The Two Main Mechanisms of Glacier Lake Outburst Flood in Tibet,China

With the global warming,the disasters of Glacier Lake Outburst Flood(GLOF) have taken place frequently in Tibet in recent years and attracted more and more attention.A systematic survey was conducted on the 19 GLOFs in Tibet to study their two main mechanisms.Investigations indicated that all the events occurred in end-moraine lakes,and the outburst occurred partially and instantly.And the breach had the shape of an arc or a trapezoid in overflow outburst and its top width was 3-5 times more than the height.The two main mechanisms of GLOFs in Tibetan end-moraine Lake were overflow and piping,and the overflow mechanism caused by iceberg collapse was dominated in most cases.A formula was proposed to calculate the critical thickness of iceberg tongue that determines the collapse.Granular analysis of the moraine materials revealed that seepage deformation is crucial in the outburst process.Finally,we conducted a case study of the Guangxiecuo Lake to show its possible process of outburst and estimated the peak discharge of the resulted flood.

Overview of an early warning system for Glacial Lake outburst flood risk mitigation in Dudh-Koshi Basin, Nepal

Natural disasters inflict severe damage on almost the entire spectrum of social and natural habitats. This ranges from housing and shelter, water, food, health, sanitation to information and communication networks, supply of power and energy,transportation infrastructure, and others. Nepal is a risk prone country for Glacial Lake Outburst Flood(GLOF). GLOFs exist as major challenges as they repeatedly cause a heavy toll of life and property. During such a disaster, major challenges are indeed the protection of life, property and vital life-supporting infrastructure. Any delay or laxity in disaster relief can escalate the magnitude of distress for the victims. Thus, rather than trying to take curative measures, it is better to minimize the impacts of GLOF. These measures subsequently help in reducing the magnitude of death and casualties due to a GLOF event. This reduction of impact is often achieved by optimizing preventive measures. For applying necessary deterrent measures, it is essential to disseminate information about the danger beforehand. Early Warning System(EWS) is an important step for such information dissemination for GLOF disaster management and helps to anticipate the risk of disaster and disseminate information to lives at risk. It is impossible and impractical to reduce all GLOF risks, but it is possible to reduce several impacts of a GLOF through the implementation of the EWS. This paper presents the design and implementation of an EWS for monitoring potential outbursts of a glacier lake in the Dudh-Koshi Basin, Nepal.

A framework of numerical simulation on moraine-dammed glacial lake outburst floods

Glacial outburst floods（GLOFs） in alpine regions tend to be relatively complicated, multi-stage catastrophes, capable of causing significant geomorphologic changes in channel surroundings and posing severe threats to infrastructure and the safety and livelihoods of human communities. GLOF disasters have been observed and potential hazards can be foreseen due to the newly formed glacial lakes or the expansion of existing ones in the Poiqu River Basin in Tibet, China. Here we presented a synthesis of GLOF-related studies including triggering mechanism（s）, dam breach modeling, and flood routing simulation that have been employed to reconstruct or forecast GLOF hydrographs. We provided a framework for probability-based GLOFs simulation and hazard mapping in the Poiqu River Basin according to available knowledge. We also discussed the uncertainties and challenges in the model chains, which may form the basis for further research.

Influence of inflow discharge and bed erodibility on outburst flood of landslide dam

Accurate prediction of the hydrographs of outburst floods induced by landslide dam overtopping failure is necessary for hazard prevention and mitigation. In this study, flume model tests on the breaching of landslide dams were conducted. Unconsolidated soil materials with wide grain size distributions were used to construct the dam. The effects of different upstream inflow discharges and downstream bed soil erosion on the outburst peak discharge were investigated. Experimental results reveal that the whole hydrodynamic process of landslide dam breaching can be divided into three stages as defined by clear inflection points and peak discharges. The larger the inflow discharge, the shorter the time it takes to reach the peak discharge, and the larger the outburst flood peak discharge. The scale of the outburst floods was found to be amplified by the presence of an erodible bed located downstream of the landslide dam. This amplification decreases with the increase of upstream inflow. In addition, the results show that the existence of an erodible bed increases the density of the outburst flow, increasing its probability of transforming from a sediment flow to a debris flow.

