A First-of-Its-Kind Model of Bolivian GLOFs Projects Significant Risks

The rapid retreat of the world’s land ice means that glacial lakes — bodies of water formed by glacial meltwater — risk collapsing in potentially unexpected and catastrophic floods that threaten downstream communities.

University researchers in the United Kingdom and the United States have, for the first time, modeled the potential risk for glacial lake outburst floods, or GLOFs, for three lakes in the Bolivian Andes. Their results, published in December in the journal Natural Hazards, show that as many as 2,200 people could be impacted by flooding in six communities located downstream from each of the lakes. And, the researchers found, up to 2,100 people could be exposed to flooding of 2 meters or more, which “could be life threatening and cause a significant damage to infrastructure.”

The researchers focused on Pelechuco, Laguna Glaciar, and Laguna Arkhata, which are located within the Cordellera Oriental, Bolivia’s major mountain system.

Simon Cook of the University of Dundee in the United Kingdom and one of the authors of the study told GlacierHub that the researchers chose the lakes because a previous study they developed a technique for assessing GLOF risk.

Location of glaciers and potentially dangerous glacial lakes in the Bolivian Andes, as well as the 2009 Keara GLOF event. The risk of each glacial lake identified by Cook et al. (2016) was assessed by Kougkoulos et al. (2018) using the MCDA methodology; three lakes were graded as ‘medium’ (orange) and ‘high’ risk (red) and form the focus of this study. (Source: Natural Hazards)

“Using a carefully chosen set of criteria, we narrowed down 25 lakes that had been previously recognized to have the capacity to generate a damaging GLOF to three that were estimated to have ‘medium’ or ‘high’ GLOF risk,” he said. “These all have slightly different characteristics, but fundamentally they all sit up-stream from human settlements and are situated very close to either steep valley slopes or hanging glaciers that could shed debris or ice into the lakes, thereby generating an overtopping wave.”

The communities were Agua Blanca and Pelechuco, which are located downstream from Pelechuco, Sorata, which is downstream of Laguna Glaciar, and Totoral Pampa, Tres Rios, and Khanuma, which are located downstream from Laguna Arkhata.

Structures in Pelechuco are typically built of brick and topped with corrugated steel roofing.
(Credit: Dirk Hoffmann)
A view of Sorata, which lies downstream from Laguna Glaciar (Credit: Dirk Hoffmann)

The authors modeled water flows that might result from varying GLOF events. “This modeling approach has already been used to model GLOFs from Lake 513 in Peru and in Chilean Patagonia, as well as in other regions of the world,” Cook said.

To test the accuracy of their model, the researchers ran simulations of a 2009 GLOF that occurred in Keara, located in the Apolobamba region of Bolivia. The model proved to “reproduce realistic flood depths and inundations.”

The researchers modeled three GLOF scenarios that projected “optimistic,” “intermediate,” and “pessimistic” levels of drainage flows. They were then able to estimate the number of buildings and people that might be affected by a flood.

They found, in total, between 1,140 and 2,202 people could be affected if all of the lakes were to burst, and between 843 and 2,119 people could be exposed to flow depth of at least 2 meters. Between 510 and 979 buildings could be affected if all of the lakes were to burst, according to the researchers’ model.

Potentially affected population numbers per community and per modeled scenario. Left (optimistic), center (intermediate), and right (pessimistic). (Source: Natural Hazards)

Ioannis Kougkoulos of the University Nottingham in the United Kingdom and lead author of the study told GlacierHub in an email that economic or infrastructure concerns among residents often trump the risk of flooding. “So they cannot put all the focus on these low-frequency natural disasters,” he said.

Laguna Arkhata and Pelechuco lake, according to the authors, represent the greatest GLOF risk due to the large numbers of people who live in the potential flow paths.

To address these risks, the authors suggest cost-benefit analyses that consider community relocation, community awareness programs, and early-warning systems.

Read more on GlacierHub:

Photo Friday: Countdown to the Release of the IPCC’s Special Report on the Ocean and Cryosphere

New Research Reveals How Megafloods Shaped Greenland And Iceland

Observing Flora Near a Famous Norwegian Glacier


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