基于DEM的尼洋河流域地貌形态分析

Analysis of geomorphology of Niyang River Basin based on digital elevation model

尼洋河流域作为雅江重要的支流,域内第一产业发展迅速,然而频繁的地质灾害已严重影响了地区经济的可持续发展。为了对地区灾害成因及易发性的进一步研究提供参考,为防灾减灾建设提供科学依据,以林芝尼洋河流域为例,通过流域数字高程模型(DEM)和其他辅助资料,对流域地貌形态进行深入分析研究。利用GIS的空间分析能力,提取流域坡向、坡度、地形起伏度以及高程等地形因子,制作专题图,并对其与灾害的关联性进行详细分析。结果表明:1)尼洋河流域东、东南、东北、西北向为主要坡度方向;陡坡和陡崖域内面积比例97.06%。2)流域内海拔主要位于≥4000~6000 m,面积比例86.60%,属于高山和极高山;按照地形起伏度分级,其相对高度主要处于≥200~1000 m,比例95.75%,为小起伏和中起伏山地类型。3)域内灾害发生与海拔、坡度、地形起伏度、植被覆盖度、降雨等因素有较大影响,海拔≥3500~5500 m的陡坡中起伏山地、植被覆盖度小、降雨量多的阴坡区域,存在较大潜在危险,危险源片状分布于干流上游和下游、支流中游区域。

[Background]As an important tributary of the Yarlung Zangbo River,the Niyang River plays an important role in the typical disaster occurrence area.In recent years,the first industry in the Niyang River Basin is developing rapidly.However,due to its special geomorphological features,geological disasters in the basin are frequent and have seriously affected the sustainable economic development of the region.The purpose of this study is to reveal the relationship between geological disasters and topography in the Niyang River Basin,and to classify the risks.[Methods]Taking the Niyang River Basin in Linzhi as an example,based on the digital elevation model(DEM)and other auxiliary data,the topographic factors such as slope direction,slope,terrain fluctuation and elevation were extracted,the GIS was used to produce the thematic maps.[Results]1)In the Niyang River Basin,the east,southeast,northeast and northwest directions are the main slope directions;the steep slope area is the largest,accounting for 85.98%,followed by the steep cliff,accounting for 11.08%of the area,which is 3.8 times of the gentle slope area.The>25°-45°is a prone area for landslide disasters,the area in the basin accounts for 50.88%,areas with a slope<25°can be used as cultivated land and is 6624.19 km2,accounting for 38.03%.2)The Niyang River Basin is divided into 4 categories according to the mountain elevation:low mountains,median mountains,high mountains and great high mountains.The elevation of the basin is mainly located at≥4000-6000 m,accounting for 86.60%of the area,belonging to high mountains and great high mountains.According to the terrain fluctuation,the relative height is mainly in the range of≥200-1000 m,and the area is 17103.54 km2,accounting for 95.75%,which belongs to the small and median undulating mountains.3)Altitude,slope,terrain fluctuation,vegetation coverage,rainfall and other factors have a great impact on the occurrence of disasters.The areas of steep slopes with an altitude of≥3500-5500 m,median undulating mountains,small vegetation coverage and heavy rainfall have a large potential risk,and the dangerous sources are distributed in the upper and lower reaches of the main stream and in the middle part of the tributary.[Conculsions]The occurrence of geological disasters is closely related to the regional topography.Altitude,slope,terrain fluctuation,vegetation coverage,rainfall and other factors have a great impact on the occurrence of disasters in the Niyang River Basin.This study may provide reference for further research on the causes and susceptibility of regional disasters,and provide a scientific basis for disaster prevention and mitigation.