Characteristics of landslide in Koshi River Basin,Central Himalaya

Koshi River basin, which lies in the Central Himalayas with an area of 71,500 km2, is an important trans-boundary river basin shared by China, Nepal and India. Yet, landslide-prone areas are all located in China and Nepal, imposing alarming risks of widespread damages to property and loss of human life in both countries. Against this backdrop, this research, by utilizing remote sensing images and topographic maps, has identified a total number of 6877 landslides for the past 23 years and further examined their distribution, characteristics and causes. Analysis shows that the two-step topography in the Himalayan region has a considerable effect on the distribution of landslides in this area. Dense distribution of landslides falls into two regions: the Lesser Himalaya(mostly small and medium size landslides in east-west direction) and the TransitionBelt(mostly large and medium size landslides along the river in north-south direction). Landslides decrease against the elevation while the southern slopes of the Himalayas have more landslides than its northern side. Change analysis was carried out by comparing landslide distribution data of 1992, 2010 and 2015 in the Koshi River basin. The rainfallinduced landslides, usually small and shallow and occurring more frequently in regions with an elevation lower than 1000 m, are common in the south and south-east slopes due to heavy precipitation in the region, and are more prone to the slope gradient of 20°~30°. Most of them are distributed in Proterozoic stratum(Pt3ε, Pt3 and Pt2-3) and Quaternary stratum. While for earthquake-induced landslides, they are more prone to higher elevations(2000~3000 m) and steeper slopes(40°~50°).

Land use and land cover change within the Koshi River Basin of the central Himalayas since 1990

Land change is a cause and consequence of global environmental change.Land use and land cover have changed considerably due to increasing human activities and climate change,which has become the core issue of major international research projects.This study interprets land use and land cover status and the changes within the Koshi River Basin(KRB)using Landsat remote sensing(RS)image data,and employs logistic regression model to analyze the influence of natural and socioeconomic driving forces on major land cover changes.The results showed that the areas of built-up land,bare land and forest in KRB increased from 1990 to 2015,including the largest increases in forest and the highest growth rate in construction land.Areas of glacier,grassland,sparse vegetation,shrub land,cropland,and wetland all decreased over the study period.From the perspective of driving analysis,the role of human activities in land use and land cover change is significant than climate factors.Cropland expansion is the reclamation of cropland by farmers,mainly from early deforestation.However,labor force separation,geological disasters and drought are the main factors of cropland shrinkage.The increase of forest area in India and Nepal was attributed to the government’s forest protection policies,such as Nepal’s community forestry has achieved remarkable results.The expansion and contraction of grassland were both dominated by climatic factors.The probability of grassland expansion increases with temperature and precipitation,while the probability of grassland contraction decreases with temperature and precipitation.

Assessment of Changes in the Value of Ecosystem Services in the Koshi River Basin,Central High Himalayas Based on Land Cover Changes and the CA-Markov Model

Climate warming and economic developments have created pressures on the ecological systems that human populations rely on,and this process has contributed to the degradation of ecosystems and the loss of ecosystem services.In this study,Landsat satellite data were chosen as the data source and the Koshi River Basin（KB） in the central high Himalayas as the study area.Changes in land cover and changes in the value of ecosystem services between 1990 and 2010 were analyzed and the land cover pattern of the KB in 2030 and 2050 was modeled using the CA-Markov model.Changes in land cover and in the value of ecosystem services in the KB for the period 2010–2050 were then analyzed.The value of ecosystem services in the KB was found to decrease by 2.05×10~8 USD y^（-1） between 1990 and 2010.Among these results,the services value of forest,snow/glacier and barren area decreased,while that of cropland increased.From 1990 to 2050,forest showed the largest reduction in ecosystem services value,as much as 11.87×10~8 USD y^（-1）,while cropland showed the greatest increase,by 3.05×10~8 USD y^（-1）.Deforestation and reclamation in Nepal contributed to a reduction in the value of ecosystem services in the KB.Barren areas that were transformed into water bodies brought about an increase in ecosystem services value in the lower reaches of the Koshi River.In general,this process is likely to be related to increasing human activity in the KB.

