Modelling glacial lake outburst flood impacts in the Bolivian Andes

Abstract

The Bolivian Andes have experienced sustained and widespread glacier mass loss in recent decades. Glacier recession has been accompanied by the development of proglacial lakes, which pose a glacial lake outburst flood (GLOF) risk to downstream communities and infrastructure. Previous research has identified three potentially dangerous glacial lakes in the Bolivian Andes, but no attempt has yet been made to model GLOF inundation downstream from these lakes. We generated 2-m resolution DEMs from stereo and tri-stereo SPOT 6/7 satellite images to drive a hydrodynamic model of GLOF flow (HEC-RAS 5.0.3). The model was tested against field observations of a 2009 GLOF from Keara, in the Cordillera Apolobamba, and was shown to reproduce realistic flood depths and inundation. The model was then used to model GLOFs from Pelechuco lake (Cordillera Apolobamba) and Laguna Arkhata and Laguna Glaciar (Cordillera Real). In total, six villages could be affected by GLOFs if all three lakes burst. For sensitivity analysis, we ran the model for three scenarios (pessimistic, intermediate, optimistic), which give a range of ~ 1100 to ~ 2200 people affected by flooding; between ~ 800 and ~ 2100 people could be exposed to floods with a flow depth ≥ 2 m, which could be life threatening and cause a significant damage to infrastructure. We suggest that Laguna Arkhata and Pelechuco lake represent the greatest risk due to the higher numbers of people who live in the potential flow paths, and hence, these two glacial lakes should be a priority for risk managers.

The Geomorphic Impact of Outburst Floods: Integrating Observations and Numerical Simulations of the 2000 Yigong Flood, Eastern Himalaya

“…Outburst flood simulation can be a cost-effective tool for hazard assessment and mitigation planning in mountainous terrain (e.g., Allen et al, 2016;Bajracharya et al, 2007;Frey et al, 2018;Kougkoulos et al, 2018;Schneider et al, 2014;Shrestha et al, 2010;Wang et al, 2018). However, most such modeling has been limited to relatively small events (but c.f., Risley et al, 2006).…”

“…Some studies of ancient outburst floods have related simulated hydraulics to geomorphic features and deposits (e.g., Alho et al, 2010;Bohorquez et al, 2015;Denlinger & O'Connell, 2009;O'Connor, 1993;Komatsu et al, 2009;Larsen & Lamb, 2016;Miyamoto et al, 2006), and recent work on modern outburst floods has begun to examine relationships between hydraulics and geomorphology (e.g., Cook et al, 2018;Kougkoulos et al, 2018). Building on this prior work, we focus on the interaction of the flow with valley topography to address how outburst flood hydraulics relate to slackwater sand and boulder bar deposition, with implications for bed armoring and roughness relevant to long-term river incision.…”

Hazard Assessment for a Glacier Lake Outburst Flood in the Mo Chu River Basin, Bhutan

“…In addition to other features, this model can simulate two-dimensional unsteady river hydraulics. HEC-RAS was chosen, because it is freely available and has already delivered realistic results in other studies [18,22,23,25,26]. A full model description can be found in [27].…”

Lake Evolution, Hydrodynamic Outburst Flood Modeling and Sensitivity Analysis in the Central Himalaya: A Case Study

“…The HEC-RAS 1D model [39] was employed to model a series of potential GLOF events of Safed Lake. Despite that this tool has not been widely employed in Uttarakhand previously, it has been successfully employed in GLOF modeling (both reconstructing past GLOFs and modeling potential future GLOFs) in different geographical settings and contexts (e.g., [40][41][42]). As such, we were convinced this tool would provide physically plausible modeling results in our case too.…”