Glacial Lake Outburst Floods (GLOFs)

Glacial Lake Outburst Floods (GLOFs)

Why in news:  Rising temperatures have increased the risk of glacial lake outbursts of the kind that devastated the Kedarnath Valley in 2013 and parts of Chamoli in 2021. Uttarakhand has initiated a GLOF risk assessment study.

Introduction

To address the growing threat of Glacial Lake Outburst Floods (GLOFs) – devastating events that have previously caused widespread damage in areas such as the Kedarnath Valley in 2013 and parts of Chamoli in 2021 – the Uttarakhand government has taken proactive steps. It has established two expert teams dedicated to assessing the risk associated with five glacial lakes considered potentially dangerous. These lakes are particularly vulnerable to GLOFs, a concern heightened by the devastating effects of similar past events in the Himalayan region.

The initiative is part of a broader risk assessment strategy aimed at reducing the likelihood of future GLOF incidents and ensuring that there is adequate time for relief operations and evacuation processes in the event of a lake breach. This effort is in line with the National Disaster Management Authority’s (NDMA) work, under the aegis of the Union Ministry of Home Affairs, which has flagged 188 glacial lakes across the Himalayan states as potential GLOF risks due to heavy rainfall, with 13 of these lakes located in Uttarakhand.

Global climate change has increased the risk of GLOFs. Rising global surface temperatures have caused glacial lakes to expand and increase in number, putting about 15 million people at risk of flash and severe flooding. These changes underline the urgent need for targeted risk assessment and mitigation strategies to protect vulnerable populations and infrastructure from the destructive force of GLOFs.

Glacial Lake Outburst Floods (GLOFs)

Glacial lake outburst flood (GLOF) is a type of flood that occurs when water in a glacial lake is suddenly released. These lakes form behind natural dams formed by ice or moraines (accumulations of glacial debris). GLOFs can release millions of cubic meters of water, causing massive floods downstream with the potential to destroy anything in their path.

Process of glacial lake formation

Glacial lakes form from a combination of glacial activity and naturally occurring material. As glaciers advance, they can block valleys with ice or moraine, forming a natural dam. Meltwater from glaciers or rainfall collects behind this dam, forming a lake. Over time, as the climate warms, the glaciers retreat and leave behind these dammed lakes.

Factors leading to GLOFs

Ice or moraine dam failure: The most common cause is lake dam failure. Such erosion may be caused by the melting of an ice dam or the weakening of a moraine dam over time.

Seismic activity: Earthquakes can destabilize a natural dam or lake ice cap, causing a sudden release of water.

Heavy rainfall or rapid melting: Heavy rainfall or unusually rapid melting of snow and ice can cause lakes to overflow, causing natural dams to break.

Ice or rock avalanche: An avalanche falling into a glacial lake can displace water so rapidly that it can break the dam.

Recent Data and Facts

In recent years, climate change has significantly affected glaciated areas, increasing the frequency and intensity of GLOFs. As glaciers melt at unprecedented rates, more glacial lakes are formed, and existing lakes become larger and more unstable.

This trend increases the risk of floods especially in areas such as the Himalayas, the Andes and parts of the Arctic. The International Center for Integrated Mountain Development (ICIMOD) has identified hundreds of potentially dangerous glacial lakes within the Himalayan region alone.

For example, a study published in “Nature Climate Change” in 2021 highlighted that the number of glacial lakes worldwide has increased by about 50% since the 1990s, directly linked to global warming. Is related to increase in temperature. This increase in the number and volume of glacial lakes increases the risk of GLOFs, posing a significant threat to millions of people living in vulnerable areas.

Notable GLOF Events Globally

1925, Coeur d’Alene Lake, United States: One of the early documented GLOFs occurred when a moraine-dammed lake in Idaho burst, causing significant damage.

1935, Sikkim, India: A GLOF from the Llonak Lake in Sikkim caused widespread destruction and loss of life, highlighting the dangers posed by these events in the Himalayan region.

1985, Armero Tragedy, Colombia: Perhaps one of the most tragic GLOFs occurred when the Nevado del Ruiz volcano’s eruption melted a glacier, causing an outburst flood that buried the town of Armero, killing more than 20,000 people.

1996, Iceland: A subglacial volcanic eruption melted part of the Vatnajökull glacier, leading to a massive GLOF. The flood waters carried icebergs up to 10 meters tall and destroyed bridges and roads, illustrating the power of GLOFs in cold volcanic regions.

2000, Bhutan: A GLOF from the Luggye Tso glacial lake in Bhutan unleashed around 45 million cubic meters of water, causing extensive damage to infrastructure and agriculture but was notable for the successful mitigation efforts that reduced human fatalities.

Global Impact of GLOFs

Geographical vulnerability

Himalayas: Known as a hotspot for GLOFs, this region has seen the most frequent GLOF events in high mountain Asia, especially the Karakoram Range. GLOFs have caused the loss of more than 7,000 lives over the past 190 years, with significant impacts on local communities, biodiversity, and infrastructure.

Andes: GLOFs have caused approximately 32,000 deaths in Peru alone during the 20th century, with significant impacts on downstream communities and infrastructure. Glacier shrinkage in the region has led to an increase in the number and size of glacial lakes, increasing the risk of future GLOFs.

North America: Areas of western Canada and the western United States also experienced GLOFs, causing ecological and geomorphic disturbances, including destroyed vegetation, alluvial fans, and impacts on aquatic wildlife.

Factors Contributing to Regional Vulnerabilities

The increasing number of GLOFs is linked to climate change, which is causing glaciers to retreat and form new glacial lakes. Other contributing factors include:

Physical geography: The topography of regions such as the Himalayas and the Andes, where steep slopes and large glacial lakes are common, increases the risk of GLOF events.

Climate change: Warmer temperatures contribute to the melting of glaciers, leading to the formation and growth of glacial lakes behind unstable natural dams.

Human activity: Expansion into glaciated catchments and development of infrastructure in high-risk areas have further increased vulnerability to GLOFs.

Socioeconomic impact

Loss of life: GLOFs have caused thousands of deaths in affected areas, particularly in high-mountain Asia and the Andes.

Damage to infrastructure: Roads, bridges, and hydropower developments are particularly vulnerable to sudden and massive water discharges from GLOFs.

Economic costs: Destruction of agricultural land, livestock, and property could result in millions of dollars in losses, with a severe impact on the local economy.

Long-term displacement and agricultural disruption: GLOF-affected communities may face long-term displacement, and destruction of agricultural lands could disrupt local food supplies and livelihoods.