Flow hydraulics and geomorphic effects of glacial‐lake outburst floods in the Mount Everest region,Nepal     

Daniel A. Cenderelli  Ellen E. Wohl 《地球表面变化过程与地形》2003,28(4):385-407

Glacial‐lake outburst floods (GLOFs) on 3 September 1977 and 4 August 1985 dramatically modified channels and valleys in the Mount Everest region of Nepal by eroding, transporting, and depositing large quantities of sediment for tens of kilometres along the flood routes. The GLOF discharges were 7 to 60 times greater than normal floods derived from snowmelt runoff, glacier meltwater, and monsoonal precipitation (referred to as seasonal high flow floods, SHFFs). Specific stream power values ranged from as low as 1900 W m^?2 in wide, low‐gradient valley segments to as high as 51 700 W m^?2 in narrow, high‐gradient valley segments bounded by bedrock. Along the upper 16 km of the GLOF routes, the reach‐averaged specific stream power of the GLOFs was 3·2 to 8·0 times greater than the reach‐averaged specific stream power of the SHFFs. The greatest geomorphic change occurred along the upper 10 to 16 km of the GLOF routes, where the ratio between the GLOF specific stream power and the SHFF specific stream power was the greatest, there was an abundant supply of sediment, and channel/valley boundaries consisted primarily of unconsolidated sediment. Below 11 to 16 km from the source area, the geomorphic effects of the GLOFs were reduced because of the lower specific stream power ratio between the GLOFs and SHFFs, more resistant bedrock flow boundaries, reduced sediment supply, and the occurrence of past GLOFs. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

黄河下游非恒定输沙数学模型——Ⅱ模型验证   总被引：9，自引：1，他引：9       下载免费PDF全文

张红武  黄远东  赵连军  江恩惠 《水科学进展》2002,13(3):271-277

利用所构建的非恒定输沙数学模型,对黄河下游铁谢至孙口河段内的1977年高含沙洪水、1982年大水少沙型洪水以及1996年典型洪水进行了数值模拟.模拟结果证明了数学模型的可靠性,表明该模型不仅能模拟黄河下游河道一般洪水和高含沙洪水的水沙传播、水位变化及河床变形等,而且对模拟现行严重萎缩河道内的洪水演进及河床冲淤特性也有较好的适应性.  相似文献   

1998年长江流域洪水与海温异常关系的数值模拟研究   总被引：5，自引：0，他引：5  

Guo Yufu  Zhao Yan  Wang Jia 《大气科学进展》2002,19(3):391-404

用IAP／LASG GOALS模式对1998年长江流域洪水与太平洋和印度洋海表温度异常之间的关系进行了数值模拟研究。利用观测的全年海表温度，模式能再现1998年夏季长江流域的暴雨，模式也能再现观测的1998年夏季西太平洋副高异常的基本特征。设计了一系列不同海区和不同时段的海温异常的敏感性试验。试验结果表明：印度洋海温异常是造成1998年长江流域洪水的主要因子；印度洋和西太平洋海温异常与西太副高的异常有更紧密的关系；夏季海表温度异常对1998年长江流域暴雨和西太副高异常的作用与冬春海温异常的作用相比要大得多。  相似文献   

郁江南宁17场洪水之合成面雨量特征分析     

吴兴国  苏荣在 《气象研究与应用》2002,23(2):3-5

对郁江南宁 17场洪水的合成面雨量分布特征作了较系统的分析 ,发现引发南宁洪水的主要天气系统及其配置、合成面雨量的流域值及“6 8.8”大洪水和“0 1.7”特大洪水的合成面雨量表征 ,对今后进一步做好重大洪水的气象服务具有十分积极的意义  相似文献   

Example of a debris-flow risk analysis from Vancouver Island,British Columbia,Canada     

Ron Arksey  Doug VanDine 《Landslides》2008,5(1):121-126

In July 2005, a debris flow and a water flood occurred on two adjacent gullies in the White River area, on northern Vancouver Island in British Columbia, Canada. The 16,000 m³ debris flow buried approximately 7.5 ha of second-growth trees, buried approximately 500 m of a forestry road, and reached two fish-bearing streams. The water flood eroded approximately 240 m of the same forestry road and plugged four culverts before overtopping and inundating the road. To better plan for future events, risk analyses of debris flows, debris floods, and water floods were carried out for the two gullies involved, plus a third adjacent gully. The elements at risk that were analyzed included, in order of priority: users of the forestry road, the fish-bearing streams, the forestry road itself, and a timber bridge. Using a series of qualitative, but defined, relative-risk matrices, the following components of specific risk were estimated for each of the three types of events on each of the three gullies for each of the four elements at risk: probability of occurrence, probability that the event will reach or otherwise affect the site of the element at risk, the probability that the element at risk will be at the site when the event occurs, and the probability of loss or damage resulting from the element being at the site when the event occurs.  相似文献   

1855年黄河大改道与百年灾害链     

王涌泉 《地学前缘》2007,14(6):6-10

1855年黄河铜瓦厢决口北流,改道从山东入海,是一次百年灾害链形成的巨变,黄淮海平原成为中国水灾的中心。经研究发现:1740—1818年为中国地震宁静期,黄河流域正处于干旱枯水期;1819年印度卡其发生8.3级大地震,黄河出现多泥沙特大洪水,河南兰阳以下近30 km河道严重淤塞;1819—1879年大地震密集出现,并有9级以上特大地震4次,其中1833—1870年大地震主要分布在东亚;黄河因而于1841—1843年连续出现特大洪水,造成下游多次决溢、以致改道。文中第一次以科学和历史结合给出解释,其结论可供当前地球科学灾害链研究及治黄参考。  相似文献   

