Every year during the monsoon, Nepal suffers heavy loss of life and property in rainfall-related disasters. Natural as well as human activities are responsible for floods and landslides at this time.
Nepal is situated on the lap of the Himalayas, which are young, tectonically-active mountains with fragile geology. This geographical placement makes the country susceptible to landslides and erosion. Natural erosion process, pore water pressure, and geological conditions are the major drivers of landslides. Moreover, repeated earthquakes have destabilized the rock mass and loosened the soil of the mountains, further increasing the risk.
Add to this, the haphazard construction of roads and settlements on hills and mountains, and you have a recipe for disaster.
Erratic weather patterns, often attributed to climate change, have also increased the number of rain-related disasters.
Early start and late withdrawal of the monsoon has become common in recent years, which scientists and meteorologists ascribe to climate change.
Pre- and post-monsoon periods in Nepal are seeing more than average amounts of rainfall.
On average, Nepal receives more than 80 percent of the total rain during the monsoon season (June-Sept) alone. The normal onset of the monsoon is June 13 while the withdrawal date is Oct 2–or after 112 days.
Ideally, 1,470mm of rainfall during these four months is considered normal. But this year, meteorologists say, the monsoon arrived on June 5, eight days earlier than its normal date. The Department of Hydrology and Meteorology has forecast heavier-than-usual rainfall.
Compared to the normal, the duration of the monsoon was longer last year and the year before as well.
The rainy season lasted for 126 days in 2020; it was 122 days in 2021. The longest monsoon in the past 25 years was recorded in 2008, at 129 days. Nepal received 1,558.4mm rainfall in that monsoon. The wettest monsoon, however, was 1998 when the country received 1,806.7mm rainfall.
In 2006, monsoon arrived almost 11 days earlier on June 1 but ceased on Sept 29, much sooner than the normal withdrawal date. The shortest monsoon was in 2002 when the season concluded on Sept 19. Still, the country that year saw 1,463mm rainfall (seasonal normal).
As weather gets more and more unpredictable, it is getting difficult to plan and implement effective disaster reduction responses.
Meanwhile, lack of preparedness and resources has added to Nepal’s vulnerability to rain-related disasters.
Monsoon comes with both positives and negatives
Sanot Adhikari, Environment expert
There is no way to specify exact monsoon dates. If the calculation is off by a few days, it is considered normal. However, things could go wrong if the onset date is almost a week earlier. This is regarded as an untimely start of the monsoon, and it could invite many rain-related disasters.
Intensity, amount, and precipitation patterns also determine the consequences of the monsoon. For example, the onset date this year is the earliest in a decade. This could invite natural disasters like floods, landslides, and soil erosion. But if there is normal intensity and amount of rainfall and if the withdrawal date also came earlier, the damage will be limited. Rather, it will help with farming and irrigation.
However, the Department of Hydrology and Meteorology predicts that there will be more rainfall this season. Last year, the monsoon didn’t start too soon; yet, due to heavy rainfall (intensity) at the start of the season, there were devastating floods in Melamchi and other rivers.
