DEHRADUN: The recent disaster in Nepal has once again heightened concerns regarding the climate change and its derivative effect on glaciers and flash floods in the Himalayan region.
Manish Mehta, a scientist at the Wadia Institute of Himalayan Geology, who has studied the causes of disasters like those at Kedarnath, Rishiganga and Dharali in Uttarakhand, says the changes occurring in the Himalayas cannot be viewed merely as isolated incidents.
According to Mehta, rising temperatures are causing many Himalayan glaciers to steadily recede-a phenomenon known as "glacial retreat."
While an advancing glacier carries rocks, soil, and debris along with it, a retreating glacier leaves behind vast quantities of loose debris.
This debris lacks stability and can easily slide downslope during heavy rainfall or rapid snowmelt.
Scientists are also deeply concerned about shifting precipitation patterns-specifically the changes in rainfall and snowfall-in high-altitude areas.
Regions that previously experienced snowfall predominantly are now witnessing an increase in rainfall events.
This indicates that the snowfall zone is gradually receding to higher altitudes, while rainfall is extending to greater elevations.
Mehta explains that if high-altitude areas experience intense rainfall over a short period, the accumulated loose debris can become saturated with water and suddenly slide downwards.
This can trigger landslides or rapid debris flows.
At times, snow or debris at high altitudes obstructs water flow, creating conditions akin to a temporary dam.
When this barrier breaks, vast quantities of water, rocks, and soil rush downwards at high speed.
This is why many flash floods in the mountains do not consist solely of water; they also carry rocks, soil, and large amounts of debris.
The force of such debris-laden flows is far greater than that of ordinary floods, and they can cause massive damage to buildings, roads, and bridges in their path.
According to Mehta, incidents like those in Kedarnath, Dharali and Nepal must be understood in the context of the sweeping changes occurring in the Himalayas.
However, the cause of each disaster may differ, and the precise reason for any specific event can only be determined through scientific investigation.
He notes that landslides and debris flows are nothing new to the Himalayas.
As the Himalayas are a geologically young and active mountain range, such natural phenomena have been occurring there for millennia.
Yet, climate change now threatens to exacerbate the risks associated with these events.
Another shift is being observed in nighttime temperatures.
Previously, there was a significant difference between daytime and nighttime temperatures in high-altitude regions.
The drop in temperature at night used to slow the rate of snowmelt; however, minimum temperatures are now rising in many areas.
Consequently, the melting of snow and glaciers can continue even during the night.
According to Mehta, global warming alone cannot be held responsible for the escalating risks in the Himalayas.
Factors such as glacial retreat, shifting rainfall and snowfall patterns, extreme precipitation, rising nighttime temperatures, loose glacial debris, and steep mountain slopes-all these elements combined can intensify the severity of a disaster.
In this context, the recent incident in Nepal once again underscores the necessity for continuous monitoring and scientific study of the changes unfolding in the Himalayas, as even minor natural disturbances can sometimes escalate into major disasters for the settlements located downstream.