Land Cover Status in the Koshi River Basin,Central Himalayas

The Koshi River Basin is in the middle of the Himalayas,a tributary of the Ganges River and a very important cross-border watershed.Across the basin there are large changes in altitude,habitat complexity,ecosystem integrity,land cover diversity and regional difference and this area is sensitive to global climate change.Based on Landsat TM images,vegetation mapping,field investigations and 3S technology,we compiled high-precision land cover data for the Koshi River Basin and analyzed current land cover characteristics.We found that from source to downstream,land cover in the Koshi River Basin in 2010 was composed of water body（glacier）,bare land,sparse vegetation,grassland,wetland,shrubland,forest,cropland,water body（river or lake） and built-up areas.Among them,grassland,forest,bare land and cropland are the main types,accounting for 25.83%,21.19%,19.31% and 15.09% of the basin＇s area respectively.The composition and structure of the Koshi River Basin land cover types are different between southern and northern slopes.The north slope is dominated by grassland,bare land and glacier;forest,bare land and glacier are mainly found on northern slopes.Northern slopes contain nearly seven times more grassland than southern slopes;while 97.13% of forest is located on southern slopes.Grassland area on northern slope is 6.67 times than on southern slope.The vertical distribution of major land cover types has obvious zonal characteristics.Land cover types from low to high altitudes are cropland,forest,Shrubland and mixed cropland,grassland,sparse vegetation,bare land and water bodies.These results provide a scientific basis for the study of land use and cover change in a critical region and will inform ecosystem protection,sustainability and management in this and other alpine transboundary basins.

Vertical distribution changes in land cover between 1990 and 2015 within the Koshi River Basin,Central Himalayas

The study of mountain vertical natural belts is an important component in the study of regional differentiation.These areas are especially sensitive to climate change and have indicative function,which is the core of three-dimensional zonality research.Thus,based on high precision land cover and digital elevation model(DEM)data,and supported by MATLAB and ArcGIS analyses,this paper aimed to study the present situation and changes of the land cover vertical belts between 1990 and 2015 on the northern and southern slopes of the Koshi River Basin(KRB).Results showed that the vertical belts on both slopes were markedly different from one another.The vertical belts on the southern slope were mainly dominated by cropland,forest,bare land,and glacier and snow cover.In contrast,grassland,bare land,sparse vegetation,glacier and snow cover dominated the northern slope.Study found that the main vertical belts across the KRB within this region have not changed substantially over the past 25 years.In contrast,on the southern slope,the upper limits of cropland and bare land have moved to higher elevation,while the lower limits of forest and glacier and snow cover have moved to higher elevation.The upper limit of alpine grassland on the northern slope retreated and moved to higher elevation,while the lower limits of glacier and snow cover and vegetation moved northward to higher elevations.Changes in the vertical belt were influenced by climate change and human activities over time.Cropland was mainly controlled by human activities and climate warming,and the reduced precipitation also led to the abandonment of cropland,at least to a certain extent.Changes in grassland and forest ecosystems were predominantly influenced by both human activities and climate change.At the same time,glacier and snow cover far away from human activities was also mainly influenced by climate warming.

