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Last week, torrential rainfall across Indonesia’s largest island, Sumatra, triggered flash floods and landslides, causing widespread destruction. Twenty people died earlier this week in four areas in North Sumatra province amid flash floods and landslides. On Thursday morning, another devastating landslide claimed seven more lives. This landslide struck the main access route between Medan, the provincial capital, and surrounding regions, burying vehicles – including a tourist bus – in mud, rocks and trees. More than 10 people were injured and rushed to the nearest hospital in Medan. Rescue efforts are continuing, with several vehicles still trapped in the debris. North Sumatra’s traffic director estimated it may take up to two days to evacuate those affected.
Flash floods and landslides are a frequent occurrence in Indonesia owing to seasonal rainfall from October to March, caused by the Asia-Australia monsoon circulation system. This phenomenon causes wind to blow from Asia to Australia, bringing increased water vapour and consequential rainfall to Indonesia. Teleconnections such as El Niño-Southern Oscillation can also influence rainfall patterns, with the likely upcoming La Niña phase expected to bring further extreme weather by the end of the year, intensifying the risk of flooding and landslides as sea surface temperatures in the Pacific Ocean drop below average and easterly trade winds strengthen, pushing additional moisture into the region.
Over the past couple of days, there has also been flash flooding across Malaysia and Thailand, caused by heavy rainfall as a result of the monsoon. Between Wednesday and Thursday this week, the southern region of Thailand and northern parts of peninsular Malaysia received more than 90mm (3.5in) of rain, with other nearby areas recording more than 50mm.
As of Thursday, more than 50,000 people have been displaced in Malaysia, with the states of Kelantan and Terengganu being the most severely affected. In Thailand, more than 135,000 households have been affected by the flooding. Authorities in both countries are actively providing disaster relief and conducting urgent evacuations. The Asean Specialised Meteorological Centre has warned that the region can expect further heavy rainfall over the coming weeks, raising concerns for further flooding and disruption.
Furthermore, this week, a tropical depression in the south-west Bay of Bengal has brought strong winds, intense rainfall, and widespread flooding to Sri Lanka. As of Wednesday, more that 100mm of rain fell in just 24 hours. The storm has claimed 12 lives, left six children missing, and forced more than 250,000 people to evacuate their homes. The India Meteorological Department has warned that the depression could intensify into a tropical storm and reach the country by the weekend.