那曲地区融水侵蚀引起沉积的影响因素

Influence factors of deposition induced by melt water erosion in Naqu region,China

冰川、积雪融水形成的融水侵蚀是高海拔寒区土壤侵蚀的重要形式.本文对那曲地区融水侵蚀引起沉积的影响因素进行研究,提出以沉积扇面积比例作为指标反映融水侵蚀引起沉积的强弱.基于GIS空间叠加分析确定最小图斑,通过逐步回归分析,建立融水侵蚀引起沉积的影响因素回归方程,确定融水侵蚀引起沉积的主要影响因素.结果表明:那曲地区境内分布大量扇形地;不同地区分布差异明显,那曲地区扇形地集中在中部缓坡地区;扇形地多分布在山谷出口处,多数规模较大,且面积、厚度变化很大.风速、归一化植被指数(NDVI)、土壤可蚀性K值、气温年较差和陡坡面积比是研究区融水侵蚀引起沉积的主要影响因素,其中,融水侵蚀引起的沉积与风速和NDVI呈正相关关系,与K值、气温年较差和陡坡面积比呈负相关关系.

Melt water erosion is one of the important soil erosion forms caused by the melt water from glacier and snow in high altitude cold areas of China. This paper investigated the influencing factors of deposition caused by melt water erosion in Naqu region. Alluvial fan ratio was presented as an index to characterize the degree of the deposition induced by melt water erosion. Minimum poly- gon was determined based on spatial overlay technology of Geographic Information System （GIS）. The regression equation between the deposition index and the influencing factors was established through the stepwise regression analysis based on minimum polygon. Key influencing factors were identified according to the stepwise regression equation. The results showed that large amounts of alluvial fan were observed in Naqu region; extensive alluvial fans were centered at gentle slope areas in the central part of Naqu region with great spatial differences; alluvial fans were mainly dis- tributed at valley exits, most of which were at large scale with vast differences in area and thickness. Wind speed, normalized difference vegetation index （NDVI） , K value of soil erodibility, annual temperature range and the steep slope area ratio were identified as the key influencing factors on the deposition induced by melt water erosion in the studied area. Index of deposition was positively cor- related with the wind speed and NDVI, and showed negative relationships with the K value of soil erodihility, the annual temperature range and steep slope area ratio.