基于地学信息图谱的科西河流域滑坡空间分异研究

以科西河流域滑坡为例,对滑坡信息图谱的概念和内容进行研究,归纳滑坡信息图谱由条件图谱、编目图谱、风险分布图谱和风险管理图谱组成,提出滑坡信息图谱按表达内容和功能的分类方法。基于滑坡条件图谱与编目图谱,采用空间统计的方法,揭示了研究区滑坡垂直向和纬度向分布与演化的空间分异规律:滑坡在垂直向200~1 000 m的高程段内为数量高密度区,400~1 200 m和2 800~3 600 m高程段面积比例大,北纬26°42′00″N~26°48′00″N为数量高密度区,26°42′00″N~26°48′00″N和27°24′00″N~27°30′00″N滑坡面积比例较大;相比1992年滑坡,新增滑坡在垂直向200~1 000 m和2 800~3 600 m高程段数量密度高,在3 200~3 400 m高程段面积比例较大,北纬26°48′00″N~26°54′00″N和27°48′00″N~27°54′00″N为高数量密度区,27°24′00″N~27°42′00″N为高面积比例区。

1990—2020年科西河流域冰川冰湖遥感监测

科西河流域冰川和冰湖较为发育,随着全球气候变暖,冰川融水成为冰湖扩张的重要补给,同时会引发冰湖溃决洪水(GLOF)等自然灾害,给当地居民生产生活带来巨大损失。因此,对该区域冰川冰湖的时空分布规律和变化特征的研究具有现实意义。本文基于Landsat系列遥感影像和数字高程模型,分析了1990—2020年科西河流域冰川冰湖面积时空分布与变化特征,并结合气象格点数据和GLOF事件,探究科西河流域冰川冰湖对气候变化响应及其与GLOF事件关系。结果表明:(1)1990—2020年科西河流域冰川面积呈加速退缩的趋势,近10年加速退缩趋势进一步加强。(2)科西河流域冰川主要分布在海拔4800~6800 m范围内,而在坡度上,主要分布在5°~20°。(3)1990—2020年科西河流域冰湖呈加速扩张的趋势,冰湖面积共扩张了26.09 km^(2),其中面积>0.25 km^(2)的冰湖扩张迅速;与冰川相连的冰湖面积扩张显著,面积增长率为49.39%。(4)1990—2020年科西河流域共11条冰湖发生溃决,溃决冰湖分布面积较小,介于0.02~0.7 km^(2)。(5)1990—2020年科西河流域气温和降水量呈波动增长趋势,降水增加不足以弥补温度引起的冰川退缩,致使科西河流域冰川加速退缩,冰湖加速扩张,冰湖溃决事件频发。

1967-2014年科西河流域冰湖时空变化

冰湖是高山寒区气候变化的灵敏指示器和诱发山地溃决洪水或泥石流的灾害源。基于1960s-2010s多源遥感影像数据(Corona、Landsat MSS/TM/ETM+OLI)、地形图、冰川编目和气象数据,利用RS和GIS技术综合分析科西河流域近50年冰湖(≥0.05 km^2)时空变化特征及其对冰川变化影响。研究结果表明:(1)近50年来科西河流域冰湖整体经历了"先平稳后扩张"的过程,其中1960s至1980s初期,科西河流域有37个冰湖消失,但总面积趋于平稳状态;1980s中期至2010s初期,流域内冰湖规模迅速扩张,且2000s之后冰湖扩张速率明显加快,至2010s初期增加为321个冰湖(88.43 km^2)。(2)科西河流域冰湖集中分布于海拔5000-5500 m,面积小于0.25 km^2的小规模冰湖占总数量的74.45%,而面积大于1 km^2和介于0.05-0.25 km^2的冰湖占总面积的64.18%。(3)除利库科拉(Likhu Khola)流域外,科西河流域其他5个子流域冰湖均呈扩张趋势,其中尤以阿润(Arun)流域冰湖扩张最为显著。(4)气候变暖及其引发的冰川退缩是科西河流域冰湖扩张的根本原因,当冰川末端伸入冰湖时,冰水物质与能量交换在一定程度上加速了冰川消融与退缩。

