近20a来西藏朋曲流域冰湖变化及潜在溃决冰湖分析

全球气候变暖,青藏高原冰川普遍处于退缩趋势,由此引发的冰湖溃决洪水的灾害也随之增加.通过对2000/2001年度卫星遥感数据解译结果和1987年国际联合考察的朋曲流域冰湖溃决洪水结果的分析,研究了近20a来朋曲流域内冰湖的变化.结果显示,该流域中的冰湖数量有减少,但冰湖的面积却在增加,这是同期全球气候变暖的结果.在提供了冰湖编目数据的基础上,识别了有潜在危险的冰湖,为冰湖溃决洪水早期预警系统提供了科学依据.     

冰湖溃决灾害风险研究进展及其展望

系统回顾了国内外冰湖溃决灾害风险研究现状,结果显示,以往冰湖溃决灾害风险评估研究过多集中于冰湖溃决致灾诱因、特征,溃决危险性评价和溃决概率预测以及溃决洪峰流量及其演进模拟研究等自然风险方面,而承灾区经济社会系统脆弱性、暴露性和适应性风险研究却较为缺乏。因此,开展冰湖溃决灾害综合风险研究,不仅对冰湖溃决危险性评价意义重大,而且对于下游承灾区防灾减灾和预警体系建立也具有重要的理论参考价值。     

2013年西藏嘉黎县“7.5”冰湖溃决洪水成因及潜在危害

冰湖溃决洪水（泥石流）是西藏自治区主要自然灾害之一. 2013年7月5日,西藏自治区嘉黎县忠玉乡发生“7.5”冰湖溃决洪水灾害事件,导致人员失踪,房屋被毁,桥梁、道路等基础设施遭到严重破坏,直接经济损失高达2.7亿元. 基于不同时间段地形图和遥感影像资料,利用地理信息技术,发现导致“7.5”洪灾的溃决冰湖为然则日阿错. 该冰湖溃决的直接诱因可能是雪崩和冰崩的共同作用,溃决前的强降水过程及气温的快速上升是其间接原因,而冰湖长期稳定的扩张导致水量聚集是其溃决并造成巨大灾害的基础. 然则日阿错溃决后形成2个冰湖,面积分别为0.25 km²和0.01 km²,再次发生溃决的概率极小. 这次溃决洪水和泥石流灾害事件阻塞了尼都藏布的罗琼沟及衣布沟,并形成2处面积分别为0.33 km²和0.13 km²堰塞湖,且存在溃决风险,在今后一段时间内应加强监测工作与排险工程实施.     

Glacial lakes and glacial lake outburst flood in a Himalayan basin using remote sensing and GIS

Glacial hazards relate to hazards associated with glaciers and glacial lakes in high mountain areas and their impacts downstream. The climatic change/variability in recent decades has made considerable impacts on the glacier life cycle in the Himalayan region. As a result, many big glaciers melted, forming a large number of glacial lakes. Due to an increase in the rate at which ice and snow melted, the accumulation of water in these lakes started increasing. Sudden discharge of large volumes of water with debris from these lakes potentially causes glacial lake outburst floods (GLOFs) in valleys downstream. Outbursts from glacier lakes have repeatedly caused the loss of human lives as well as severe damage to local infrastructure. Monitoring of the glacial lakes and extent of GLOF impact along the downstream can be made quickly and precisely using remote sensing technique. A number of hydroelectric projects in India are being planned in the Himalayan regions. It has become necessary for the project planners and designers to account for the GLOF also along with the design flood for deciding the spillway capacity of projects. The present study deals with the estimation of GLOF for a river basin located in the Garwhal Himalaya, India. IRS LISSIII data of the years 2004, 2006 and 2008 have been used for glacial lake mapping, and a total of 91 lakes have been found in the year 2008, and out of these, 45 lakes are having area more than 0.01?km². All the lakes have been investigated for vulnerability for potential bursting, and it was found that no lake is vulnerable from GLOF point of view. The area of biggest lake is 0.193, 0.199 and 0.203?km² in the years 2004, 2006 and 2008, respectively. Although no lake is potentially hazardous, GLOF study has been carried out for the biggest lake using MIKE 11 software. A flood of 100-year return period has been considered in addition to GLOF. The flood peak at catchment outlet comes out to be 993.74, 1,184.0 and 1,295.58 cumec due to GLOF; 3,274.74, 3,465.0 and 3,576.58 cumec due to GLOF; and 100-year return flood together considering breach width of 40, 60 and 80?m, respectively.     

