Climate Change Increases Flood Risk in Peru

The rising danger of glacial lake flooding in a warmer climate has important implications for humans and animal populations in Peru’s Cordillera Blanca. A recent study in CATENA by Adam Emmer et al. examined a large swath of nearly 900 high altitude Peruvian lakes in the mountainous Cordillera Blanca region, studying their susceptibility to outburst floods in light of modern climate change.

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A variety of glacial lake sizes in the Cordillera Blanca (Source: Elizabeth Balgord).

An outburst flood occurs when the dam containing glacial meltwater, usually comprised of either glacial ice or a terminal moraine (glacial debris lying at the edge of the glacier), fails. Glaciologist Mauri Pelto commented in the American Geophysical newsletter that the moraine dams are “just comprised of gravel, sand and clay dumped by the glacier” and “high water levels caused by upstream floods, avalanches or landslides can cause failure,” leading to major damage of the landscape. The team’s research elucidated that the incidence of glacial lake outburst flooding (GLOF) is increasing and the general distribution of alpine lakes is shifting upward in the region as temperatures warm. 

Knowing a lake’s size, configuration and type allows local water management in the Cordillera Blanca to be improved, according to Emmer et al. By mapping lakes with the classification of either moraine-dammed or bedrock-dammed, the team’s analysis can help local hydrological experts improve water management techniques for the changing distribution of alpine water. It also contributes to the scientific community’s overall understanding of ongoing environmental change.

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A large, high elevation glacial lake lying before the high Andes (Source: Elizabeth Balgord).

By studying the Cordillera Blanca region’s alpine lakes through a combination of remote sensing (high resolution aerial imagery and measurements) and field observations, Emmer’s team categorized 882 lakes by their size and altitude, ultimately referencing their findings with historical data to observe water redistribution over the last 60 years. Emmer et al. established that glacial lakes had expanded in size and number at higher elevations and disappeared at lower elevations since the 1951 study by Juan Concha in the same region. This finding confirms that environmental change and glacier retreat are strongly correlated in the high alpine.

Results from the analyses showed that from 1948 to 2013, lakes that remained in already deglaciated areas tended to be resilient and generally maintained water levels throughout the 65-year examination. Moraine-dammed lakes in particular resisted disappearing despite glacial retreat, suggesting that bodies of water dammed by materials other than ice were more adaptable to recently warmer temperatures. 

The team also noticed that despite the recent resiliency of moraine dammed lakes, glacial lake outburst flooding was caused predominantly by these dams in the early portion of the Cordillera Blanca’s glacial retreat, in the 1940s and 1950s. Flooding in more recent years has occurred in bedrock-dammed lakes. Although glacial lakes were recorded to have shifted from 4250-4600m in the late 1940s to predominantly above 4600m today, no statistically significant trend was established relating outburst flooding to any particular elevation.

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A research team gathered at the waters edge (Source: Elizabeth Balgord).

In order to reduce the risk of flood damage in local communities, Emmer et al. suggested continuous monitoring of young, developing proglacial lakes, using extensive flood modeling and outburst susceptibility assessments to account for future changes in the glacier. Understanding that the melting of glaciers is accelerating in a warming world, the need for more intensive local efforts in response to the threat of flooding is apparent.  

The Peruvian government has responded to high lake levels in the mountains of the Cordillera Blanca by “building tunnels and concrete pipes through the [weakest] moraines to allow lake drainage to safe levels,” according to Pelto. The government then rebuilds the moraines over the drainage system to strengthen it. By incorporating the monitoring techniques suggested by Adam Emmer, the government has the opportunity to manage and stay ahead of the flood risk as temperatures continue to rise. 

Glacial lake outburst flooding is hardly unique to the Peruvian landscape. This December, the Kathmandu Post illuminated the growing danger of GLOFs as the Nepalese Dhaulagiri Glacier recedes, creating a hazardous environment in the Mt. Nilgiri region. Researchers at the Chinese Institute of Mountain Hazards and Environment also established a strong link in Tibet between rising temperatures and glacial melting, contributing to more frequent and larger glacial lakes than in the past 50 years. With the growing number of alpine lakes and increased temperatures, ice dams are highly fragile and prone to failure.

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A variety of landscapes exist at different elevations in the Peruvian Andes (Source: Elizabeth Balgord).

Emmer et al.’s study offers an interesting evolutionary perspective on the state of the Cordillera Blanca. The study’s publication illustrates that even the planet’s most dramatic, seemingly unchangeable environments are plastic under the force of global climate change. The redistribution of alpine glacial lakes across the world’s mountainous regions indicates that the risk of outburst flooding should not be taken lightly. The team’s suggestions for future monitoring, to either mitigate the flooding hazard in populated regions or coordinate adaptation efforts, further illustrates the gravity of the situation. Although the risk of outburst flooding has only been studied in specific locations, the changing state of glacial lakes is already quantifiable and may be an effective proxy for monitoring the future extent of global warming.

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