Assessing downstream flood impacts due to a potential GLOF from Imja Tsho in Nepal

Somos‐Valenzuela, Marcelo; McKinney, Daene C.; Byers, Alton C.; Rounce, David; Portocarrero, César; Lamsal, Damodar

doi:10.5194/hess-19-1401-2015

Cited by 54 publications

(68 citation statements)

References 32 publications

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“…Everest (Figure 1). Several communities exist in the region and rely on agriculture and tourism for their income [18]. In this study, we focus on the community of Dingboche, which is approximately 7 km downstream from Imja Lake.…”

Section: Study Areamentioning

confidence: 99%

“…Rounce et al [23], found that Imja Lake was of moderate risk at that time due to its low hazard ranking and high downstream impact potential, but that the hazard and risk of the lake will likely increase over the next few decades if the lake continues to grow at its current rate. Despite the disagreement over the danger posed by Imja Lake, researchers have conducted numerous studies to understand how a GLOF from the lake would affect areas downstream [2,18,23]. Other studies of the lake have also focused on lake characteristics [25], moraine and glacier characteristics [31], and melting of source glaciers [32].…”

Section: Study Areamentioning

confidence: 99%

“…In particular, only one study has attempted to quantify possible GLOF inundation severity from Imja Lake with various levels of lake lowering remediation [18]. In addition, no other work has quantified the range of potential fatalities or direct economic impacts of an Imja Lake GLOF with and without mitigation measures.…”

Section: Introductionmentioning

confidence: 99%

“…By lowering the lake level, pressure on the moraine decreases and the potential surge of water flowing downstream in the event of a flood is decreased, resulting in a smaller inundated area [7,13,18]. A less costly and invasive option is to install early warning systems and community outreach efforts.…”

Section: Introductionmentioning

confidence: 99%

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Decision-Making Methodology for Risk Management Applied to Imja Lake in Nepal

Cuéllar

McKinney

2017

Water

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Glacial retreat causes the formation of glacier lakes with the potential of producing glacial lake outburst floods (GLOFs). Imja Lake in Nepal is considered at risk for a GLOF. Communities in the path of a potential Imja GLOF are implementing adaptation projects, yet no quantitative data or guidance is available to understand the benefits of these projects or how to weigh benefits against the cost of implementation. We develop and demonstrate a decision-making methodology for GLOF risk management, incorporating available scientific information and uncertainty. The methodology consists of (1) identifying flooding scenarios, (2) evaluating scenario consequences, and (3) performing an economic analysis of proposed adaptation projects. The methodology is applied to assess benefits in Dingboche of lowering Imja Lake by 3, 10 and 20 m. The results show that the baseline case (no lake lowering) has the lowest expected cost because of low valuation of agricultural land and homes in the literature. Nonetheless, the result is sensitive to changes in the analysis variables. We also found that lowering the lake by 10 or 20 m is efficient according only to the methodology used here; however, considering only direct economic damages and literature cost estimates, the costs outweigh the benefits for these projects.

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Section: Study Areamentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Decision-Making Methodology for Risk Management Applied to Imja Lake in Nepal

Cuéllar

McKinney

2017

Water

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“…One-dimensional models based on the St. Venant equations have been used to model the downstream flood wave propagation of a GLOF, e.g., Klimes et al (2013), who used HEC-RAS (USACE, 2010) to reproduce the 2010 GLOF from Lake 513 in Peru, Cenderelli and Wohl (2003), who used HEC-RAS to reproduce steady-state aspects of GLOFs in the Khumbu region of Nepal, Byers et al (2013), who used HEC-RAS to model a potential GLOF from Lake 464 in the Hongu valley of Nepal, Meon and Schwarz (1993), who used DAMBRK (Fread, 1988) to model a potential GLOF in the Arun valley of Nepal, and Bajracharya et al (2007), who used FLDWAV (NWS, 1998 to model a potential GLOF from Imja Lake in Nepal. Two-dimensional SWE models are often used to model downstream impacts of GLOFs, e.g., Worni et al (2012), who used BASEMENT to model flooding from a GLOF at Shako Cho Lake in India, Schneider et al (2014), who used RAMMS to model debris flow from an overtopping wave at Lake 513 in Peru, Somos-Valenzuela et al (2015), who used FLO2D to model downstream inundation from a potential GLOF at Imja Lake in Nepal, and Mergili et al (2011), who used RAMMS and FLO2D to simulate flooding from Lake Khavraz in Tajikistan. FLO2D (2012) is used here to simulate the downstream inundation.…”

Section: Introduction To Glacial Lake Hazard Process Chain Modelingmentioning

confidence: 99%

Modeling a glacial lake outburst flood process chain: the case of Lake Palcacocha and Huaraz, Peru

Somos‐Valenzuela

Chisolm

Rivas

et al. 2016

Hydrol. Earth Syst. Sci.

