Sciency Thoughts: Two dead and at least twenty eight missing as floods and landslides hit eastern Nepal.

Sunday 18 June 2023

Two dead and at least twenty eight missing as floods and landslides hit eastern Nepal.

One person is known to have died, and at least twenty five more are missing across eastern Nepal, amid floods and landslides associated with the arrival of this year's monsoon. In Sankhuwasabha District, eighteen workers at a hydropower project are missing after a flash flood swept seven houses in which they were staying into the River Hewa. A single body has since been recovered from the river, believed to be that of one of the missing workers, but has yet to be identified. In Panchthar District at least five people are missing after a flood, and in Taplejung District one person has died and three people are missing, all believed to be members of the same family, after a landslide hit their house.

Flood damage at Hewa Khola in Sankhuwasabha District, where eighteen people were swept away by a flash flood. Online Khabar.

The first clouds associated with the monsoon were spotted on Wednesday 14 June 2023, taking several days to spread across the country. All of the flooding incidents have been reported since the evening of Saturday 17 June, though they are unlikely to be the last. The National Disaster Risk Reduction and Management Authority is predicting lower rainfall this year than in recent years, combined with higher temperatures, but is still expecting about 1.25 million Nepalese citizens will be affected by incidents relating to the monsoon this year (for comparison, about 2 million were affected last year.

Monsoons are tropical sea breezes triggered by heating of the land during the warmer part of the year (summer). Both the land and sea are warmed by the Sun, but the land has a lower ability to absorb heat, radiating it back so that the air above landmasses becomes significantly warmer than that over the sea, causing the air above the land to rise and drawing in water from over the sea; since this has also been warmed it carries a high evaporated water content, and brings with it heavy rainfall. In the tropical dry season, the situation is reversed, as the air over the land cools more rapidly with the seasons, leading to warmer air over the sea, and thus breezes moving from the shore to the sea (where air is rising more rapidly) and a drying of the climate. This situation is particularly intense in South Asia, due to the presence of the Himalayas. High mountain ranges tend to force winds hitting them upwards, which amplifies the South Asian Summer Monsoon, with higher winds leading to more upward air movement, thus drawing in further air from the sea.