Cloudburst

Free PDF's 5th August 2023

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Introduction

A cloudburst is a localised but intense rainfall activity.
Short spells of very heavy rainfall over a small geographical area can cause widespread destruction, especially in hilly regions where this phenomenon is the most common.
Not all instances of very heavy rainfall, however, are cloudbursts.
A cloudburst has a very specific definition:

Rainfall of 10 cm or more in an hour over a roughly 10 km x 10-km area is classified as a cloudburst event.
By this definition, 5 cm of rainfall in a half-hour period over the same area would also be categorized as a cloudburst.

Cloudbursts in India: Characteristics and Regional Occurrence

According to the IMD, 100mm of rain in an hour is called a cloudburst.
They usually occur over a small geographical region of about 20 to 30 sq. km.
Tall, cumulonimbus clouds causing cloudbursts can occur very quickly, in about 30 minutes.
In India, cloudbursts often occur during the monsoon season.
They occur mostly over the Himalayas, the Western Ghats, and the northeastern hill States of India.

Detection Challenges

Cloudbursts' small geographic coverage (around 20 to 30 sq. km) makes them difficult for satellites to detect due to their limited resolution.
Ground-based monitoring stations also struggle to capture cloudburst characteristics due to their localized and brief occurrence.
The use of multiple weather radars can provide timely updates, but the high cost of implementation remains a challenge.

Impact of Climate Change

Climate change is anticipated to increase both the frequency and intensity of cloudbursts.
The observed changes in monsoon extremes and cloudburst occurrences are linked to the rise of 1 degree Celsius in global surface temperature.
Projections indicate further temperature increases of 1.5°C during 2020-2040 and 2°C during 2040-2060, potentially exacerbating cloudburst events.

Changing Rainfall Patterns and the Intensification of Extreme Weather Events

Absence of Long-term Trend in Cloudbursts: The IMD-defined cloudbursts do not exhibit a significant long-term trend in terms of occurrence. Cloudbursts, as specific events, may not show a consistent rise over time.

Rising Incidents of Extreme Rainfall: Globally, extreme rainfall events are increasing, including in India. The overall amount of rainfall in India has not experienced substantial changes. However, a higher proportion of rainfall is concentrated within shorter time periods.

Intensification of Wet Spells: Wet spells are becoming more intense, characterized by heavy downpours and high precipitation rates. These intense rain events contribute to the occurrence of cloudburst-like conditions in localized areas.

Prolonged Dry Spells: Concurrently, prolonged dry spells are observed, even during the rainy season. These periods of reduced rainfall exacerbate the impact of intense rain events and further affect water availability.

Kedarnath flash floods (2013):

The Kedarnath flash floods, triggered by a cloud burst, represent one of the most catastrophic natural disasters in recent Indian history.
On June 16-17, 2013, a cloud burst and subsequent flash floods occurred in Kedarnath, Uttarakhand, India.
Intense rainfall led to flash floods, landslides, and overflowing rivers.
The event resulted in extensive loss of life, damage to infrastructure, and displacement of residents and tourists.
Response and recovery efforts included rescue operations, relief operations, and long-term reconstruction and rehabilitation.

The disaster highlighted the importance of early warning systems, disaster preparedness, and sustainable development practices.

NDMA Guidelines for Cloudbursts:

Early warning systems: Setting up early warning systems such as rain gauges, and weather monitoring systems, and dissemination of timely warnings to the public through various media platforms.
Floodplain zoning: Zoning of floodplains to restrict construction and minimize damage to human settlements and infrastructure.
Improved land-use practices: Adopting improved land-use practices such as soil conservation, afforestation, and rainwater harvesting, can reduce runoff and reduce the risk of flash floods.
Strengthening of infrastructure: Strengthening of infrastructure such as roads, bridges, and water supply systems to ensure their resilience to natural disasters.
Emergency response plans: Developing and regularly updating emergency response plans to ensure timely and effective response to disasters.
Community involvement: Involving communities in disaster risk reduction activities, such as creating evacuation plans, identifying safe locations, and preparing for disaster response.
Regular training and drills: Regular training and drills for disaster response teams, community volunteers, and the general public to improve their preparedness and response capabilities.

Way Forward

Improve urban infrastructure and stormwater drainage systems to handle high-intensity rainfall.
Increase the capacity of drainage networks and ensure regular maintenance to prevent blockages and overflow.

Promote nature-based solutions, such as rainwater harvesting and the use of green spaces, to absorb and manage excess rainfall.
Encourage sustainable urban planning practices that integrate green infrastructure and water-sensitive designs.

Conduct awareness campaigns to educate communities about cloudburst risks and appropriate response measures.
Enhance community preparedness through training programs and drills, ensuring that individuals are equipped to respond effectively.

Implement and enforce building codes that consider cloudburst risks, including the construction of flood-resistant structures and appropriate site selection.
Encourage retrofitting of existing buildings to withstand cloudburst impacts.

Invest in research and development to improve understanding of cloudbursts and develop innovative technologies for early detection and effective management.
Foster collaboration between scientific institutions, government agencies, and other stakeholders to address cloudburst-related challenges.

Assistance for States:

In March 2023, the High-Level Committee (HLC) under the Chairmanship of the Union Home Minister approved the additional Central assistance under the National Disaster Response Fund (NDRF) to five States, which were affected by flood, landslides, cloudburst during 2022.

Conclusion

Cloudbursts are an emerging concern due to their unpredictable nature and severe impact on localized areas.
With climate change driving alterations in monsoon patterns and increasing the likelihood of extreme events like cloudbursts, it becomes essential to enhance monitoring and early warning systems.
Effective mitigation measures and adaptation strategies are crucial to mitigate the risks posed by cloudbursts and their impacts on vulnerable regions in India.