亚洲高山区冰湖溃决洪水事件回顾

冰湖溃决洪水是由冰湖快速大量释水所导致的自然灾害。在全球变暖背景下,亟待建立完整的冰湖溃决洪水数据库,以进一步对冰湖进行危险性评估和风险管理。整理了亚洲高山区（青藏高原及周边地区）的冰湖溃决洪水资料,得出冰湖溃决洪水主要分布在天山山脉、喀喇昆仑山、喜马拉雅山脉、念青唐古拉山、横断山等区域。20世纪以来,亚洲高山区共计发生冰湖溃决洪水277起,其中冰碛湖溃决洪水113起,冰坝湖溃决洪水164起。导致冰碛湖溃决的诱因以冰-雪崩或冰川滑塌为主导,占50.1%,埋藏冰融化或管涌、强降水或上游来水、滑坡-岩崩以及地震占比分别为23.1%、18.5%、7.4%和0.9%。1980年以来,冰碛湖溃决洪水的发生频率呈较弱的增长趋势;但由于发生溃决的冰湖趋于小型化,其溃决水量与洪峰流量在喜马拉雅山脉、天山山脉等地区呈显著下降趋势。2010—2018年间喜马拉雅山脉中段发生8起冰湖溃决洪水事件,远高于天山山脉、喜马拉雅山脉东段和念青唐古拉山等地区,成为新的高发区,是未来重点关注的地区。在未来冰湖溃决洪水频率可能增加的状况下,相关国家和地区在应对冰川灾害、实现区域防灾减灾等方面需要加强沟通交流,共同建立跨区域协调的防灾体系。     

冰湖溃决泥石流的形成、演化与减灾对策

本文分析了主要由冰滑坡和冰崩入湖导致的冰湖溃决的机理和条件.进而,从气候条件、水文条件、终碛堤、冰湖规模、冰滑坡、沟床特征和固体物质补给等方面分析了冰湖溃决泥石流的形成条件和特点,归纳出冰湖溃决泥石流沿程演化的6种模式:溃决洪水-稀性泥石流、溃决洪水-黏性泥石流、溃决洪水-稀性泥石流-黏性泥石流、溃决洪水-黏性泥石流-稀性泥石流、溃决洪水-稀性泥石流-黏性泥石流-稀性泥石流和溃决洪水-黏性泥石流-稀性泥石流-洪水.针对冰湖溃决泥石流突发性强、频度低、洪峰高、流量大、流量过程暴涨暴落、破坏力强和灾害波及范围广等特点,提出了7点减灾对策.     

希夏邦马峰东坡冰川与冰川湖泊变化遥感监测

1977-2003年的遥感影像显示,希夏邦马峰东坡的冰川在迅速退缩,而其相应的冰川湖泊在迅速增大.南部的吉葱普冰川每年的退缩速度57099 m²,冰舌退缩48 m·a^-1,相应的卢姆池米冰湖面积增加速度大约为79048 m²·a^-1;北面的热强冰川退缩速度在63224 m²·a^-1,冰舌退缩71 m·a^-1,相应的扛西错冰湖面积增加约73 425 m²·a^-1.从这两个冰湖的类型和变化分析,认为其具有发生冰川湖泊溃决洪水的潜在危险.     

