CLOUDBURSTS: Causes, Impact, & Prevention Tips

Recently, a cloudburst in Himachal Pradesh caused flash floods that left numerous individuals dead and several more missing. According to officials, these floods caused a great deal of damage, including the washing away of multiple buildings, bridges, and roadways.

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CLOUDBURST

• The India Meteorological Department (IMD) defines cloudbursts as abrupt, intense rainstorms that cover an area of roughly 10 square kilometers and produce more than 10 cm of rain in less than an hour. They frequently take place in hilly regions, particularly in the Himalayas.
• It usually happens in the Indian Subcontinent when a monsoon cloud moves from the Arabian Sea or the Bay of Bengal toward the north, passing over the plains and eventually reaching the Himalaya, where it can occasionally bring 75 mm of rain every hour.

WHAT ARE THE MAIN CAUSES OF CLOUDBURST?

• When hot air currents rise too strongly to allow raindrops to fall, they burst into larger droplets while smaller ones form below.
• This causes a large amount of water to build up in the atmosphere, which is suddenly released when the upward currents become less.
• Because of the intricate terrain of the Indian subcontinent, which promotes orographic lifting, cloudbursts are common in the region's hilly and mountainous areas.
• When air moves up a mountain's windward side, it rises and cools, a process known as orographic lifting.
• As moist air rises over the mountains, this mechanism intensifies cloud formation and precipitation; monsoon dynamics and regional weather patterns also have an impact on these high precipitation occurrences.

DISTINGUISHING BETWEEN CLOUDBURST AND RAINFALL

• Rain is condensed water falling from a cloud while cloudburst is a sudden heavy rainstorm.
• Rain over 10 cm per hour is categorized as a cloudburst.
• The cloudburst is a natural phenomenon, but occurs quite unexpectedly, very abruptly, and rather drenching.

EXAMPLES OF CLOUDBURSTS

• Uttarakhand Cloudburst (July 2021): Devastating cloudbursts in Chamoli, Uttarkashi, and Pithoragarh caused flash floods, landslides, and extensive damage to infrastructure and lives.
• Himachal Pradesh Cloudburst (August 2020): Cloudbursts in Kullu, Lahaul-Spiti, and Kinnaur triggered landslides and flash floods, damaging roads, bridges, and houses.

WHAT ARE THE EFFECTS OF CLOUDBURSTS?

• Flash floods: Flash floods are sudden, localized surges in water levels during or after intense rainfall.

  • Flash flooding starts within 6 or 3 hours of heavy rainfall. Intense thunderstorms typically cause it but can also result from dam or levee breaks and mudslides.
  • Factors like rainfall intensity, location, land use, topography, vegetation, soil type, and water content determine the speed and location of flash flooding.

• Landslides: A landslide is a mass movement of material, such as rock, earth or debris, down a slope. It can happen suddenly or more slowly over long periods of time.

  • Factors like heavy rainfall, erosion, and weathering can trigger landslides.
  • In India, landslides account for about 8% of global fatalities, with 847 deaths and thousands displaced from 2001 to 2021, according to research from IIT-Madras.
  • Around 13.17% of India’s area is susceptible to landslides, with 4.75% designated as "very highly susceptible."
  • Sikkim is the most prone state, while Kerala has over 14% of its land in the very high susceptibility category.

• Mudflows: It is a type of water flow characterized by its high density and viscosity, containing significant amounts of suspended particles and silt.

  • Mudflow can only transport and deposit the coarsest materials, leading to irreversible sediment entrainment, and it typically does not flow as far as regular water streams.

IMPACT OF CLIMATE CHANGE ON CLOUDBURST

• Increased Atmospheric Moisture: Rising global temperatures allow the atmosphere to hold more moisture. This moisture-laden air can lead to more intense cloud formation and increased potential for cloudbursts, especially in mountainous areas like the Himalayas.

• Changes in Precipitation Patterns: Climate change can shift precipitation patterns, causing some regions to experience prolonged dry periods while others face more intense rainfall events.

• Altered Atmospheric Stability: Higher temperatures can destabilize the atmosphere, leading to increased convective activity and more frequent thunderstorms, which are often linked to cloudbursts.

• Glacier Retreat and Snowmelt: Melting glaciers in regions like the Himalayas, driven by rising temperatures, are releasing water more quickly, potentially contributing to cloudburst events.

• Land Use Changes: Human activities such as deforestation and urbanization can alter local climates and precipitation patterns, affecting microclimates in mountainous areas and potentially influencing cloudburst occurrences.

HOW CAN WE PREVENT CLOUDBURST?

Ways to mitigate the devastating impact of cloudbursts:

• Early Warning Systems: Develop effective early warning systems to predict cloudbursts and provide timely alerts, allowing people to prepare and evacuate if necessary.
• Urban Planning and Infrastructure: Invest in resilient urban planning and infrastructure, such as stormwater drainage systems, retention ponds, and green spaces, to manage excess water and reduce flooding.
• Watershed Management: Implement practices to manage watersheds, like reducing soil erosion and increasing soil infiltration, to help control water flow and lessen the impact of cloudbursts.
• Reforestation and Green Infrastructure: Plant trees and maintain green areas to absorb excess water, reduce soil erosion, and stabilise slopes, helping to mitigate cloudburst effects.
• Awareness and Education: Educate communities about cloudburst risks and train them on response and evacuation procedures to ensure they take necessary precautions.
• Sustainable Land Use Practices: Promote land use practices that reduce vulnerability to cloudbursts, such as avoiding construction in flood-prone areas, controlling deforestation, and implementing soil conservation measures.
• International Cooperation: Work with neighbouring countries and international organisations to share best practices, technology, and resources for managing cloudbursts, especially in shared river basins.