Nepal experienced incessant rainfall from August 11 to 14, 2017, resulting in widespread floods across 35 of the country’s 77 districts.1 Several districts experienced the heaviest rainfall in over 60 years. This led to the inundation of about 80 percent of the land in substantial parts of the Terai region.
Floods have historically resulted from a combination of the following natural factors in Nepal: continuous rainfall and cloudbursts, snowmelt and rainfall, glacial lake outburst floods and bishyari (breaking of dams caused by landslides falling directly into rivers). This year’s heavy rains were a result of the monsoon trough, an elongated area of low pressure that formed parallel to the foothills of the Himalayas; presence of low-pressure and the entry of moisture from the Bay of Bengal that released significant rains on the southern parts of the Chure range and the mid-hills. Shifting of the monsoon trough closer and away from Nepal is a common phenomenon. However, this year it extended from the east to the west of the country, causing heavy rains.
The monsoon is both a productive and hazardous resource in Nepal. When it brings the right amount of rain, agriculture productivity soars; when there is excess, it causes tremendous loss of life and property. During monsoon cloudbursts, landslides and flash floods occur in the mountains. In the southern plains, the same water breaches river banks and inundates swathes of land. The impact is aggravated by rapid urbanization in the Terai: physical construction along the embankments have interfered with the existing patterns of surface water flow and caused drainage congestion. With local hydrology changed, there has been flooding even in regions with no past experience of such calamities.
The booming construction industry has also driven up the demand for sand and gravel, usually mined from upstream river beds in the dry season. During the monsoon, the loosened sediments are transported downstream, which elevate the beds of river, causing them to meander and flood.
The 2017 flood spanned the entire breadth of the country. A total of 35 districts were affected of which 18 of them severely (see Figure 1). More than 190,000 houses were destroyed or partially damaged, displacing tens of thousands of people and rendering many homeless. Household assets and food grains were damaged and the affected communities faced shortage of food, water and non-food items. Many suffered infections from contaminated water.
In comparison to the past floods in 2001 and 2008, which killed 1,673 people, the 2017 floods saw reduced mortality and injuries. The number of people who died in the 18 most affected districts was 134 of which 44 were female. The districts where most of the deaths occurred are as follows: Rautahat, Morang, Jhapa and Sarlahi. The number of recorded injuries caused by the floods this year was only 22. In the severely affected 18 districts, the floods affected a total of around 1.7 million people (866,993 male and 821,480 female).