Monitoring cryosphere and associated flood hazards in high mountain ranges of Pakistan using remote sensing technique

Knowledge of Himalayan cryosphere seems to be an outstanding requirement for assessment of glacier storage, water balance analysis, planning of water resources and flood hazard monitoring. A stepwise approach through mapping glaciers and glacial lakes using satellite remote sensing data and investigating potential glacial lake outburst flood (GLOF) hazards was adopted for the three Hindukush, Karakoram and Himalayan (HKH) ranges of Pakistan. The findings of the study revealed 5,218 glaciers in the cryosphere of HKH ranges. The cumulative glacial cover of over 15,000 km² contains ice reserves of about 2,738 km³. About 46 % of the Karakoram glaciers are contributing 77 % to the total glacial cover and 87 % to the cumulative ice reserves of the country. The 33 % Himalayan glaciers and 21 % Hindukush glaciers contribute only 3 and 10 % ice reserves, respectively. Among 2,420 glacial lakes identified in the three HKH ranges, 52 were classified as critical lakes that can pose GLOF hazard for the downstream communities. Most of the potential hazardous lakes lie in the Karakoram and Himalayan ranges, the monitoring of which is crucial to reduce high risk of future floods hazard in this fragile mountain ecosystem of the Himalayan region.     

青藏高原东南部来古冰湖变化及其溃决洪水评估

冰湖溃决洪水(Glacial lake outburst flood,简称GLOF)灾害是冰川区最常见、危害最大的灾害类型之一,历来是国内外学者研究的关键科学问题。在全球变暖的大背景下,冰川退缩加剧,其下游冰湖扩张快速,湖面升高,溃决风险提高。青藏高原尤其是东南部地区孕育着大量的冰湖,在过去的几十年间,冰湖溃决洪水威胁着当地人民的生产生活。基于LANDSAT遥感影像,本文获取了青藏高原东南部雅弄冰川和来古冰湖1986年、1990年、1994年、1997年、2000年、2003年、2005年、2011年、2013年和2017年共10期湖面面积,并结合实地测量的冰湖水深资料,计算了冰湖对应年份的储水量,建立冰湖面积与储水量变化序列;结合野外调查从冰湖面积与水量变化趋势和突发事件两方面探讨冰湖溃决可能性;利用BREACH模型和SMPDBK模型估算和模拟来古冰湖溃决洪水,做灾害预警分析。结果表明,1986~2017年冰湖上湖变化不大,而来谷下湖处于持续扩张中,面积由1986年的1.151±0.070 km^2扩张至2017年的3.148±0.097 km^2,水量由0.645×10^8 m^3增加至2.143×10^8 m^3,雅弄冰川在1986~2013年持续后退,在2013~2017年突然前进;经讨论其溃决风险得出冰川滑动入湖导致湖水瞬时涌出从而造成溃坝的可能性较高;利用BREACH模型及SMPDBK模型对来古冰湖溃决洪水模拟结果表明,当来古下湖湖水受冰体挤压抬升发生溃决时,溃决洪水将严重威胁然乌镇及其上游居民的生命和财物安全。     

Glacial hazards in the Rolwaling valley of Nepal and numerical approach to predict potential outburst flood from glacial lake

In recent years, climate change and retreating glaciers constitute a major hazard in the Himalaya of South Asia. Glacial lakes are rapidly developing or increasing due to climate change. The rapid development of the lake may cause outburst of the lake. The outburst discharge from the glacial lake can cause catastrophic flooding and disaster in downstream area. Therefore, it is necessary to investigate the impact of climate change on glacial lakes and to understand the characteristics of the glacial lake outburst. In this study, the field assessment of Tsho Rolpa Glacial Lake in the Himalaya of Nepal has been presented and the impact of climate change on this glacial lake has been discussed. The Tsho Rolpa Glacial Lake is the largest and most potentially dangerous glacial lake in Nepal. In addition, a numerical model has been also developed for computing the characteristics of glacial lake outburst due to moraine dam failure by seepage and water overtopping. The numerical model is tested for the flume experimental cases. The simulated results of the outburst discharge, the dam surface erosion, and the temporal variation of the moisture movement in the dam are compared with those obtained from the hydraulic model experiments. The moisture profile calculated by numerical model was agreeable with the experimental moisture profile. The simulated failure surface of the dam due to seepage by considering the suction in slope stability analysis gave more agreeable results than the Janbu's simplified method. The results of the outburst discharge and dam surface erosion also agreed with the experimental results.     

