Located in the central of the Himalaya range, Nepal is one of the most disaster prone countries in the world due to its topography and climatic condition. Earthquakes, landslides, floods, fire, thunderbolts are the major causes of disaster events that caused major damaged in the past, weakening the fragile ecosystem of the country. Economic Vulnerability Analysis shows that Nepal exhibits the largest losses due to large exposure at risk and the high level of hazards. As a matter of these phenomena not only cause loss of lives and properties, but also pose severe threats to physical infrastructure, and also disrupt economic development. The frequently occurring natural disasters and likely zones are given below.
Landslide is one of the very common natural hazards in the hilly region of Nepal. Both natural and human factors such as steep slopes, fragile geology, high intensity of rainfall, deforestation, unplanned human settlements are the major causes of landslide. The risk of landslide is further exacerbated by anthropogenic activities like improper land use, encroachment into vulnerable land slopes and unplanned development activities such as construction of roads and irrigation canals without proper protection measures in the vulnerable mountain belt. The hilly districts of Nepal located in the Siwalik, Mahabharat range, Mid-land, and also fore and higher Himalayas are more susceptible to landslide because of steep topography and fragile ecosystem.
Flood is a common cause of flood in the rainy season in Nepal, and has been most frequent, highly damaging and wide spread natural hazards. It is estimated that more than 6,000 rivers and rivulets are in Nepal flowing from north to south. Among these, snow fed rivers, such as the Koshi, Narayani, Karnali, and Mahakali, are perennial rivers. They originate from the Himalayas and snow capped mountains and pass through the hills to the Terai plains. During the monsoon (June-September), these rivers swell and cause damage to the villages, crops lands, and people and livestock remained within the river basins. Historical data has shown that Nepal witnessed major flood in Tinao basin (1978), Koshi River (1980), Tadi River Basin (1985), Sunkoshi Basin (1987) and devastating cloud burst in Kulekhani area (1993) which alone claimed the lives of 1336 people.
Gacial Lake Outburst Floods (GLOFs)
Glacial lakes are located in the high altitude areas particularly in the foot hill of mountain. The lakes are formed due to damming in by moraines. These lakes contained huge volumes of water melting of glacier may lead to outbreak the lakes, called a glacial lake outburst flood (GLOF) with substantial capacity to cause great damage in downstream. 2,315 glacial lakes have, in total, been identified in Nepal and 14 GLOFs were recorded to have occurred between 1935 and 1991 in Nepal. At this background, 15 glacial lakes are found substantially dangerous in Nepal.
Nepal on a regular interval witnesses earthquake along the major active faults in east-west alignment. Historical data and ongoing seismological studies have clearly indicated that the entire region of Nepal is prone to earthquake and it lies in the active seismic zone V. It is evident that the seismic pattern has geographically divided into three clusters of events; viz: western, central and eastern Nepal. It has also pointed out that Siwalik, lesser Himalaya and frontal part of the Higher Himalaya are the most vulnerable zones. Historical data has shown that the country witnessed three major earthquakes in 20th century namely Bihar-Nepal earthquake (1934), Bajhang earthquake (1980) and Udayapur earthquake (1988). According to Global Report on Disaster Risk, Nepal ranks the 11th position in terms of earthquake risk as earthquakes have often occurred in Nepal.
Of the total households of the country, nearly 78 percent house holds are agro-base households. In the rural areas thus, about 86 percent of the population lives in the houses made of earthen wire, stone and wood. In Nepal, houses for residential purpose are developed in cluster basis which are more susceptible to catching fire and spreading over there immediately due to close connectivity especially in the dry season. Wildfire is another cause of natural disaster which usually occurs during dry season, especially in the mid hill areas. In the Terai region, fire, including the wildfire occurs mainly in the dry season.
Drought is the frequently happening hazard in Nepal. This is mainly caused by uneven and irregular low monsoon rainfall. Some parts of Terai, mid-land and Trans-Himalayan belts of Nepal are prone to drought. The lack of irrigation facilities further exacerbates the effect of drought causing enormous loss of crops production leading to the shortage and insecurity food. The droughts happened in 1972 and 1979 were the most seriously damaging and harmful to the people, livestock and crops. In 1994 Nepal witnessed the worst drought in its history that affected 35 districts of western hilly and Terai regions.
Avalanches are a rapid movement of snow and debris flowing down through the slope or flanks of mountains. It can be triggered by natural factors like slopes, thickness of snow or human activity. They have the capacity to carry massive masses of snow and associated debris that make them one of the most destructive elements of hazards. The high mountainous region having the rugged and steep slopes topographically is susceptible to avalanche. A number of cases of avalanche with destructive nature have been reported in Nepal. Unexpected Seti River Flood of 5th may, 2012 at Kaski district could an example of this type of hazard.