基于遥感和GIS的喜马拉雅山科西河流域冰湖变化特征分析

受全球气候变暖的影响,冰川退缩,冰湖数量增多和面积增大被认为指示气候变化的重要依据,冰湖面积增大导致其潜在危险性增大.因此,研究冰湖的变化对于气候变化和冰湖灾害研究具有重要意义.基于Landsat TM/ETM＋遥感影像采用人工解译的方法,获取了喜马拉雅山地区科西河流域1990年前后、2000年和2010年的冰湖数据,并对冰湖面积〉0.1 km^2且一直存在的199个冰湖的面积和长度变化进行对比分析.结果表明：科西河流域内面积〉0.1 km^2的冰湖的面积呈现增加趋势,1990年冰湖面积为73.59 km^2,2010年冰湖面积增加至86.12 km^2.科西河流域内喜马拉雅山南北坡冰湖变化存在差异,喜马拉雅山北坡变化较大的冰湖主要分布在海拔4 800-5 600 m之间,而南坡变化较大的冰湖主要分布在海拔4 300-5 200 m之间;喜马拉雅山北坡的冰湖有65%的冰湖表现扩张,且扩张冰湖的面积主要是由冰湖在靠近终碛垅的一端基本不发生变化,而仅在靠近冰川一端发生变化贡献的;喜马拉雅山南坡的冰湖有32%的冰湖变化表现扩张,且扩张的冰湖面积主要来自于冰面湖扩张.在科西河流域内,位于喜马拉雅山北坡的冰湖平均变化速度略高于南坡的冰湖平均变化速度.

尼泊尔山区水资源可利用性与农户生计适应链框架研究——以柯西河流域为例

尼泊尔山区农业用水以雨水和山泉水(地下水)为主,灌溉设施普遍匮乏。在全球气候变化影响下,极端天气过程不断呈现,长期干旱和短时暴雨对农业生产的影响日益严重,直接影响农户生计安全,特别是纯农型的农户,面临更多的生计适应性挑战。柯西河(Koshi River)发源于中国西藏,流经尼泊尔进入印度,其流域的中上游至中下游是尼泊尔重要的农区,农业水资源的可利用性非常重要。通过统计分析法和生计适应链框架相结合,分析科西河流域水资源可用性,阐明科西河流域水资源变化特征,解决农户生产和生活用水问题,针对农户生计潜在水危机风险,提出农户生计适应性链框架及适应对策。

喜马拉雅山中段柯西河跨境流域河流沉积物的矿物和元素特征

本文测定了柯西河流域中尼跨境河段23个河床表层沉积物样品的矿物组分及微量元素含量。结果表明,上、下游沉积物中长石/石英比分别为0.55和0.37,碳酸盐矿物分别以方解石(12%)和白云石(3%)为主,反映上游化学风化强度小于下游;上下游微量元素Zr、Hf、Cs、Li的分布差异与源岩及河流分选作用有关;与其他发源于青藏高原的河流相比,科西河沉积物中∑REE含量总体较高,主要受源区重矿物影响,其中上游∑REE低于下游,与河流分选造成的重矿物分布有关;LREE明显富集及δEu负异常(0.3~0.59)指示沉积物为长英质物源,结合微量元素图解和富集因子分析表明沉积物主要来源于花岗片麻岩,受人为影响较小。

柯西河流域植被覆被变化特征及其土地利用背景分析

植被作为陆地生态系统的重要组成部分,其动态变化对于定量评估区域生态环境质量具有重要意义。本文以典型跨境流域--柯西河流域为例,基于2000-2017年MODIS-NDVI时序数据及土地利用数据,运用Mann-Kendall统计检验和Sen’s趋势等方法分析该区域植被覆被的时空演变特征,并探讨该变化的土地利用背景。结果表明:(1)柯西河流域植被覆被空间分布差异明显,且NDVI值呈现"双峰"结构;(2)2000-2017年柯西河流域植被覆被整体呈现增加趋势,但存在着一定的空间分异。区域尺度上,中国境内、印度境内和尼泊尔境内植被均呈上升趋势,但变化幅度差异明显,表现为印度>尼泊尔>中国;像元尺度上,植被改善的地区占整个研究区的87.74%,主要分布于中国境内中部地区和尼泊尔境内中、南部地区以及印度境内的部分区域;NDVI趋于降低的区域占整个研究区的12.26%,主要集中于尼泊尔境内的加德满都地区及主要公路沿线和河流沿岸地区;(3)植被变化趋势与地形因子(高程、坡度、坡向)显著相关,其空间分布表现出明显的地形指向性;(4)植被变化显著区域与土地利用变化典型地区高度一致。裸地和水体的转化导致局部植被覆被升高;耕地和林地的转化导致局部地区植被覆被降低。研究结果可为柯西河流域土地利用政策的制定、生态环境的保护与建设、植被恢复及可持续发展提供一定的参考。