Debris flows triggered from non-stationary glacier lake outbursts: the case of the Teztor Lake complex (Northern Tian Shan,Kyrgyzstan)

One of the most far-reaching glacier-related hazards in the Tian Shan Mountains of Kyrgyzstan is glacial lake outburst floods (GLOFs) and related debris flows. An improved understanding of the formation and evolution of glacial lakes and debris flow susceptibility is therefore essential to assess and mitigate potential hazards and risks. Non-stationary glacier lakes may fill periodically and quickly; the potential for them to outburst increases as water volume may change dramatically over very short periods of time. After the outburst or drainage of a lake, the entire process may start again, and thus these non-stationary lakes are of particular importance in the region. In this work, the Teztor lake complex, located in Northern Kyrgyzstan, was selected for the analysis of outburst mechanisms of non-stationary glacial lakes, their formation, as well as the triggering of flows and development of debris flows and floods downstream of the lakes. The different Teztor lakes are filled with water periodically, and according to field observations, they tend to outburst every 9–10 years on average. The most important event in the area dates back to 1953, and another important event occurred on July 31, 2012. Other smaller outbursts have been recorded as well. Our study shows that the recent GLOF in 2012 was caused by a combination of intense precipitation during the days preceding the event and a rapid rise in air temperatures. Analyses of features in the entrainment and depositional zones point to a total debris flow volume of about 200,000 m³, with discharge ranging from 145 to 340 m³ s^?1 and flow velocities between 5 and 7 m s^?1. Results of this study are key for a better design of sound river corridor planning and for the assessment and mitigation of potential GLOF hazards and risks in the region.     

Estimating the contribution of glacial meltwater to Ranwu Lake,a proglacial lake in SE Tibet,using observation data and stable isotopic analyses

It is important for both current monitoring and paleoenvironmental research conducted on proglacial lakes and their adjacent glaciers to clarify the hydrological processes operating on these lakes. However, in remote regions with limited accessibility it may be difficult to study hydrological processes by direct monitoring. In this study, we use measurements of stable isotopic compositions to trace the multiple water sources contributing to Ranwu Lake, a proglacial lake in south-eastern Tibet. Using stable isotopic data from precipitation, inflowing rivers and the lake water, a water and isotope mass balance modelling method was used to calculate the ratio of evaporation to input. Subsequently, using hydrological and climatic data for the outflow, the largest inflow and precipitation, other hydrological elements of the lake water balance were also calculated. The results demonstrate that the ratio of evaporation to inflow is as low as 0.009, the lowest value observed for the Tibetan Plateau, indicating that Ranwu Lake is a through-flow lake with a very short retention time. Glacial meltwater accounts for at least 55% of total runoff, the highest value observed for the Tibetan Plateau, indicating that the sediments of Ranwu Lake may have considerable potential for reconstructing variations in the activity of the local glaciers. Finally, we note that it may be inappropriate in this glacier-fed lake to use the intersection of the local meteoric water line with the lake water line for determining the isotopic composition of the input water, and this possibility must be carefully considered when stable isotope mass modelling is used in proglacial lakes.     

基于Fluent数值模拟的冰湖涌浪分析 ——以西藏聂拉木县嘉龙错为例

冰湖溃决洪水或泥石流（GLOF）是青藏高原主要灾害之一,其形成的灾害链对人民的生命财产安全造成了严重的威胁,其中冰崩导致的冰湖溃决是GLOF的主要灾害形式,但由于其发生位置偏远、间隔时间长、随机性强,导致实地观测资料缺乏,冰崩入湖形成的涌浪机理和过程仍不清晰,而涌浪的规模是GLOF造成下游灾害大小的最主要因素。为分析冰湖涌浪的产生、沿程传播过程和对冰碛坝的爬坡高度,以西藏聂拉木县嘉龙错为例,采用有限体积法,基于流体计算软件Fluent,模拟了嘉龙错补给冰川发生冰崩导致冰湖涌浪的过程。结果表明：数值模拟能较好地对涌浪的产生、规模、沿程传播和对岸爬坡过程进行再现,涌浪初始高度随着冰湖水深、冰体入湖速度和冰体厚度的增加而增大,涌浪高度增加趋势随着冰体入湖速度和冰湖水深的增加而增大,随着冰体厚度的增加而减小。     

