Abstract:Lake outburst and debris flow disaster at Kedarnath, June 2013: hydrometeorological triggering and topographic predisposition Abstract Heavy rainfall in June 2013 triggered flash flooding and landslides throughout the Indian Himalayan state of Uttarakhand, killing more than 6000 people. The vast majority of fatalities and destruction resulted directly from a lake outburst and debris flow disaster originating from above the village of Kedarnath on June 16 and 17. Here, we provide a systematic analysis of the co… Show more
“…The expansion of existing lakes and formation of new lakes will increase the potential for mass movements of ice or rock to trigger GLOF events, and new GLOF paths will increase the downstream potentially affected land area. The Tehsil of Kullu (K), within the central District of Kullu is identified thousands of people has highlighted that extreme hydrometeorological conditions can trigger catastrophic GLOFs (Singh et al 2014;Allen et al 2015), yet knowledge on how such conditions may change in the future is limited by uncertainty in regional climate projections. Baseline information on permafrost distribution in the Kullu District has recently been established ), but ground temperature measurements and further field validation is required before the implications of thawing permafrost on GLOF stability can be reasonably quantified and integrated into a hazard assessment.…”
Glacial lake outburst floods (GLOFs) are a serious and potentially increasing threat to livelihoods and infrastructure in most high-mountain regions of the world. Here, we integrate modelling approaches that capture both current and future potential for GLOF triggering, quantification of affected downstream areas, and assessment of the underlying societal vulnerability to such climate-related disasters, to implement a first-order assessment of GLOF risk across the Himalayan state of Himachal Pradesh (HP), Northern India. The assessment thereby considers both current glacial lakes and modelled future lakes that are expected to form as glaciers retreat. Current hazard, vulnerability, and exposure indices are combined to reveal several risk 'hotspots', illustrating that significant GLOF risk may in some instances occur far downstream from the glaciated headwaters where the threats originate. In particular, trans-national GLOFs originating in the upper Satluj River Basin (China) are a threat to downstream areas of eastern HP. For the future deglaciated scenario, a significant increase in GLOF hazard levels is projected across most administrative units, as lakes expand or form closer towards steep headwalls from which impacts of falling ice and rock may trigger outburst events. For example, in the central area of Kullu, a 7-fold increase in the probability of GLOF triggering and a 3-fold increase in the downstream area affected by potential GLOF paths can be anticipated, leading to an overall increase in the assigned GLOF hazard level from 'high' to 'very high'. In such instances, strengthening resilience and capacities to reduce the current GLOF risk will provide an important first step towards adapting to future challenges.
“…The expansion of existing lakes and formation of new lakes will increase the potential for mass movements of ice or rock to trigger GLOF events, and new GLOF paths will increase the downstream potentially affected land area. The Tehsil of Kullu (K), within the central District of Kullu is identified thousands of people has highlighted that extreme hydrometeorological conditions can trigger catastrophic GLOFs (Singh et al 2014;Allen et al 2015), yet knowledge on how such conditions may change in the future is limited by uncertainty in regional climate projections. Baseline information on permafrost distribution in the Kullu District has recently been established ), but ground temperature measurements and further field validation is required before the implications of thawing permafrost on GLOF stability can be reasonably quantified and integrated into a hazard assessment.…”
Glacial lake outburst floods (GLOFs) are a serious and potentially increasing threat to livelihoods and infrastructure in most high-mountain regions of the world. Here, we integrate modelling approaches that capture both current and future potential for GLOF triggering, quantification of affected downstream areas, and assessment of the underlying societal vulnerability to such climate-related disasters, to implement a first-order assessment of GLOF risk across the Himalayan state of Himachal Pradesh (HP), Northern India. The assessment thereby considers both current glacial lakes and modelled future lakes that are expected to form as glaciers retreat. Current hazard, vulnerability, and exposure indices are combined to reveal several risk 'hotspots', illustrating that significant GLOF risk may in some instances occur far downstream from the glaciated headwaters where the threats originate. In particular, trans-national GLOFs originating in the upper Satluj River Basin (China) are a threat to downstream areas of eastern HP. For the future deglaciated scenario, a significant increase in GLOF hazard levels is projected across most administrative units, as lakes expand or form closer towards steep headwalls from which impacts of falling ice and rock may trigger outburst events. For example, in the central area of Kullu, a 7-fold increase in the probability of GLOF triggering and a 3-fold increase in the downstream area affected by potential GLOF paths can be anticipated, leading to an overall increase in the assigned GLOF hazard level from 'high' to 'very high'. In such instances, strengthening resilience and capacities to reduce the current GLOF risk will provide an important first step towards adapting to future challenges.