Modelling Chorabari Lake outburst flood, Kedarnath, India

In this study, the Glacier Lake Outburst Flood(GLOF) that occurred over Kedarnath in June 2013 was modeled using integrated observations from the field and Remote Sensing(RS). The lake breach parameters such as area, depth, breach, and height have been estimated from the field observations and Remote Sensing(RS) data. A number of modelling approaches, including Snow Melt Runoff Model(SRM), Modified Single Flow model(MSF), Watershed Management System(WMS), Simplified Dam Breach Model(SMPDBK) and BREACH were used to model the GLOF. Estimations from SRM produced a runoff of about 22.7 m3 during 16–17, June 2013 over Chorabari Lake. Bathymetry data reported that the lake got filled to its maximum capacity(3822.7 m3) due to excess discharge. Hydrograph obtained from the BREACH model revealed a peak discharge of about 1699 m3/s during an intense water flow episode that lasted for 10–15 minutes on 17 th June 2013. Excess discharge from heavy rainfall and snowmelt into the lake increased its hydrostatic pressure and the lake breached cataclysmically.

Glacial Lake Outburst Flood Disasters and Integrated Risk Management in China

High-risk areas for glacial lake outburst flood(GLOF) disasters in China are mainly concentrated in the middle-eastern Himalayas and Nyainqe?ntanglha(Nyenchen Tanglha Mountains), Tibetan Plateau. In the past 20 years, glaciers in these regions have retreated and thinned rapidly as a response to regional climate warming,leading to the formation of new glacial lakes and the expansion of existing glacial lakes. These areas are located in the border belt between the Indian and the Eurasian plates, where tectonic seismic activity is also frequent and intense. Earthquakes have often compromised the stability of mountain slopes, glaciers, and moraine dams, resulting in an imbalance in the state of glacial lakes and an increase of loose materials in valleys. It is foreseeable that the possibility of GLOFs and disaster occurrence will be great in the context of frequent earthquakes and continued climate warming. This article presents the temporal and spatial characteristics of GLOF disasters, as well as the conditions and mechanisms of GLOF disaster formation,and proposes an integrated risk management strategy to cope with GLOF disasters. It aims to facilitate the mitigation of the impacts of GLOF disasters on mountain economic and social systems, and improve disaster risk analysis, as well as the capability of risk management and disaster prevention and reduction.

Multiple evidences indicate no relationship between prehistoric disasters in Lajia site and outburst flood in upper Yellow River valley, China

All around the world, ancient legends exist about the Great Flood, and the influence of the Great Flood in human evolutionary history is a hotly debated topic. In China, the legend of the prehistoric Great Flood and Yu the Great's flood control has a long history and is considered to be closely linked to the establishment of the Xia Dynasty. However, there is a lack of solid scientific evidence. Against this issue, some scholars have proposed that an earthquake around 1920 BCE in the Guanting Basin along the upper reaches of the Yellow River led to the creation of a lake by damming in the Jishi Gorge and that the outburst of water from that lake led to the massive flood in the Yellow River region. These studies provided new scientific evidence for the Chinese legend. In this paper, we date skeletal samples embedded in earthquake sand blasting from the Lajia site, analyze remains from natural disasters(such as earthquakes and floods) and also archaeological remains. In addition, we compared the skeletal samples dating with that of sediments from the dammed-up lake. Our results are inconsistent with those of previous scholars. The earthquake at the Lajia site occurred no earlier than 1800 BCE, and the dammed-up lake in Jishi Gorge had disappeared by 3600 BCE. Thus, the formation and outburst of the dammed lake, the sudden death of ancient humans at the Lajia site and the ancient earthquake were independent events occurring at different times. In addition, the massive flood in the upper reaches of the Yellow River did not actually happen. Thus, we argue against and invalidate the hypothesis that the massive flood was related to Yu the Great's flood control and the establishment of the Xia Dynasty.

Flooding(or breaching)of inter-connected proglacial lakes by cascading overflow in the arid region of Western Mongolia(Mt.Tsambagarav,Mongolian Altai)

This study investigates the glacial lake outburst flood(GLOF)hazards in the Tsambagarav mountain range in Western Mongolia,focusing on the Khukhnuruu Valley and its interconnected proglacial lakes.Over the last 30 years,significant glacier retreats,driven by rising temperatures and changing precipitation patterns,have led to the formation and expansion of several proglacial lakes.Fieldwork combined with satellite data and meteorological analysis was used to assess the dynamics of glacier and lake area changes,with particular focus on the flood events of July 2021.The research reveals a substantial reduction in glacier area,particularly in the Khukhnuruu E complex,where glacier area decreased by 19.3%.The study highlights the influence of increasing temperatures and summer precipitation,which have accelerated ice melt,contributing to the expansion and eventual breaching of lakes.Additionally,lake area changes were influenced by the steepness of the terrain,with steeper slopes exacerbating peak discharge during floods.Of the studied seven lakes(Lake 1 to Lake 7),Lake 1 experienced the most dramatic reduction,with a decrease in area by 73.51%and volume by 84.84%,followed by Lake 7.This study underscores the region's vulnerability to climate-induced hazards and stresses the need for a comprehensive early warning system and disaster preparedness measures to mitigate future risks.

