A sudden cloudburst, an aggressive rainstorm occurring most often in mountainous regions, had occurred for a short period in the region where the terrain was already weak, which caused the disaster, said Rishi Ram Sharma, director general at the Department of Hydrology and Meteorology (DHM), on Thursday.  

According to the Meteorological Forecasting Division (MFD), the hydrological and meteorological station based in Taplejung recorded rainfall measuring 129 millimetres, highest among all the 19 meteorological stations within 24-hours period, between 8:45 am on Wednesday and 8:45 am on Thursday.

Meteorologists term rainfall measuring greater than 100 millimetres in 24 hours period as extreme precipitation event, one of the severe weather hazards that could pose serious threats to lives and properties.

The earthquakes on April 25 and May 12 followed by numerous aftershocks have caused slope fracturing and weakening of rock mass in 14 most affected districts.

The cracks, fissures and slides on the land surface and hill slopes are highly vulnerable to landslides, especially during monsoon.  

Taplejung was not in the list of most affected districts from the recent earthquakes, though tremors including the 6.8 magnitude earthquake that struck Sikkim in India in 2011 had badly affected the district.

The monsoon has not even started, and it is very unusual that rains that fell for a short period of time could cause a massive runoff and landslip, unless the slope failure or weathering already existed in that area, said Madhukar Upadhyay, a hydrologist and watershed management expert.

The Taplejung landslide is also a remainder of our poor preparedness to deal with

the regular landslides as well as the earthquake-triggered landslides that are expected to become more frequent and severe in the coming days.

Normally landslides occur after continuous rains for days when the surface is wet and runoff takes place. “This deadly landslide in Taplejung could just be the trailer

of what we might see in the

next 3-4 months in the country where majority of the hill

and mountain slopes are unstable and weakened due to earthquakes and frequent aftershocks,” Upadhyay said.

“It also brings the reality of poor understanding of our own mountain configuration, changes that has taken place in mountains due to unplanned land use and development activities in the recent years.”

MFD has stated that the onset of monsoon is expected within next two days, a delay of couple of days than the usual onset date of June 10.

 “The existing weather condition is becoming favourable for monsoon onset in the eastern region as thunder and lightning along with brief showers are expected,” said MFD.

The weather update posted on Thursday by MFD further mentioned that even intermittent rainfall can trigger

landslides in earthquake-affected region while urging

the people to stay prepared and safe.

“With monsoon already around the corner, the most possible alternative to minimise the risks of landslides is by monitoring the changes in the slides, gaps and slope surface that are hit by the earthquakes and also those regular landslide areas,” Upadhyay said.