#Title Dhaka has long expanded faster than it has planned. Wetlands have been filled, low-lying areas built over, and high-rises have been raised that may not withstand a major earthquake. In the first instalment of a six-part series, Star examines the city’s fragile ground, soil liquefaction, and construction gaps that could turn a powerful tremor into a disaster. A city standing on fragile ground Over half of Dhaka lies in high liquefaction zones, raising risk of severe damage in major earthquake

HELEMUL ALAM

Residents across large parts of Dhaka face serious risks during a major earthquake, as much of the city stands on hazardous, liquefaction-prone soil, experts have warned.

They called for strict compliance with the Bangladesh National Building Code (BNBC), particularly proper piling and soil improvement, before buildings are constructed in high-risk areas.

A recent study by Rajuk and Buet shows that about 55-60 percent of Dhaka falls within the red and magenta zones of the city’s liquefaction hazard map, indicating highly vulnerable soil conditions.

“These areas also face high seismic amplification, as both hazards are linked to loose or artificially filled ground,” said Prof Mehedi Ahmed Ansary of Civil Engineering at Buet.

Within the 1,528 square kilometres under Rajuk’s jurisdiction, Buet researchers found that more than half the area is highly susceptible to soil liquefaction during a major earthquake.

Geologists said Dhaka’s soil profile, mainly red Pleistocene clay and soft alluvial deposits, is not suited to the city’s dense and largely unplanned expansion. A strong earthquake could therefore cause widespread structural failure.

Experts recommended proper piling and soil improvement, especially within the top five to six metres, in high-risk areas.

Buet classified Dhaka’s ground conditions into four colour-coded zones using the Liquefaction Potential Index. Red, with an LPI above 15, indicates the highest risk; magenta, with 10–15, indicates moderate to high risk; blue, with 5–10, indicates lower risk; and green, below 5, indicates the lowest risk.

Prof Ansary said red-zone areas could suffer severe ground failure during a magnitude 7.5 earthquake, particularly where groundwater levels are high, such as areas near ponds, canals and rivers.

Explaining seismic “Sandy

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