Landslide a natural phenomenon which is defined as the outward and downward movement of slope forming materials along the definite plane of failure under the influence of gravity. Landslide is recognized as the associated disaster with major events such as storm and earthquake but acts as the major disaster event in the context of Nepal.
Nepal is highly vulnerable to landslide because of its steep mountainous train, weak geographical formation along with steep topography in a hilly region, overgrazing of protective slope cover high-intensity rainfalls during monsoon. The rapidly increasing construction of infrastructures, such as roads, irrigation canals, and dams without due consideration given to natural hazards, is contributing considerably to triggering of landslides. Road failures as a result of rains and floods add enormous load to the stream and rivers which ultimately damage the infrastructures, settlements and cultivated land on the low lying area in Nepal.
Landslide usually occurs at steep slopes, they also occur in some places like cutting failures (excavation, construction) river bank failures, lateral spreading of soil material collapse of waste piles, garbage fills etc.
The main cause of the landslide is sudden shocks like earthquakes, hurricanes, volcanic eruptions, the passage of heavy trucks, blasting, and others may trigger the sudden mass movement of the soil in slopes. Besides this there are many others causes i.e. manmade factors (Constructions done without proper engineering inputs, farming practices, creation of new site conditions such as changes to natural slope due to construction activities, removal of vegetation cover and deforestation, etc.) and Natural factors (rapid snowmelt in mountains- rapid melting of snow adds water to soil mass on slopes, lowering of the water levels in rivers, reservoirs, etc. Weakness in the composition, material or geological structure of rock or soil formation, external factors, which impact the groundwater regimes. Examples are Heavy rain, snowmelt, changes in groundwater level etc, decomposition of rocks)
Talking about recent landslides occur in Nepal are unbelievable. 24 landslides were seen in last 14days where 20 people lost there lives. Coming to the total number of landslides of 2020 its 450 cases, death toll rises to 269, 69 people are still missing.
Source: Nepal Disaster Risk Reduction Protocol.
We can obviously see from above data that Nepal is highly vulnerable to a landslide but this doesn’t mean that mitigation, prevention and control worked cant be deployed. Natural phenomenons can’t be controlled but a better understanding of this phenomenon and its consequences could help us control the extent of the damage.
In order to control the slide following actions could be taken immediately.
• Reinforcement of floor slabs and external walls in existing buildings
• Protective forests plantation program
• Big check dam at the toe of the slide
• A series of check dams along the gullies.
• Supporting structure such as anchors and piles
• Horizontal drainage borings.
• Slope treatment control works
• Surface erosion control works
• Bio-engineering works
• Vegetation over the peripheral land.
Nepal is suffering from the problem of landslides causing a huge loss of economy, human lives and environment adversely. To minimize the effects of landslides and related mass movements in the future, it is necessary to identify and study the hazardous areas of the country. Proper understanding of the natural phenomenon and their impacts is necessary.