Saturday 12 March 2022

Landslide in Selangor State, Malaysia, kills four.

Four people have now been confirmed dead following a landslide that hit a row of houses at Bukit Permai in Selangor State, Malaysia, slightly before 6.00 pm local time on Thursday 10 March 2022. The incident happened following a heavy downpour associated with the onset of the onset of the Southwest Monsoon, and buried five houses along with a number of vehicles. Landslides are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall. The deceased have been identified as Mahendran Arumugam, 36, Ramasamy 58, Mohd Saiful Ridzuan, 33, and Chong Swee Kim, 84. Following the incident a hundred houses close to the site have been evacuated by local authorities until they have investigated the cause of the incident and confirmed it is safe to return.

Homes hit by a landslide in Selangor State, Malaysia, on Thursday 10 March 2022. Faihan Ghani/The Star.
Malaysia has two distinct Monsoon Seasons, with a Northeast Monsoon driven by winds from  the South China Sea that lasts from November to February and a Southwest Monsoon driven by winds from the southern Indian Ocean from March to October. Such a double Monsoon Season is common close to the equator, where the Sun is highest overhead around the equinoxes and lowest on the horizons around the solstices, making the solstices the coolest part of the year and the equinoxes the hottest.
The winds that drive the Northeast and Southwest Monsoons in Southeast Asia. Mynewshub.

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.
Diagrammatic representation of wind and rainfall patterns in a tropical monsoon climate. Geosciences/University of Arizona.
Malaysia has become increasingly landslip-prone in recent years due to extensive deforestation, which leaves soil exposed to heavy tropical rainfall. Concerns have also been raised about the large number of construction sites on steep hillslopes in urban areas, where workers are particularly vulnerable to landslip events during the Monsoon Seasons. Following the 10 March Bukit Permai landslide, local authorities investigating the incident are paying particular attention to any deforestation or soil extraction activities upslope of the affected area.
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