冰碛湖溃决易发性的定量评价

世界范围内的冰碛湖溃决往往造成巨大经济损失和人员伤亡.通过分析不含死冰的冰碛坝溃决机理和相关影响因素,采用控制变量法,以喜马拉雅山区21个溃决冰碛湖及其周围未溃决冰碛湖为研究对象,采用6个无量纲影响因子可以合理评估喜马拉雅山区和加拿大哥伦比亚省西南地区以及美国西北部地区的冰湖溃决易发性,但喜马拉雅山区不同级别判别阈值较加拿大哥伦比亚省西南地区偏大.危险冰体坡度因子、危险冰体温度因子、冰川坡向因子、危险冰体与冰碛湖体积因子、危险冰体与冰湖的运动因子、冰碛坝坡度因子是影响不含死冰冰碛湖溃决的主要因子,由这些影响因子构成的冰碛湖溃决易发性定量评价方法,可以用于其他地区的冰碛湖溃决易发性评价.      

Palaeogeographic reconstruction of proglacial lakes in Estonia

This paper describes a Geographical Information System (GIS)-based palaeogeographic reconstruction of the development of proglacial lakes formed during deglaciation in Estonia, and examines their common features and relations with the Baltic Ice Lake. Ice marginal positions, interpolated proglacial lake water levels and a digital terrain model were used to reconstruct the spatial distribution and bathymetry of the proglacial lakes. Our results suggest that the proglacial lakes formed a bay of the Baltic Ice Lake after the halt at the Pandivere-Neva ice margin about 13.3 cal. kyr BP. Shoreline reconstruction suggests that two major proglacial lake systems, one in eastern and the other in western Estonia, were connected via a strait and thus had identical water levels. The water budget calculations show that the strait was able to transfer a water volume several times greater than the melting glacier could produce. As this strait compensated for the water level difference between the two lake parts, the subsequent further merging in north Estonia did not result in catastrophic drainage, as has been proposed.     

入湖冰川物质平衡序列重建与分析--以喜马拉雅山北坡龙巴萨巴冰川为例北大核心CSCD

入湖冰川受冰湖作用影响,物质损失速率高于其他类型冰川,并导致冰湖进一步扩张,冰湖溃决风险增加。建立入湖冰川物质变化序列,对揭示不同类型冰川对气候变化的响应特征,以及评估冰湖溃决风险研究具有重要意义。基于中国地面气象要素驱动数据集和实测气象数据,采用冰川表面能量-物质平衡模型估算了冰川表面物质变化,并结合冰川流动和末端退缩特征,重建了1989-2018年龙巴萨巴冰川物质变化序列。结果表明,近30a龙巴萨巴冰川总物质损失为0.315km^(3)w.e.,平均物质变化速率为-0.114km^(3)w.e.·a^(-1)。冰川平均表面物质平衡为-0.26m w.e.·a^(-1),表面消融是冰川物质亏损的主要贡献因素。气温变化对冰川表面物质损失的影响高于降水;冰川表面物质平衡对夏季气温和降水变化的敏感性强于其他季节;表碛覆盖加速了冰川表面消融,且较薄的表碛厚度会加剧冰川表面物质损失。     

我国西藏地区冰湖溃决灾害综述

冰湖溃决是我国西藏地区典型的地质灾害类型之一,具有突发性强、规模大、破坏力强和危害范围广等特点,往往造成下游地区遭受惨重的生命财产损失。冰湖溃决成因特征是形成机制、早期识别和危险性评价等冰湖溃决研究的基础,受客观条件限制,我国西藏冰湖溃决的基础调查工作存在资料分散甚至缺失的局限性。为解决这个难题,通过资料收集、遥感解译和野外调查等技术手段,重新梳理了我国西藏地区的冰湖溃决事件及基本特征,共调查出33个冰湖37次溃决事件,其中2个为冰川阻塞湖（简称冰川湖）,划定了冰湖溃决高发地带的地理分布位置,分析出冰崩/冰滑坡、埋藏冰融化、冰川融水、强降水、泥石流和上游冰湖溃决洪水6种诱发原因,为我国西藏冰湖溃决研究提供基础调查成果和参考依据。     

