三峡库区土壤侵蚀空间分布特征

Spatial distribution analysis of soil erosion in the Three Gorges Reservoir Area

结合三峡库区的区位特征和数据获取条件,对RUSLE模型的因子算法进行相应修正,最后基于GIS评估库区土壤侵蚀风险及其空间分布特征。结果表明:1)库区年均土壤侵蚀量为1亿8 359.43万t/a,平均土壤侵蚀模数为31.85 t/(hm2.a),水土流失面积占库区土地总面积的66.97%;2)库区土壤侵蚀强度与高程梯度间无直接线性关系,中度以上侵蚀主要分布在500～1 500 m高程带上,其中极强烈、剧烈侵蚀在500～1 000 m间出现频率最高,这应该与该区域强烈的人类活动有关;3)库区土壤侵蚀强度与坡度呈显著正相关,中度以上侵蚀在15°以上坡度带的发生频率急剧增加,其53.74%的面积比例贡献了89.06%土壤侵蚀量;4)库区土壤侵蚀强度在不同坡向上表现为半阴坡>正阴坡>半阳坡>正阳坡,阴坡的侵蚀量稍大于阳坡,占库区总侵蚀量的56.63%。说明500～1 500 m高程带、>15°坡度带以及阴坡是库区发生土壤侵蚀的主要区域,也是水土流失防治及治理的重点区域。

In this paper,RUSLE factors algorithms were improved based on environmental characteristics and data availability in the Three Gorges Reservoir Area.Based on GIS technology the improved algorithms were used to evaluate the risk and spatial distribution of soil erosion.The results showed that the annual soil erosion amount and the mean soil erosion modulus in the Three Gorges Reservoir Area were 18 359.43×104 t/a and 31.85 t/（hm2·a）,respectively.The area suffering soil erosion accounted for 66.97% of the reservoir area.There was no direct linear relationship between soil erosion intensity and the altitudinal gradient in Three Gorges Reservoir Area.The area with from moderate to severe erosion intensity mainly distributed in 500-1 500 m elevation zone,which may resulted from the impact of intensive human activities in last decades.The soil erosion intensity was significantly positively correlated with slop gradient.When slope gradient was larger than 15 degree,the frequency of more than moderate erosion increased significantly,The slope area of larger than 15 degree accounted for 53.74% of the reservoir area,but contributed 89.06% of the total soil loss.Soil erosion intensity varied with slope aspects in a trend of semi-shady slopes〉shady slopes〉semi-sunny slopes〉sunny slopes.The amount of soil erosion on shady slopes was slightly higher than that on sunny slopes,accounted for 56.50% of total erosion amount.The results indicated that soil erosion mainly occurred in 500 to 1 500 m elevation zone,slope gradient larger than 15 degree,and shady slopes,which are also the key regions of soil and water loss prevention in Three Gorges Reservoir Area.