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Detecting the Legacy of Catastrophic Lake Outbursts in the Nepal Himalaya

探测尼泊尔喜马拉雅山灾难性湖泊溃决的后果

基本信息

批准号：
243747290
负责人：
Professor Dr. Oliver Korup
金额：
--
依托单位：
Institut für Geowissenschaften
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2014
资助国家：
德国
起止时间：
2013-12-31 至 2018-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/243747290?language=en
关键词：
Detecting Legacy Catastrophic Lake Outbursts

项目摘要

In the Nepal Himalaya, the hazard from catastrophic lake outbursts linked to natural dams other than glacial, i.e. mostly those formed by landslides or debris flows, is virtually unknown. Yet peak discharge from historic lake bursts surpass hydrological flood peaks by up to two orders of magnitude, and some of the largest Holocene outburst flows on Earth may have originated in the orogen. Whether outburst events generally promote flushing of valley-floor sediments and enhance bedrock incision instead of catastrophically depositing debris remains unclear also. Yet geomorphic consequences of dam breaks undermine existing hazard appraisals of hydro-meteorological floods, where changes to channel geometry modulate flood frequencies for a given discharge. Elevated post-outburst sediment flux may impede maintenance of hydropower reservoirs and threaten water resources over years to decades, while ultimately accelerate or delay fluvial dissection of the Himalayan orogen in response to tectonic uplift.Very few studies have looked at Himalayan Quaternary archives from a hazard perspective, while the current focus on future sources and impacts of glacial lake outbursts is limited by short instrumental records. This proposal addresses this crucial research gap by quantifying from tell-tale deposits of different ages first-order sediment budgets of, and recovery rates from, selected outburst events. The aim is to investigate their geomorphic and sedimentary legacy on decadal to millennial timescales in order to better constrain hazard assessments, and improve our knowledge on recovery rates of Himalayan rivers from such extreme events. This approach integrates the scope of previous work by focussing on three distinct timescales: (1) Decadal-scale recovery of channels impacted by well-documented historic outbursts; (2) Centennial-scale recovery of rivers catastrophically infilled following dam breaks; and (3) Holocene re-incision of rivers that had been dammed for tens of millennia. Fieldwork in the Pokhara valley and the Khumbu Himal will be complemented by modelling of natural dam-break scenarios. Methods include geomorphic and sedimentary facies mapping from field and remote-sensing data; DGPS surveying; geomorphometric analysis and modelling; cosmogenic nuclide and radiocarbon dating; palaeoflood hydraulic modelling; and Bayesian data analysis for quantifying uncertainties.Expected results include sediment budgets and flow characteristics tied to recent and prehistoric lake bursts; new insights on the timing, mechanisms, and rates linked to some of the largest late Quaternary to historic natural dams and lakes in the Himalaya; and a customised GIS Web Service for locating the magnitudes of hypothetical lake outbursts compared to 1-in-a-100-year hydrological floods.

在尼泊尔喜马拉雅地区，与冰川以外的天然水坝有关的灾难性湖泊溃决的危险，即主要由山崩或泥石流形成的水坝，几乎是未知的。然而，历史上湖泊溃决的洪峰流量超过水文洪峰两个数量级，地球上一些最大的全新世溃决流量可能起源于造山带。爆发事件是否通常促进谷底沉积物的冲刷和增强基岩切割，而不是灾难性地沉积碎片，仍然不清楚。然而，溃坝的地貌后果破坏了现有的水文气象洪水的危险评估，其中通道几何形状的变化调节给定流量的洪水频率。升高后爆发的沉积物通量可能会阻碍水电水库的维护，并威胁水资源，在几年到几十年，而最终加速或延迟河流切割喜马拉雅造山带在响应构造uptection.Very少的研究看喜马拉雅第四纪档案从危险的角度来看，而目前的重点是未来的来源和影响的冰川湖爆发是有限的短仪器记录。这项建议解决了这一关键的研究空白，从不同年龄的一阶沉积物的预算和恢复率，选定的突出事件的指示存款量化。其目的是调查他们的地貌和沉积遗产的十年到千年的时间尺度，以更好地约束灾害评估，并提高我们的知识喜马拉雅河流从这种极端事件的恢复率。这种方法通过集中在三个不同的时间尺度上整合了以前工作的范围：（1）记录良好的历史爆发影响的通道的十年规模的恢复;（2）溃坝后灾难性填充的河流的百年规模的恢复;（3）已筑坝数万年的河流的全新世重新切割。在博卡拉河谷和昆布高原的实地工作将辅之以自然溃坝情景的模拟。方法包括根据实地和遥感数据绘制地貌和沉积相图;差分全球定位系统测量;地貌分析和建模;宇宙成因核素和放射性碳测年;古森林水力建模;以及用于量化不确定性的贝叶斯数据分析。对喜马拉雅地区一些最大的第四纪晚期自然大坝和湖泊的时间、机制和速率的新见解;和一个定制的地理信息系统网络服务，用于定位与百年一遇水文洪水相比的假设湖泊溃决的量级。