Browsing by Subject "GLOF"

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Climate change adaptation to increasing isk of glacial lake outburst floods : decision making methodology for risk management applied to Imja Lake in Nepal and Lake Palcacocha in Peru
(2016-08) Cuéllar, Amanda Dulcinea; McKinney, Daene C.; Stahl, Dale O; Passalacqua, Paola; Webber, Michael E; Gilbert, Robert
Glacial retreat around the world, accelerated by climate change, has led to the formation of glacier lakes that present a risk of a glacial lake outburst flood (GLOF). GLOFs are sudden, catastrophic events that are impossible to predict. Communities in the path of a potential GLOF are now attempting to implement adaptation projects, yet no quantitative data or guidance is available to understand the benefits of adaptation projects or how to weigh these benefits against the cost of project implementation. The objective of this work is to develop a rational decision making methodology for GLOF risk management that incorporates available scientific information and the uncertainty surrounding the understanding of GLOF events. The decision making methodology consists of 1) identifying flooding scenarios, 2) evaluating the consequences of flooding scenarios, and 3) a nuanced (in terms of the inclusion of intangibles and probabilistic events) economic analysis of flood consequences and adaptation options. The methodology is applied to Lake Palcacocha in Peru and Imja Lake in Nepal to demonstrate the robustness of the methodology in light of different sources of uncertainty and data gaps. For Imja Lake it is concluded that lowering the lake 10 m is the best decision, from an economic standpoint. Nonetheless, the decision is sensitive to changes in the decision tree variables, which should be assessed for accuracy. At Lake Palcacocha it was determined that a GLOF would result in substantial damage to the city of Huaraz and the best decision is to lower the lake 30 m and install an emergency warning system (EWS). This decision is robust to large changes in the uncertain variables.
Ground penetrating radar survey for risk reduction at Imja Lake, Nepal
(Center for Research in Water Resources, University of Texas at Austin, 2012-10) Somos-Valenzuela, Marcelo; McKinney, Daene C.; Byers, Alton C.; Voss, Katalyn; Moss, Jefferson; McKinney, James C.
Hydropower site study at Imja Lake and Dingboche Village
(Center for Research in Water Resources, University of Texas at Austin, 2011-06) Allard, Jason; McKinney, Daene C.
Inundation Modeling of a Potential Glacial Lake Outburst Flood in Huaraz, Peru
(Center for Research in Water Resources, University of Texas at Austin, 2014-03) Somos-Valenzuela, Marcelo A.; Chisolm, Rachel E.; McKinney, Daene C.; Rivas, Denny
One of the consequences of recent glacier recession is the formation and rapid growth of lakes formed at the snout of glaciers. One risk is that moraines damming these glacial lakes could fail releasing a huge volume of water and creating a glacial lake outburst flood. This happened December 13, 1941, at Lake Palcacocha, Peru, flooding the city of Huaraz and killed several thousand people. Recently Lake Palcacocha has been declared in a state of emergency state because its volume has again reached dangerous levels, threatening a flood that would quickly reach Huaraz causing major devastation and potentially loss of life. An analysis has been performed of the glacial hazards for the city of Huaraz from Lake Palcacocha. This analysis consists of physical models of each process in the chain of events that results in a glacial lake outburst flood: rock and ice avalanche; wave generation, propagation and moraine overtopping; terminal moraine breaching and draining of the lake; and downstream inundation and impacts in the city of Huaraz. Two scenarios of moraine erosion were simulated: a worst-case event of a 56 m breach and a smaller 22.5 m erosion event. These scenarios showed that flood reaches the City of Huaraz 1.06 and 1.20 hours after the avalanche for the 56 m and 22.5 m events, respectively. The inundation in the city is extensive in both breaching events with depths exceeding 1 m in many areas, especially near the channel of the Quillcay River, and the velocity of the flood exceeding 1 m/s in most of this area. Because of the inundation depth and the velocity of the flow, most of the area of the city that experiences flooding will have a very high hazard level, putting both lives and property at risk.
Modeling and risk assessment of glacial lake outburst floods (GLOFs) : a case study of Imja Tsho in the Nepal Himalayas
(2018-01-26) Lala, Jonathan Matthew; McKinney, Daene C.
