Cloudbursts in Himachal Pradesh | 03 Aug 2024

Source: IE

Why in News?

Recently, a cloudburst, leading to flash floods in Himachal Pradesh has killed many people and several missing.

• These floods caused significant destruction, including the washing away of several buildings, bridges, and roads, according to officials.

What is a Cloudburst?

• About:
  • According to the India Meteorological Department (IMD), cloudbursts are sudden, heavy rainstorms where more than 10 cm of rain falls in less than an hour over a small area, of about 10 square km. They often happen in mountainous areas, especially in the Himalayas.
  • In the Indian Subcontinent, it generally occurs when a monsoon cloud drifts northwards, from the Bay of Bengal or the Arabian Sea across the plains then on to the Himalaya which sometimes brings 75 mm of rain per hour.
• Causes:
  • Cloudbursts occur when strong upward currents of hot air prevent raindrops from falling, allowing them to grow larger while new smaller drops form below.
  • This leads to a significant accumulation of water in the atmosphere, which is released abruptly when the upward currents weaken.
  • Cloudbursts frequently occur in the hilly and mountainous areas of the Indian subcontinent, largely due to the region's complex topography, which facilitates orographic lifting.
    • Orographic lifting occurs when air rises and cools as it travels up the windward side of a mountain.
    • This process enhances cloud development and rainfall as moist air ascends over the mountains, with monsoon dynamics and localised weather patterns further influencing these intense precipitation events.
• Cloudburst are Different from Rainfall:
  • Rain is condensed water falling from a cloud while cloudburst is a sudden heavy rainstorm.
  • Rain over 10 cm per hour is categorised as a cloudburst.
  • The cloudburst is a natural phenomenon, but occurs quite unexpectedly, very abruptly, and rather drenching.
• Prediction:
  • There is no satisfactory technique for anticipating the occurrence of cloud bursts through satellites and ground monitoring stations because they develop over a small area and for a period of time.
  • A very fine net work of radars is required to be able to detect the likelihood of a cloud burst and this would be expensive.
  • Only the areas likely to receive heavy rainfall can be identified on a short range scale. Much of the damage can be avoided by way of identifying the areas and the meteorological situations that favour the occurrence of cloud bursts.
• 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 Consequences of Cloudbursts?

• Flash floods: Flash floods are sudden, localised surges in water levels during or after intense rainfall.
  • Flash flooding starts within 6 or 3 hours of heavy rainfall. It is typically caused by intense thunderstorms 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 characterised 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.

What is the 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 destabilise 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 urbanisation can alter local climates and precipitation patterns, affecting microclimates in mountainous areas and potentially influencing cloudburst occurrences.

What are the 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.

  Drishti Mains Question: What are Cloudbursts and what are its mitigation strategies?

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