南亚典型国际河流柯西河流域土地覆被空间分布特征

作为南亚极为重要的跨境河流,柯西河横跨中国、尼泊尔、印度三国。流域内部海拔落差巨大,土地覆被类型多样,生态系统完整,是研究土地覆被及全球气候变化的敏感区之一。将土地利用本底数据叠加DEM和TRMM3B43详细分析了柯西河流域土地覆被类型的结构和空间分布特征,并进一步分析了该流域土地覆被类型与地形、气象因子之间的相关性。结果表明:①柯西河流域土地覆被类型可分为裸地、林地、灌木、旱地、水田、建筑用地、河流、湖泊、冰川/永久积雪、河漫滩、盐碱地、人工园地、沼泽地、草地共14类,其中水田面积最大,约占流域总面积的32.56%,其次是林地占18.89%;②地形因子对土地覆被类型影响巨大,由南向北随着地形的起伏,主要土地覆被类型依次表现为水田、林地、旱地、灌木、裸地、冰川、草地的垂直地带性;③土地覆被类型与气候因子相关性较强,随着降雨量由少变多,土地覆被优势类型依次表现为裸地、草地、灌木、冰川/永久积雪、林地、水田。开展柯西河流域的土地覆被研究对该流域土地资源合理利用、生态环境保护具有重要的理论和实践意义,同时也能为中国倡导的"一带一路"国际区域经济合作战略提供基础数据保障。

柯西河流域森林覆盖度的空间分布及变化分析

森林是陆地生态系统的重要组成部分,对改善生态环境、维护生态平衡具有不可替代的作用。本文以柯西河流域为研究区,采用Global Forest Watch数据,通过空间叠加分析、转移矩阵等方法,分析研究区内不同地形因子森林覆盖度的分布及变化特征。结果表明:1)研究区森林以中森林覆盖度为主,占研究区森林总面积的31.16%,不同的森林覆盖度占森林总面积的比例基本差别不大;森林覆盖度随海拔和坡度的增加呈现先增加后减少的趋势,其中,森林覆盖度随着海拔变化趋势更显著;森林覆盖度随坡向变化为西北坡>北坡>东北坡>西坡>东坡>西南坡>东南坡>南坡;2)从2000年到2010年柯西河流域森林的总面积增加了651.28 km^2,不同的森林覆盖等级之间均发生了相互转移,从转出来看,变化最为显著的为中高森林覆盖度,转出面积为3171.66 km^2,从转入来看,中森林覆盖度的转入面积最大,为3652.00 km^2;3)从2000年到2010年稳定区占据一定的优势地位,森林覆盖度减少的区域面积为7325.68 km^2,森林覆盖度增加的区域面积为5352.25 km^2,森林覆盖度增加的区域小于减少的区域;4)不同因子对森林覆盖度的变化具有不同的影响,但是,森林覆盖度减少的面积大于增加的面积。