The Himalayas of South Asia are home to many glaciers, which are retreating because of climate change and leaving in their wakes large lakes. These lakes are held in place by naturally deposited and inherently unstable moraine dams, which are at risk of overtop by impulse waves, commonly generated when avalanches or landslides enter the lake. When an overtopping event causes catastrophic failure, a glacial lake outburst flood (GLOF) occurs. The Imja glacier is experiencing the highest mass loss rate in the Mount Everest region, contributing to the expansion of Imja Tsho, a lake with several villages downstream. A GLOF from the lake can bring catastrophic damage to these villages, threatening both property and human life and creating a need to understand the processes that trigger these floods. The process chain for an avalanche-induced GLOF was modeled numerically, using the output of one subprocess as input into the next. First, the volume and momentum of various avalanches entering the lake were calculated using RAMMS. Next, the subsequent waves were simulated using BASEMENT software and validated with empirical equations to ensure the proper transfer of momentum from the avalanche to the lake. BASEMENT was then used to model moraine erosion and downstream flooding, which yielded a map of risk areas downstream. Moraine erosion was calculated for two geomorphologic scenarios: a site-specific scenario using field data, and a worst-case scenario based on past literature and applicable to lakes in the entire region. Neither case resulted in flooding outside the river channel at downstream villages. The worst-case scenario resulted in some moraine erosion and increased channelization of the lake outlet, which yielded greater discharge downstream but no catastrophic collapse. The site-specific scenario generated similar results, but with very little erosion and a smaller downstream discharge. Results indicated that Imja Tsho is unlikely to produce a catastrophic GLOF in the near future; however, some risk exists within the river channel, necessitating continued monitoring of the lake. Furthermore, these models were designed for ease and flexibility so that they can be adopted by a wide range of stakeholders and appropriated for other lakes in the region.
Modeling Mitigation Strategies for Risk Reduction at Imja Lake, Nepal
(Center for Research in Water Resources, University of Texas at Austin, 2013-08) Somos-Valenzuela, Marcelo A.; McKinney, Daene C.; Byers, Alton C.; Rounce, David R.; Portocarrero, Cesar
A model was developed to assess the impact of a potential glacial lake outburst flood (GLOF) from Imja Lake in Nepal and its impact on downstream communities. Implications of proposed GLOF risk reduction alternatives, including one suggested by local community members, were assessed. Results provided three alternatives that offer significant risk reduction for the communities, including (1) no lowering of the lake and constructing a 60 m flood detention dam, resulting in a 43.2 percent reduction of risk, (2) lowering the lake 10 m with a 40 m dam, resulting in a 57.8 percent reduction of risk, and (3) lowering the lake 20 m with no dam, resulting in a risk reduction of 66.7 percent. An alternative to lower the lake by 3 m with no check-dam, currently under consideration by the Government of Nepal, would result in a 5.2 percent reduction of risk. This alternative does not appear to offer significant risk reduction benefits to downstream communities compared to lowering the lake by 20 m. Results suggest that either the lake must be lowered by significantly more than 3 m (20 m is recommended) or that a downstream flood detention dam be included in the project. One possible method of lowering Imja Lake is to use siphons to drain lake water by 3 m, excavate to the new water level, repeating the process until a total lowering of 20 m is achieved. This method would require the use of 13 pipes of 0.350 m diameter to lower the lake.
Vulnerability and decision risk analysis in glacier lake outburst floods (GLOF). Case studies : Quillcay sub basin in the Cordillera Blanca in Peru and Dudh Koshi sub basin in the Everest region in Nepal
(2014-08) Somos-Valenzuela, Marcelo A.; McKinney, Daene C.
Glacial-dominated areas pose unique challenges to downstream communities in adapting to recent and continuing global climate change, including increased threats of glacial lake outburst floods (GLOFs) that have substantial impacts on regional social, environmental and economic systems increasing risk due to flooding of downstream communities. In this dissertation, two lakes with potential to generate GLOFs were studied, Imja Lake in Nepal and Palcacocha Lake in Peru. At Imja Lake, basic data was generated that allowed the creation of a conceptual model of the lake. Ground penetrating radar and bathymetric surveys were performed. Also, an inundation model was developed in order to evaluate the effectiveness of a project that seeks to reduce flooding risk by lowering the lake at least 3 meters. In Peru, a GLOF inundation model was created. Also, the vulnerability of the people living downstream in the City of Huaraz was calculated, and the impacts of an early warning system were evaluated. The results at Imja indicated that the lake deepened from 98 m in 2002 to 116 m in 2012. Likewise, the lake volume increased from 35.8 to 61.6±1.8 million m3 over the past decade. The GPR survey at Imja and Lhotse-Shar glaciers shows that the glacier is over 200 m thick in the center of the glacier. The modeling work at Imja shows that the proposed project will not have major impacts downstream since the area inundated does not reduce considerably unless the lake is lowered by about 20 m. In Huaraz, the results indicate that approximately 40646 people live in the potentially inundated area. Using the flow simulation and the Peru Census 2007, a map of vulnerability was generated indicating that the most vulnerable areas are near the river. Finally, the potential number of fatalities in a worst case GLOF scenario from Lake Palcacocha was calculated to be 19773 with a standard deviation of 1191 if there is no early warning system and 7344 with a standard deviation of 1446 people if an early warning system is installed. Finally, if evacuation measures are improved the number reduces to 2865 with a standard deviation of 462.