More than 300 mm of rainfall in 48 hours caused flooding in Bangkok — Channel NewsAsia

In Bangkok, Thailand, nearly continuous downpours in late September overwhelmed the drainage system and caused flooding in various parts of the city. More than 300 mm of rain fell over 48 hours, from September 24 to 26, after which a state of emergency was declared in all 50 districts of the capital. According to a government estimate, the disaster affected about 329,000 households, or around 700,000 residents, Channel NewsAsia reports.

Water does not recede in low-lying areas

In the Lat Krabang district on Bangkok’s eastern outskirts, which is located in a low-lying area, the water level exceeded one metre at its peak. Two weeks after the downpours, some residential streets still remained flooded: residents had to travel to dry areas to buy groceries, while elderly people had to move around in rubber boots or use transport.

Residents of the district said flooding warnings arrived only after the water had begun to rise. They also linked the prolonged flooding to clogged drains, construction debris and insufficient water pumping.

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Drainage system not designed for such downpours

Experts explained that the main cause of the current flooding in Bangkok was extremely intense local rainfall, rather than large volumes of water flowing through the Chao Phraya River, as during the catastrophic flood of 2011. Repeated rains saturated catchment areas, water levels in canals rose, and high tides made it more difficult to drain water into the sea.

According to specialists, urban development has gradually occupied natural water-storage areas and drainage routes. Landscape architect Kotchakorn Voraakhom said Bangkok has lost about half of its estimated 3,000 canals and is increasingly dependent on pumps and concrete drainage infrastructure. A preliminary assessment by Rangsit University put flood losses in Thailand over four days at 25.3 billion baht, or about $780 million.

Specialists call for stronger preparedness

The Bangkok Metropolitan Administration said pumping stations and water gates were operating at full capacity, but water levels in the main canals remained high because of inflows from adjacent areas. Experts believe it would have been impossible to completely avoid flooding at such rainfall intensity, but more timely warnings, proper drainage maintenance, more accurate modelling of flood zones and coordinated water-resource management could have reduced the damage.