南雄县位于北江上游,水土流失面积40万亩,占土地总面积11.1%,其中紫色砂页岩侵蚀区17.97万亩(沟状流失8.4万亩,坡耕地流失9.57万亩),其余属红色砂砾岩和花岗岩发育的红壤侵蚀区22万亩。据调查,全县平均每年流失泥沙198万立米,其中流入渍江河的达136万立米。1957年以前二十年间,河床淤高二米,平均每年淤高10厘 Nanxiong County is located in the upper reaches of Beijiang River with an area of ​​400000 mu of soil erosion and 11.1% of the total land area, of which 179,700 mu of purple sand shale erosion area (84,000 mu of ditch drainage and 95,700 mu of slope farmland loss) Glutenite and granite red soil erosion area of ​​22 acres. According to the survey, the county lost an average of 1.98 million cubic meters of sediment every year, of which 1.36 million cubic meters were infused into the river. During the two decades before 1957, the silt of the riverbed was two meters high, with an average siltation of 10% per year