Physical‐scale modelling of jökulhlaups (glacial outburst floods) with contrasting hydrograph shapes     

E. Lucy Rushmer 《地球表面变化过程与地形》2007,32(6):954-963

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Influence of glacial retreat on natural hazards of the Palcacocha Lake area, Peru   总被引：1，自引：1，他引：0  

Vít Vilímek  Marco Luyo Zapata  Jan Klimeš  Zdeněk Patzelt  Nelson Santillán 《Landslides》2005,2(2):107-115

In this article we describe natural hazards associated with outburst floods of Palcacocha Lake and landslide events on the slopes of its moraine dam, in Cojup Valley, Cordillera Blanca (Peru). These events occurred in the last 70 years and some of them resulted in disasters, which strongly affected the city of Huarás. Field investigations and reference expression hydrodynamic tests as well as archive satellite images and aerial pictures were used to describe the evolution of hazards connected with Palcacocha Lake. Expression hydrodynamic tests proved a high permeability of sandy gravels glacial sediments, which form the present-day lake dam. Seepage through the natural dam forming small ponds below the overflow spillways occurs. A retreat of the glacial tongue causing an increase of the lake volume and unloading of the slope toe areas are the most important recent processes that influence the potential hazards affecting the Cojup valley. The research has proved that the climate warming and ongoing deglaciation play a very significant role in the change of natural hazards conditions in high mountains.  相似文献   

A comparison of the flood precipitation episode in August 2002 with historic extreme precipitation events on the Czech territory     

Daniela &#x;ez ov  Marek Ka&#x;par  Miloslav Müller  Zbynk Sokol  Vilibald Kakos  David Hanslian  Petr Pe&#x;ice 《Atmospheric Research》2005,77(1-4):354

The hydro-meteorological characteristics of the flood from August 2002, which affected a great part of the Czech territory, particularly the Vltava and Labe river basin, were compared with corresponding conditions during similar flood events in the summer seasons of 1997, 1890, 1897 and 1903. The comparison shows analogies in synoptic conditions and causal precipitation heights. The heaviest precipitation fell in the area of a considerable horizontal pressure gradient on the rearward side of the cyclone which advanced very slowly to the north-east across Central Europe and created conditions for the transport of moist air as well as for an organized long-term updraft enhanced in orographically exposed regions. The varying features of the individual events were based on the spatial–temporal distribution of causal precipitation and also on the very different saturation of the catchments. It was chiefly the extraordinary time concentration of precipitation together with the highest catchment saturation that made the flood in 2002 the most extreme.The extremeness of meteorological fields during two episodes in July 1997 was compared with two episodes in August 2002 with the aid of the reanalysis data from ECMWF. The first episode in 1997 and the second episode in 2002 were the most similar and more extreme in terms of the large-scale fields of basic meteorological quantities. The similar features of these episodes are specifically an intensive influx of moisture into Central Europe and intensive upward motions in the precipitation area. The extremeness of upper- and low-level potential vorticity fields was evaluated to diagnose the behavior of the cyclone and frontal precipitation bands accompanying it. The suitable spatial configuration of positive upper- and low-level potential vorticity anomalies induced an additional amplification of upward motions in the precipitation area that apparently contributed to triggering the heavy precipitation over Central Europe. On the whole, quantities reached more extreme values during the second episode in 2002.  相似文献   

MELTWATER FEATURES THAT SUGGEST MIOCENE ICE-SHEET OVERRIDING OF THE TRANSANTARCTIC MOUNTAINS IN VICTORIA LAND, ANTARCTICA   总被引：2，自引：0，他引：2  

GEORGE H. DENTON  DAVID E. SUGDEN 《Geografiska Annaler: Series A, Physical Geography》2005,87(1):67-85

ABSTRACT. We illustrate here spectacular meltwater features associated with outburst floods beneath an ice sheet that overrode the Transantarctic Mountains in southern Victoria Land. Because of long-term hyperarid polar climate, these features are part of an ancient landscape preserved for about 14 million years. Some channels are associated with areal scouring of basement rocks extending from sea level to as much as 1200–2100 m elevation in coastal regions. Scablands with scallops, potholes and plunge pools are cut in Beacon Super group sandstones and Ferrar Dolerite and cover wide areas of high western plateaus near the mountain crest. Subglacial channel systems commonly originate near divides and converge downhill toward the northeast. We argue that the landforms were created beneath a major Antarctic Ice Sheet that submerged the whole area, with the possible exception of the high peaks of the Royal Society Range, as it flowed northeastward toward the outer Antarctic continental shelf. Areal scouring, associated with warm-based regimes, is restricted to the lower slopes close to the coast. In the higher terra in, meltwater channels and scabland alongside preserved patches of regolith are best explained by the breaching of cold-based ice on the mountain rim by subglacial melt water outbursts. Melt from warm-based ice, along with subglacial lakes trapped upstream of the mountain rim, are possible sources of the meltwater necessary to form the channel systems and scablands.  相似文献