It has been reaffirmed that increased human-led activities resulted in formation of sinkholes in Armala village in Pokhara Valley recently.

River encroachment, illegal stone mining led to the deepening of Kali Khola that flows on both sides of the village. Similarly, water eroded clayey silt and upper layer of the soil collapsed forming sinkholes, according a latest research on land subsidence problem in the village.

The research findings have supplemented the claims of experts and other concerned authorities that the increased unplanned human activities led to the environmental disaster in the area.

According to Basanta Raj Adhikari, associate professor at the Department of Civil Engineering in Pulchowk Campus, who was involved in the research work, 12.8 liters of water per second is flowing from the hole and one fourth of the total sediment flowing is kaoline—a soft clay material found on the earth’s surface.

It has also been found that the area where the village is situated was a marginal lake during the formation process of the Pokhara valley and the clayey silt was deposited during the lake formation.

The interface of phyllitic rocks (that consist of fine grained sheet of weak silicate materials) and sediment deposit led to the formation of kaoline structure making the area vulnerable to seepage of water underneath the surface. In the last week of November, sinkholes measuring up to 5 feet deep and 5.5 feet in diameter started forming in the village threatening the lives of hundreds of people living in the area. It is estimated that more than 40 sinkholes appeared in the village and the process of formation continued for more than three weeks.

“There is a need to stop sand and stone mining in the Kali Khola area and conduct detailed sub-surface investigation by using electrical resistivity tomography,” Adhikari said.