which happens in and around urban built-up areas, caused by human activities in urban development and construction in the course of urbanization.2. The analysis on types of soil and water loss in the Pearl River Delta and the comparison with types of the other regions of Guangdong province show that soil and water loss in the Pearl River Delta is more obviously influenced by human activities especially by urban development and construction.3. Correlation analysis indicates that the types whose proportion of area to total area of man-made soil and water loss are positively correlated with economic development level are erosion caused by quarrying and digging earth, erosion caused by constructing development area and erosion caused by constructing water conservancy and hydro- power project. The types whose proportion of area to total area of man-made soil and water loss are negatively correlated with economic development level are erosion caused by mining, erosion caused by reclaiming on steepinStudy on Types and Intensity Gradation of Urban Soil and Water Loss in the Pearl River Deltaslop(slop above 25?, erosion caused by constructing highway and railway, erosion caused by cultivating on slope field (slop below 25? and erosion caused by the other human activities. Considering that positive correlation coefficient between proportion of erosion area caused by constructing water conservancy and hydro- power project and economic development level is small, and area of this erosion is also small in the Pearl River Delta, and water conservancy and hydro-power project is mainly conducted in mountain countryside, the type of erosion is not included within the categories of urban soil and water loss of the Pearl River Delta; Considering again that negative correlation coefficient between proportion of erosion area caused by constructing highway and railway and economic development level is small, and proportion of this erosion area decreases apparently with the decrease of economic development and urbanization level from the Pearl River Delta to Guangdong province to the other regions of Guangdong province, erosion caused by constructing highway and railway is put under the categories of urban soil and water loss in the Pearl River Delta in this paper.According to the result stated above and the principles of determining the types of urban soil and water loss, the paper divides urban soil and water loss of the Pearl River Delta into three types, in terms of the way of urban construction activities, i. e. erosion caused by constructing development area, erosion caused by quarrying and digging earth and erosion caused by constructing highway and railway.4. The erosion features, spatial distribution and temporal change of the three types of urban soil and water loss in the Pearl River Delta are systemically expounded in this paper.5. The erosion modulus of urban soil and water loss in the Pearl River Delta is big and its variation range is especially great, so, present intensity gradation criteria of soil and water loss (including urban soilIVStudy on Types and Intensity Gradation of Urban...