THE RESEARCHES OF GLACIER LAKE OUTBURST FLOODS OF THE YARKANT RIVER IN XINJIANG

The Jokulhlaup of the Yarkant River (Yarkant He) is usually csused by the sudden discharge of the glacier-dammed lake and the mode of the discharge is the rapid expansion of the subglacial channel. Keyajir (Kyagar) Glacier and Telamukanli Glacier are on the upper reaches of the Keleqin (Shaksgam) River, the chief birthplaces of this kind of flood. Up to the end of this century, since the global climate has become warmer, the glaciers have accordingly shrunk and become thinner, with the result that the size and dimensions of the glacier-dammed lakes and their outburst floods have diminished. All these simply reveal the mystery of the Jokulhlaups of the Yarkant River in Xinjiang.

Sequential Damming Induced Winter Season Flash Flood in Uttarakhand Province of India

204 persons were killed while two hydropower projects located in close proximity at Rishiganga(13.2 MW),and Tapoban(520 MW)were damaged in Dhauliganga flood of February 7,2021 in the Indian Himalaya.This incidence occurred during the winter season when the discharge of the glacier fed rivers is minimal,and no rain was experienced in the region around the time of the flood.Despite discharge of the main river,Rishiganga,not involved in the flood due to damming upstream of its confluence with Raunthi Gadhera,based on field evidences massive volume of around 6 million cu m water involved in this flood is attributed to sequential intermittent damming at three different places;(i)Raunthi Gadhera was dammed first in its upper reaches,(ii)Rishiganga river was then dammed to the north of Murunna,and(iii)finally Dhauliganga river was dammed around Rini village to the upstream of its confluence with Rishiganga river.Lacking warning system only enhanced the flood-induced devastation.Legally binding disaster risk assessment regime,together with robust warning generation,and dissemination infrastructure are therefore recommended for all major infrastructure projects.

PRELIMINARY STUDY ON FLASH FLOODS IN TARIM RIVER BASIN

Flash floods are the important events of the hydrological regime of rivers in arid areas. In the Tarim River, northwestern china, flash flood are being monitored. The observed data and investigation demonstrate the difference in time, place, fraquency and intensity of their occurrences. In this paper two main flash fled are put forward, they are rainstorm flash flood (RFF) and glacier lake outburst flood(GLOF). Two cases of flash flood in the two tributaries of the Tarim River presented in this paper. It analyses and compares the causes and the development of the two kinds of flash floods.Through further discussion about influence of flash floods on the main channel of the Tarirn River, conclusion can be drawn that the greatest flood in record of the main channel come from the GLOF of the upper reaches of the Kunmalik River, especially augmented by great ablation flood. Finally the advantages and disadvantages from flash floods to the environment of the catchment are demonstrated in the paper.

Debris Fan Produced by Failure of Canyon-Blocking Pyroclastic Flows

Ash-rich pyroclastic flows from the cataclysmic eruption of Mount Mazama (~7700 yr. B. P.), Cascade volcanic arc, Oregon, entered and blocked the narrow, bedrock-lined canyon of the Williamson River approximately 35 to 44 km from the source volcano. The blockage impounded a body of water which then released producing four stratigraphic units in the downstream debris fan. The four stratigraphic units are a boulder core comprised of locally sourced bedrock boulders and three sand-rich units including a fine-grained sand unit, a sandy pumice gravel (±basalt/hydrovolcanic tuff) unit, and a pumice pebble-bearing, crystal-rich sand unit. Hand-drilled auger holes up to ~1.6 m deep were used to obtain samples of the sand-rich units. Units were delimited using surface and down-hole observations, composition and texture, estimated density, statistical parameters of grain size, and vertical and lateral distribution of properties. Overtopping followed by rapid incision into the ash-rich pyroclastic flows progressively cleared the canyon, but a bedrock knickpoint near the head of the canyon limited the volume of debris available for transport to about 0.04 km3 to 0.08 km3. Co-deposition of bedrock boulders and lithic-rich sand was followed by rapid deposition with minimal reworking of remobilized pyroclastics. Continued draining of the impounded lake sent hyperconcentrated flows onto the debris fan depositing pumice-rich gravels that graded upward to crystal-rich sands.