1967–2014年科西河流域面积≥0.05 km2冰湖轮廓数据集

科西河流域发育有众多的冰川和冰湖,冰川覆盖率达9.78%,冰湖数量221个,冰湖分布及变化不仅是预测该区域冰湖溃决洪水灾害的基础数据,而且可以在一定程度上反映高山寒区气候及冰川水资源的变化。本数据集应用1960s–2010s多源遥感影像数据(Corona、Landsat MSS/TM/ETM+/OLI)及地形图进行目视解译获得了科西河流域1960s、1970s、1980s、1990s、2000s和2010s的6期冰湖数据,解译精度控制在一个像元以内。研究区空间范围为26.86°–29.14°N,85.39°–88.95°E,覆盖印德拉瓦迪、孙科西、绒辖曲、利库科拉、牛奶河、阿润和塔木尔等子流域。本数据集包括科西河流域内面积≥0.05 km2的冰湖,数据集时序较长且包含冰湖类型及其他几何属性信息,可作为科西河流域冰湖时空变化、冰湖水量变化评估的基础数据,也可作为喜马拉雅山地区冰湖溃决危险性评估、水资源变化、气候变化及冰湖与冰川间变化响应关系等研究的重要依据。

1971-2009年珠穆朗玛峰地区尼泊尔境内气候变化

利用珠穆朗玛峰南坡尼泊尔境内(科西河流域)的10个气象站1971-2009年月平均气温、月平均最高、最低气温和逐月降水资料,采用线性趋势、Sen斜率估计、Mann-Kendall等方法分析区域气候变化状况及其时空特征,并与珠穆朗玛峰北坡地区气候进行比较,分析了珠穆朗玛峰地区气候变化的特征与趋势。结果表明:(1)1971-2009年间,珠穆朗玛峰南坡年平均气温为20.0℃,线性升温率为0.25℃/10a,与北坡主要受年平均最低气温影响相反,增幅主要受年平均最高气温升高的影响,并且在1974年及1992年间出现两次显著增温,增温特别明显的月份为2月和9月;(2)该地区降水变化的局地性较强,近40年间年平均降水量为1729.01mm,年平均降水量以每年约4.27mm的线性增幅有所增加,但并不显著,且降水月变化和季变化特征均不明显;(3)由于珠穆朗玛峰南坡受到季风带来暖湿气流和喜马拉雅山阻挡的双重影响,珠峰南坡的年平均降水量远高于北坡;(4)珠穆朗玛峰南坡气温变暖的海拔依赖性并不明显,且南坡地区的变暖趋势并没有北坡变暖趋势明显。

Climate change on the southern slope of Mt. Qomolangma （Everest） Region in Nepal since 1971

Based on monthly mean, maximum, and minimum air temperature and monthly mean precipitation data from 10 meteorological stations on the southern slope of the Mt. Qomolangma region in Nepal between 1971 and 2009, the spatial and temporal characteristics of climatic change in this region were analyzed using climatic linear trend, Sen＇s Slope Estimates and Mann-Kendall Test analysis methods. This paper focuses only on the southern slope and attempts to compare the results with those from the northern slope to clarify the characteristics and trends of climatic change in the Mt. Qomolangma region. The results showed that： （1） between 1971 and 2009, the annual mean temperature in the study area was 20.0℃, the rising rate of annual mean temperature was 0.25℃/10a, and the temperature increases were highly influenced by the maximum temperature in this region. On the other hand, the temperature increases on the northern slope of Mt. Qomolangma region were highly influenced by the minimum temperature. In 1974 and 1992, the temperature rose noticeably in February and September in the southern region when the increment passed 0.9℃. （2） Precipitation had an asymmetric distribution; between 1971 and 2009, the annual precipitation was 1729.01 mm. In this region, precipitation showed an increasing trend of 4.27 mm/a, but this was not statistically significant. In addition, the increase in rainfall was mainly concentrated in the period from April to October, including the entire monsoon period （from June to September） when precipitation accounts for about 78.9% of the annual total. （3） The influence of altitude on climate warming was not clear in the southern region, whereas the trend of climate warming was obvious on the northern slope of Mt. Qomolangma. The annual mean precipitation in the southern region was much higher than that of the northern slope of the Mt. Qomolangma region. This shows the barrier effect of the Himalayas as a whole and Mt. Qomolangma in particular.

