Understanding the Cloudburst Phenomenon in Himachal Pradesh

Cloudbursts: A Growing Concern in Himachal Pradesh

Pallavi Sharma
DHARAMSHALA:
In the hilly terrains of Himachal Pradesh, cloudbursts have emerged as a frequent natural disaster, leading to significant destruction and loss of life.

Among the state's twelve districts, five—Mandi, Shimla, Chamba, Kullu, and Sirmaur—are particularly susceptible to these extreme weather events. This heightened vulnerability stems from a complex interaction of geographical features, climatic conditions, and weather patterns.

What Causes Cloudbursts?

Cloudbursts are characterized by intense rainfall, where over 100 mm can fall within an hour in a localized area, often alongside thunderstorms. Research from IIT-Roorkee indicates that the majority of cloudbursts in Himachal are triggered by the rapid formation and subsequent collapse of cumulonimbus clouds, which are associated with thunderstorms.

The development of these clouds is primarily influenced by heat. During daylight, the sun heats the earth's surface quickly, especially in mountainous regions, causing warm, moist air to rise rapidly. As this air ascends, it cools and condenses, resulting in the formation of large cumulonimbus clouds.

When these clouds become trapped in specific areas due to geographical barriers like steep slopes, they can release a torrential downpour in a matter of minutes, a phenomenon referred to as a cloudburst. Rainfall during such events can range from 200 to 1,000 mm per hour, overwhelming the soil's ability to absorb water and leading to flash floods and landslides.

Why Are These Five Districts More Affected?

The IIT-Roorkee study, which analyzed cloudburst occurrences up to 2024, found that these five districts experience the highest rainfall during the monsoon season compared to other areas in the state. Their steep terrain, elevated altitude, and unique wind patterns create ideal conditions for the rapid formation of cumulonimbus clouds.

Researchers from NIT-Hamirpur corroborated these findings, noting that physical barriers like steep mountain slopes directly contribute to cloud formation. When moist air is forced to rise quickly due to these slopes, it accelerates the development of storm clouds, increasing the chances of sudden and intense rainfall.

In contrast, districts such as Una, Hamirpur, Bilaspur, Kangra, Kinnaur, Lahaul-Spiti, and Solan have less rugged landscapes or are situated in rain-shadow areas, resulting in significantly fewer cloudburst incidents.

Peak Season and Preparedness

Data indicates that July and August are the peak months for cloudbursts in Himachal Pradesh, with occurrences significantly higher than in June or September. This timeframe aligns with the main monsoon season, when atmospheric moisture levels peak and temperatures fluctuate rapidly due to sunshine and storm activity.

Given the increasing unpredictability of climate patterns, cloudbursts are expected to become more frequent and severe. Therefore, implementing early warning systems, enhancing drainage infrastructure, and establishing localized weather monitoring are essential to reduce risks to life and property in these vulnerable districts.

As the understanding of cloudbursts improves, it is crucial for policymakers and residents in Himachal's at-risk areas to stay vigilant and prepared, particularly during the peak monsoon months.