昆仑山北坡冰川湖变化及其溃决风险评估

探究昆仑山北坡冰川湖时空变化及冰川湖溃决洪水(Glacier lake outburst flood,GLOF)风险评估对区域水资源安全和生态发展具有重要意义。基于Google Earth Engine(GEE)遥感计算平台分析昆仑山北坡冰川湖近30 a的变化特征和GLOF风险评估模型对当前的冰碛湖进行灾害与风险评估。结果表明:(1)1990—2023年昆仑山北坡冰川湖呈显著增长趋势,冰川湖的数量从1990年的248个增加到2023年的925个(增加了2.73倍),面积从1990年的14.99 km^(2)增加到2023年的54.83 km^(2)(增加了2.66倍),冰川湖在昆仑山北坡西部高海拔山区增加显著。(2)通过对2023年GLOF风险评估分析得出,灾害水平在叶尔羌河流域最高(约占47.2%),其次是和田河流域(约占15.7%)。风险水平较高是叶尔羌河流域(约占50.8%),叶尔羌河流域高风险冰川湖占整个昆仑山北坡高风险冰川湖的60.7%。(3)1990—2023年冰川湖的增长趋势与区域气候变化相关,山区降水增加和冰川积雪消融是冰川湖扩张的主要原因。开展冰川湖溃决洪水风险评估可为干旱区水资源可持续利用,为下游地区防灾预警提供科学依据和支撑。

“11·03”金沙江白格堰塞湖溃决洪水沉积物粒度特征

【目的】探究堰塞湖溃决洪水沉积物粒度特征和理解金沙江溃决洪水泥沙沿程变化特征。【方法】分析了“11·03”金沙江白格堰塞湖溃决洪水沉积物样品颗粒组成,计算了粒度参数,论述了泥沙特征从上到下的变化及其原因,并对比讨论了本次洪水泥沙粒度特征与其他流域洪水及古洪水沉积物泥沙粒度特征。【结果】堰塞湖溃决洪水沉积物类型为粉砂、砂质粉砂、粉砂质砂;泥沙粒径中粉砂占55.18%,砂占32.86%,黏土占11.97%。泥沙中值粒径为41.34μm,平均粒径为31.73μm,两者随离白格堰塞湖距离的增加而逐渐变小;偏度值为0.27,属正偏;峰态值为0.94,属于中等尖锐;分选系数为0.57,分选性好;泥沙的粒度分布曲线双峰占52%,主峰高而窄,峰值为100μm,次峰低而宽;单峰占48%,峰态较窄,峰值为50μm。剖面泥沙粒径组成差别很小,以砂占优,粉砂含量略小于细砂,黏土含量大多在11.0%,中值粒径值大于其平均粒径值,分选系数均小于0.6,偏度为极正偏,峰态为中等。“11·03”溃决洪水与其他洪水相比,泥沙粒度组分较细,以粉砂为主,中值粒径和平均粒径较小,峰态更宽,偏度为正偏,分选性更好。【结论】研究结果对进一步认识堰塞湖溃决洪水的泥沙特征具有重要参考价值。

基于数值模拟的大岩山崩塌-堰塞坝-溃决洪水灾害链演化过程分析

河道岸坡在地震和降雨作用下易发生崩滑,从而堵塞河道形成堰塞坝进而引发溃决洪水形成灾害链。为了清晰认识灾害链的演化过程及运动特征,以大岩山崩塌-堰塞坝-溃决洪水灾害链为研究对象,对其进行了全过程数值模拟。通过无人机航测获取了大岩山崩塌周围至下游10 km^(2)的地形数据,利用EDEM离散元数值模拟软件建立大岩山崩塌模型,反演崩塌堆积形成堰塞坝的过程;采用DB-IWHR模拟计算堰塞坝溃坝过程的流量过程线;以流量过程线作为洪水演进的上游边界条件,结合Flo-2D模拟溃决洪水的演进过程。模拟结果表明:大岩山崩塌堆积过程持续33 s,颗粒的最大崩落速度达到46.5 m/s,模拟结果的堆积范围与实际堆积范围吻合度较高;堰塞坝溃坝约1 h后流量达到最大值725 m^(3)/s;溃坝后洪水最大淹没深度为14.37 m,在溃口至下游1.5 km处的淹没深度几乎都在3 m以上,其下游淹没深度逐渐降低。河道岸坡崩滑形成灾害链的演化分析可为防灾减灾和应急救险提供理论依据。