101

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Abstract. One of the consequences of recent glacier recession in the Cordillera Blanca, Peru, is the risk of glacial lake outburst floods (GLOFs) from lakes that have formed at the base of retreating glaciers. GLOFs are often triggered by avalanches falling into glacial lakes, initiating a chain of processes that may culminate in significant inundation and destruction downstream. This paper presents simulations of all of the processes involved in a potential GLOF originating from Lake Palcacocha, the source of a previously catastrophic GLOF on 13 December 1941, killing about 1800 people in the city of Huaraz, Peru. The chain of processes simulated here includes (1) avalanches above the lake; (2) lake dynamics resulting from the avalanche impact, including wave generation, propagation, and run-up across lakes; (3) terminal moraine overtopping and dynamic moraine erosion simulations to determine the possibility of breaching; (4) flood propagation along downstream valleys; and (5) inundation of populated areas. The results of each process feed into simulations of subsequent processes in the chain, finally resulting in estimates of inundation in the city of Huaraz. The results of the inundation simulations were converted into flood intensity and preliminary hazard maps (based on an intensity-likelihood matrix) that may be useful for city planning and regulation. Three avalanche events with volumes ranging from 0.5 to 3 × 10 6 m 3 were simulated, and two scenarios of 15 and 30 m lake lowering were simulated to assess the potential of mitigating the hazard level in Huaraz. For all three avalanche events, three-dimensional hydrodynamic models show large waves generated in the lake from the impact resulting in overtopping of the damming moraine. Despite very high discharge rates (up to 63.4 × 10 3 m 3 s −1 ), the erosion from the overtopping wave did not result in failure of the damming moraine when simulated with a hydromorphodynamic model using excessively conservative soil characteristics that provide very little erosion resistance. With the current lake level, all three avalanche events result in inundation in Huaraz due to wave overtopping, and the resulting preliminary hazard map shows a total affected area of 2.01 km 2 , most of which is in the high hazard category. Lowering the lake has the potential to reduce the affected area by up to 35 %, resulting in a smaller portion of the inundated area in the high hazard category.

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New hybrid method for vulnerability assessment in floodplain areas exposed to dam break

Nekooie

Gholizadeh

2023

Engineering Reports

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Natural and man‐made factors can cause dam failure, which constantly threatens downstream assets. Flood risk assessment is typically developed according to the hydraulic and geographic characteristics of floodplain regions. However, previous approaches have not considered asset values and the impacts of flooding on them, including threat probability and consequences. This report presents a new integrated hybrid model based on security vulnerability assessment and hydraulic analysis of floods and uses the source‐pathway‐receptor‐consequences (SPRC) approach to comprehensively examine all factors. A questionnaire survey was used for performing threat analysis and attractiveness analysis and determining the asset values and consequences. A geographical information system was applied to superimpose layers based on the SPRC approach in five different scenarios based on piping discharge and downstream flow in the case of a dam break. These scenarios were developed considering the basin water level. The results illustrate that residential areas have the highest vulnerability, and farmlands exhibit the lowest exposure to flooding caused by dam failure. Based on the attraction to terrorism, criticality due to consequences, and flooding characteristics, high‐risk zones were identified for implementing mitigation or protection countermeasures.

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Assessing downstream flood impacts due to a potential GLOF from Imja Tsho in Nepal

Cited by 54 publications

References 32 publications

Decision-Making Methodology for Risk Management Applied to Imja Lake in Nepal

Decision-Making Methodology for Risk Management Applied to Imja Lake in Nepal

Modeling a glacial lake outburst flood process chain: the case of Lake Palcacocha and Huaraz, Peru

New hybrid method for vulnerability assessment in floodplain areas exposed to dam break

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