ESTIMATION AND PREDICTION OF THE SOIL EROSION RISK INFLUENCED BY THE URBANIZATION PROCESS WITHIN A COUNTY IN HILLY AREA OF SOUTHEAST CHINA, USING RUSLE AND CLUES MODEL

Soil erosion by water is a well-known environmental problem. Urbanization is a worldwide trend, leading to a drastic change of land use forms in local areas, and change in soil erosion risks. This research analyzed the soil erosion risks in the past two decades of Zhuji County, which is located in hilly area of Southeast China and is experiencing fast urbanization process, to evaluate the influence of the urbanization on soil erosion using Revised Universal Soil Loss Equation (RUSLE). Land use maps were developed by using CLUEs (the Conversion and Land Use and its Effect at Small regional extent) model to estimate the soil erosion risk in 3 different urbanization scenarios of 2020. The results showed that, during 1984 to 2009, as the percentage of the urban and built-up area increased from 0.43% to 10.95%, though the extreme erosion value did not have a clear trend, from 1984 to 2004, the percentage of area with soil erosion risk higher than medium level kept increasing from 3.23% to 6.34%, the percentage of area with tolerable soil erosion risk was decreasing from 71.57% to 67.58%. The scenario analysis showed that the change of the urban and built-up area would change the soil erosion risk significantly, especially the high and severe level erosion risk. Higher than medium level soil erosion risk is 7.49% in Scenario 1 with 15.33% urban and built-up area, 8.63% in Scenario 2 with 18.86% urban and built-up area, and 13.07% in Scenario 3 with 25% urban and built- up area. And the buffer zone analysis of a highway in the county also showed that the soil erosion risk correlated with the size of urban and built-up area. These results indicated that Zhuji County needs to pay more attention when urbanize in hilly area since it leads to more severe erosion risk without prevention measurements. And policies should balance the preservation of the agriculture land and the potential soil erosion risk during urbanization process.