“…Prior to 9 June, there was no significant rainfall, but a discharge rate varied from 54 to 65 m 3 /s, suggestive of runoff from glacier and snowmelt. The satellite-based imageries indicated that, in winter 2013, there was increase in snowfall of 30% in the Alaknanda and Mandakini catchment area [59,60]. Previous studies reported that the extreme rainfall in June has caused an acceleration of snowmelt-runoff and accumulation of large volume of water in the Lake [52,61].…”
Abstract:The extreme rainfall event during June 2013 in the Western Himalayas caused widespread flash floods, which triggered landslides, a lake-outburst, and debris flow. For the hydrological study of such an unexpected extreme event, it is essential to have reliable and accurate rainfall predictions based on satellite observations. The mountainous state of Uttarakhand is covered by complex topography, and this state has few, unevenly distributed, rain gauge networks. This unique study was conducted to evaluate three satellite based rainfall products (i.e., TMPA-3B42, Global Satellite Mapping of Precipitation (GSMaP), and NOAA CPC Morphing Technique (CMORPH)) against the observed rain gauge-based India Meteorological Department (IMD) gridded dataset for this rainfall episode. The results from this comprehensive study confirmed that the magnitude of precipitation and peak rainfall intensity were underestimated in TMPA-3B42 and CMORPH against gauge-based IMD data, while GSMaP showed dual trends with under-and over-predictions. From the results of the statistical approach on the determination of error statistic metrics (MAE (mean absolute error), NRMSE (normalized root mean square error), PBIAS (percent bias), and NSE (Nash-Sutcliffe efficiency)) of respective satellite products, it was revealed that TMPA-3B42 predictions were more relevant and accurate compared to predictions from the other two satellite products for this major event. The TMPA-3B42-based rainfall was negatively biased by 18%. Despite these caveats, this study concludes that TMPA-3B42 rainfall was useful for monitoring extreme rainfall event in the region, where rain-gauges are sparse.
“…Torrential rains rapidly raised the water level of the moraine-dammed Chorabari Lake, Uttarakhand, India, in June 2013. The dam breached and released 400 000 m 3 of water into the already flooded Mandakini River, inundating the pilgrimage city of Kedarnath (Allen et al 2015), and severely damaging at least two HPP sites downstream (Sandrp 2013). The recognition that GLOFs can substantially exceed design floods of HPP at the risk of damage or complete inoperability (Richardson and Reynolds 2000) hinges on a handful of case studies, but the regional picture of GLOF exposure remains illdefined.…”
Himalayan water resources attract a rapidly growing number of hydroelectric power projects (HPP) to satisfy Asia's soaring energy demands. Yet HPP operating or planned in steep, glacier-fed mountain rivers face hazards of glacial lake outburst floods (GLOFs) that can damage hydropower infrastructure, alter water and sediment yields, and compromise livelihoods downstream. Detailed appraisals of such GLOF hazards are limited to case studies, however, and a more comprehensive, systematic analysis remains elusive. To this end we estimate the regional exposure of 257 Himalayan HPP to GLOFs, using a flood-wave propagation model fed by Monte Carlo-derived outburst volumes of >2300 glacial lakes. We interpret the spread of thus modeled peak discharges as a predictive uncertainty that arises mainly from outburst volumes and dam-breach rates that are difficult to assess before dams fail. With 66% of sampled HPP are on potential GLOF tracks, up to one third of these HPP could experience GLOF discharges well above local design floods, as hydropower development continues to seek higher sites closer to glacial lakes. We compute that this systematic push of HPP into headwaters effectively doubles the uncertainty about GLOF peak discharge in these locations. Peak discharges farther downstream, in contrast, are easier to predict because GLOF waves attenuate rapidly. Considering this systematic pattern of regional GLOF exposure might aid the site selection of future Himalayan HPP. Our method can augment, and help to regularly update, current hazard assessments, given that global warming is likely changing the number and size of Himalayan meltwater lakes.
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