Risk of landslides irreversible in Himachal Pradesh, says consultancy

The intensity of landslides and their frequency in a hilly state such as Himachal Pradesh seems to make it inevitable the risk is irreversible, according to global disaster risk management firm RMSI. “It is crucial to have a relook at the structural configuration of buildings in the region, down to their very foundations,” says Pushpendra Johari, Senior Vice-President of the company. 

Vulnerable top soil

The series of events unfolding over the last weekend and into this week is proof of the devastation that landslides can inflict. “We must understand activities such as unchecked development, road construction by rock blasting, heavy traffic, and improper construction have weakened the connect between the top layer of the soil and the hard rock layer below. Landslides are triggered whenever heavy rains lash such vulnerable regions, leading to saturation of the top soil,” he told businessline. 

Top soil saturation caused by the incessant rains triggered by cloudbursts since last weekend, has had devastating results in Himachal Pradesh. Unrelenting rains on Saturday and Sunday sent soil saturation to its limits. Additional rains on Tuesday and Wednesday resulted in a series of slope failures, causing significant damage to property and loss of human life.

Also read: Heavy rain, landslides disrupt business and industrial activity in Himachal

Worst-hit districts

Solan, Shimla, Mandi, Hamirpur, and Kangra are amongst the worst hit districts. The state as a whole has experienced excessive damage to property and roads. Schools and colleges are shut, and over 800 people have been evacuated from the low-lying areas of Kangra. In Shimla, the national highway connecting Solan with the neighbouring areas, has emerged as a landslide hotspot. National highways and major roads in Mandi, too, are prone to landslides. Areas along the western border of the state, particularly around Dalhousie in Chamba, as well as roads on the higher Himalayas, are also hotspots for heavy rain and associated landslide risk.

170 cloud burst events

According to Johari, there have been 170 cloudbursts and landslides in this monsoon season, which have damaged at least 9,600 houses in the state. An estimated 800 roads remain blocked. The state has suffered a loss of around ₹10,000 crore, the Chief Minister said. Intensive rescue operations are underway in the Summer Hills and Krishna Nagar areas of Shimla, where huge landslides have taken place. 

Also read: Rain fury hits northern States; Himachal worst hit

RMSI analysed the daily mean rainfall for August versus the daily observed rainfall for Kangra, Mandi and Shimla over a 30-year (1990-2023) period. Table 1 shows the observed rainfall last week has large deviations from the daily 30-year mean rainfall. RMSI had its landslide forecast model active for Himachal Pradesh. Figure 1 depicts the landslide locations with high risk predicted by the model for Monday last. It overlays the approximate locations of a few major landslide events actually reported in recent days. The reported landslide sites overlap with the road stretches predicted to be under very high landslide risk. 

Observed vs normal rainfall for Kangra district | Photo Credit: RMSI

Observed vs normal rainfall for Mandi, Shimla districts | Photo Credit: RMSI

RMSI has also forecast landslide threat scenarios for Thursday. The predicted rainfall shows a decreasing trend as compared to the last few days. The loose soil columns on steep slopes were no longer as wet and saturated as observed on Monday, as there was much lesser rainfall on Tuesday and Thursday, Johari said. 

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