尼泊尔柯西河流域土地利用/覆被变化影响下的土壤流失量与输沙量的动态变化

How the dynamics in soil loss(SL) and sedimentation are affected by land use/cover change(LULCC) has long been one of the most important issues in watershed management worldwide, especially in fragile mountainous river basins. This study aimed to investigate the impact of LULCC on SL and sediment export(SE) in eastern regions of the Koshi River basin(KRB), Nepal, from 1990 to 2021. The Random Forest classifier in the Google Earth Engine platform was employed for land use/land cover(LULC) classification, and the Integrated Valuation Ecosystem Services and Trade-offs(InVEST) Sediment Delivery Ratio model was used for SL and SE modeling. The results showed that there was a pronounced increase in forest land(4.12%), grassland(2.35%), and shrubland(3.68%) at the expense of agricultural land(10.32%) in KRB over the last three decades. Thus, the mean SL and SE rates decreased by 48% and 60%, respectively, from 1990 to 2021. The conversion of farmland to vegetated lands has greatly contributed to the decrease in SL and SE rates. Furthermore, the rates of SL and SE showed considerable spatiotemporal variations under different LULC types, topographic factors(slope aspect and gradient), and sub-watersheds. The higher rates of SL and SE in the study area were observed mostly in slope gradient classes between 8° and 35°(accounting for 83%–91%) and sunny and semi-sunny slope aspects(SE, S, E, and SW)(accounting for 57%–65%). Although the general mean rate of SL presented a decreasing trend in the study area, the current mean SL rate(23.33 t ha^(-1)yr^(-1)) in 2021 is still far beyond the tolerable SL rate of both the global(10 Mg ha^(-1)yr^(-1)) and the Himalayan region(15 t ha^(-1)yr^(-1)). Therefore, landscape restoration measures should be integrated with other watershed management strategies and upscaled to hotspot areas to regulate basin sediment flux and secure ecosystem service sustainability.

柯西河流域

柯西河发源于喜马拉雅山脉中部希夏邦马峰北坡的达索普冰川,自喜马拉雅山北侧,穿过整个山体,南至恒河平原,跨中国、尼泊尔和印度3国,是恒河重要的支流,也是南亚地区重要的跨界河流。柯西河流域水系主要由西支的孙科西河、北支的阿润河和东支的塔姆尔河等3条支流构成[1-4]。

基于GIS的雪崩对冰湖风险性评估——以喜马拉雅山科西河流域为例

雪崩是冰湖风险性评估的因子之一，借鉴欧美发展起来的雪崩模型，在冰湖溃决洪水频发的喜马拉雅山地区开展雪崩对冰湖风险性评估研究具有重要意义。基于ICIMOD IKONOS DEM和Landsat—TM数据，利用GIS方法提取了研究区雪崩形成的海拔、平面曲率、坡度和地表覆盖类型等估算因子，根据Av=（Al＋Fy）×S×Rg模型估算了研究区潜在雪崩形成区域，并应用GIS方法和α-β模型估算了雪崩的传播路径。结果表明：潜在雪崩不易形成的“低”值多分布在谷底及地表覆盖类型为密林的山坡上，而“高”、“较高”值多分布在坡度为30°-50°、地表类型以裸岩或草地为主的山坡和冰川上，这些分布符合雪崩形成的客观实际；分析判断发现研究区内“高”值区域，也就是潜在雪崩形成区共有98处，其中有10处能够进入冰湖，对这些冰湖的稳定性造成风险，这意味着在分析研究区所有冰湖的溃决风险性时，只有受到潜在雪崩影响的9个冰湖需要考虑雪崩因素，其余冰湖在冰湖溃决诱因筛选中无需考虑雪崩因子。