GIS支持下的澜沧江流域云南段土壤侵蚀空间分析

Spatial analysis on soil erosion of Lancang River Watershed in Yunnan Province under the support of GIS

利用ArcView3.2和ARC/INF08.1软件,通过图层叠加、统计分析和缓冲区分析等,提取西南纵向岭谷区澜沧江流域云南段的不同类型和强度的土壤侵蚀与地形坡度、土地利用/土地覆盖现状、土壤类型和分布、大雨日数以及河流、道路两侧的缓冲区等的相应数据,计算出土壤侵蚀综合度.结果表明,研究区不同坡度等级中,15°～25°坡度上的土壤侵蚀最强,其次为8°～15°坡地和4°～8°坡地;＞25°坡地上则较小;不同用地类型的土壤侵蚀程度不同,总体上,旱耕坡地的土壤侵蚀较草地严重,而草地又较林地严重;在各种土壤类型中,黄壤和石灰土的土壤侵蚀最为突出,其次为红壤、黄棕壤和南方水稻土等;河流两侧和道路两侧的土壤侵蚀都较整个流域要严重,而河流两侧又略重于道路两侧;当多年平均大雨日数小于20日时,土壤侵蚀程度基本上随大雨日数的增加而增加;当大雨日数大于20日时,土壤侵蚀程度反而较小,原因在于前期大雨冲刷侵蚀,带走了地表的疏松物质.研究结果可为有针对性地防治水土流失、减少河流泥沙和水库淤积提供依据.

By map overlapping, statistic analysis and buffer analytical methods, data of soil erosion and terrain slope, land use/land cover situation, soil type and distribution, annual average downfall days, buffer zone of a river and buffer zone of a road in Lancang River drainage area of Yunnan in Southwest China＇s longitudinal mountain range were obtained under the support of Arcview 3.2 and Arc/Info 8.1; then the corresponding soil erosion synthesized indexes of each factor were calculated. The results indicated that. a） In the case of different slope gradients, soil erosion at 15°-25° is the strongest, at 8°-15° and 4°-8° is intermediate and 〉25° is the weakest, b） The order of the descending degrees of soil erosion of different land use types is steep dryland, hilly dryland, middle coverage grassland, mountainous dryland, high cover age grassland, mountainous paddy field, sparse woodland, shrub land, woodland; and in general, erosion on sloping dryland is more serious than that on grassland, and grassland is more serious than woodland, c）Among various soil types, erosion on yellow soil and lime soil is most prominent, besides them are red soil, yellow brown soil, paddy soil, brown soil, dark brown forest soil, laterite soil, brown soil, lateritic red soil and black clay soil. d）Erosion in river buffer and road buffer areas is more serious than that of the entire region, and is a little stronger in river buffer than in road buffer, e） When the number of downfall days is less than 20 annually, soil erosion degree increases along with the increase of downfall days. Whereas when downfall days exceed 20 annually, erosion degree is relatively low because the antecedent rain wash has swept off loose materials on the earth＇s surface. Overall, the result can provide scientific basis for preventing soil and water loss and of reducing river and reservoir sediment.