崩塌滑坡泥石流灾害链分类研究

为了科学预防应对跨越时空的灾害链锁效应,提高多灾种灾害链风险综合防御的科学性、针对性和效能性,作者基于自己多年研究体会和国内外研究案例,开展了崩塌滑坡泥石流灾害链分类研究。崩塌滑坡泥石流灾害链是指自然因素或人类活动更多的是两者迭加作用引发的冰雪岩土崩塌滑坡或泥石流灾害作为首环而接续产生的一系列灾害链式反应,后续环节表现为碎屑流、涌浪、洪流倾泻、堰塞湖淹没、溃决洪水冲击等不同组合,具有空间关联、时间接续、动力转换、灾情放大的基本特点。根据作者经验和国内外诸多典型案例的分析综合,作者提出了崩塌滑坡泥石流为首环的灾害链的基本认识、分类依据和包括5类21种的分类体系。第1类是自然崩塌滑坡接续灾害链,包括崩塌滑坡间歇级联、周期接续、多级顺直俯冲和多级折转冲击等4种灾害链。第2类是自然崩塌滑坡泥石流及其转化灾害链,包括崩塌滑坡导致激流倾泻、涌浪传播、涌浪-堰塞-淹没-溃决、转化为泥石流、沟道堵溃-泥石流淤堵河道、泥石流-淤堵-洪水和土体液化-泥土流灾害链等7种灾害链。第3类是工程土体滑坡泥石流及其转化灾害链,包括滑坡-滑坡、泥石流-堵河洪水、滑坡-泥石流和尾矿坝溃决-泥石流等4种灾害链。第4类是雪崩冰崩滑坡泥石流及其转化灾害链,包括雪崩-埋压-堵塞-洪水泥石流、冰崩岩崩-滑坡-涌浪-堰塞-溃决和冰崩滑坡-冰湖溃决-洪水泥石流等3种灾害链。第5类是火山或海域崩塌滑坡泥石流灾害链,包括火山滑坡-泥石流-堰塞、海岸崩塌滑坡-海啸和海底滑坡-泥石流等3种灾害链。本项研究试图为研究每一种类崩塌滑坡泥石流灾害链的静力学、动力学和运动学指明方向,为建立整体论与分割论相结合的地质灾害链预防应对工程技术体系和决策支持平台奠定理论基础。

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。

堰塞湖风险处置研究现状与展望

科学认知堰塞湖基本特征、高效评估堰塞湖风险以及提升堰塞湖应急处置技术是缓和堰塞湖威胁和降低堰塞湖灾损的关键。从堰塞湖分布、成因、蓄水库容、生命周期以及堰塞湖灾害特点等方面系统分析了堰塞湖基本特征,从定性、定量以及灾害链角度系统总结了堰塞湖危险性评估方法,并结合堰塞湖溃决机理系统分析当前堰塞湖溃决应急监测困境、引流槽除险技术水平和疏通开挖机械设备现状。基于当前研究的局限性,凝炼堰塞湖应急处置研究未来应重点关注的5个问题:①堰塞体堆积形态分区机制;②强非恒定流输沙理论;③大尺度堰塞湖溃决模型试验;④堰塞湖应急处置专用机械设备研制;⑤堰塞湖溃决洪峰动态追踪。研究成果可为高风险堰塞湖风险评估、应急处置及区域防灾减灾规划提供有益参考。

贵平煤矿地质灾害研究及防治

随着煤矿开采的不断深入,所引起的地质灾害越发严重,特别是在开采多煤层时,地质灾害影响更为严重。为加强对山体滑坡、陡岩崩塌、泥石流、地面塌陷、地裂缝等地质灾害的防治,改善煤矿地质环境,根据矿井实际情况,结合各类地质灾害发生的特点,采取对采空区进行地表下沉量预测、无人机遥感监测等有效的防治措施,实现对风险的有效预防与控制,并加强地质灾害治理,保护煤矿地质生态环境,实现矿井长期安全稳定发展。

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.