Cryospheric hazards and risk perceptions in the Sagarmatha (Mt. Everest) National Park and Buffer Zone,Nepal

Glacial lake outburst floods (GLOFs) are among the most serious cryospheric hazards for mountain communities. Multiple studies have predicted the potential risks posed by rapidly expanding glacial lakes in the Sagarmatha (Mt. Everest) National Park and Buffer Zone of Nepal. People’s perceptions of such cryospheric hazards can influence their actions, beliefs, and responses to those hazards and associated risks. This study provides a systematic approach that combines household survey data with ethnography to analyze people’s perceptions of GLOF risks and the socioeconomic and cultural factors influencing their perceptions. A statistical logit model of household data showed a significant positive correlation between the perceptions of GLOF risks and livelihood sources, mainly tourism. Risk perceptions are also influenced by spatial proximity to glacial lakes and whether a village is in potential flood zones. The 2016 emergency remediation work implemented in the Imja Tsho (glacial lake) has served as a cognitive fix, especially in the low-lying settlements. Much of uncertainty and confusions related GLOF risks among locals can be attributed to a disconnect between how scientific information is communicated to the local communities and how government climate change policies have been limited to awareness campaigns and emergency remediation efforts. A sustainable partnership of scientists, policymakers, and local communities is urgently needed to build a science-driven, community-based initiative that focuses not just in addressing a single GLOF threat but develops on a comprehensive cryospheric risk management plan and considers opportunities and challenges of tourism in the local climate adaptation policies.

     

A geospatial analysis of Samudra Tapu and Gepang Gath glacial lakes in the Chandra Basin,Western Himalaya

Geospatial studies carried out in two major proglacial lakes of Samudra Tapu and Gepang Gath (Chandra Basin, Western Himalaya) showed substantial expansion in their area and volume over the last four decades (1971–2014). The linear and areal expansions for the lakes Samudra Tapu and Gepang Gath were 1889, 1509 m and 1, 0.6 km², respectively. The results show that increased melting of the feeder glaciers over this period is major contributor to expand the volumes approximately 20 times of both the lakes Samudra Tapu and Gepang Gath. This expansion of lakes volume of Samudra Tapu and Gepang Gath from 3.4 × 10⁶ to 67.7 × 10⁶ and 1.5 × 10⁶ to 27.5 × 10⁶ m³, respectively, is quite significance in terms of hazards generated from glacial lake outburst floods (GLOF). This kind of climate change induced increase in the rate of glacial melting is a cause of concern, as the Himalaya Mountains may turn out to be vulnerable to natural hazards like GLOF.     

Threat of glacial lake outburst flood to Tehsil Gupis from Khukush Lake, District Ghizer, Gilgit Baltistan, Pakistan

Glacial lake outburst flood (GLOF) is a powerful natural phenomenon that is very active in the Karakoram and Himalayas. This paper presents a case study from Gupis Tehsil in northern areas of Pakistan that is exposed to GLOFs from nine different glacial lakes in its upper catchment areas. Khukush Lake being the largest of all the glacial lakes has been studied and a flood attenuation model has been created for the whole Gupis Tehsil. This lake covers almost 2.2 km² of surface area, and its calculated volume is 2.6 × 10⁴ m³. In case of its outburst, the peak flow discharge is calculated to be 7,642 m³/s. The catchment area which contributes water and debris to the lake is 170 km². This lake is dammed by a glacial moraine, which is not strong enough to sustain the pressure for a longer period of time. Other factors that are reducing the reliability of the dam are the secondary hazards which are in direct contact with the lake, and in case of their reactivation, they can put severe impacts on the dam. There are eight potential sites of the snow avalanche activity where debris along with snow may fall directly into the lake producing a strong wave. This strong wave of water will increase the pressure on the dam and ultimately will increase the probability for its outburst. The presense of water springs towards the downstream side of the natural dam also indicate the presence of hidden channels passing through the dam which may weaken the shear strength of the dam. Almost 24 villages settled along either sides of the Gupis River are critically studied for the expected flood from Khukush Lake. With few exceptions, almost 20–25 % area of all the villages will be affected from this flood.