Ctg building itself into climate danger

ADB report shows construction in port city growing fastest in flood-prone zones

Nearly a quarter of Chattogram’s built-up area lies in places that would go underwater during a severe coastal flood, yet these are the areas where the city is expanding fastest, according to an Asian Development Bank (ADB) study.

The port city’s total settlement extent or built-up areas, meaning land covered by buildings, roads and other infrastructure, increased from 66.1 square kilometres in 2016 to 73.5 square kilometres in 2025, the ADB said in its Asia-Pacific Climate Report 2026, released yesterday.

Between 2016 and 2025, flood-prone settlement grew by 16.2 percent, compared with 9.7 percent of built-up areas on safer land, and 11.2 percent across the city as a whole.

Growth was fastest in areas where severe flooding could leave 0.5 to 1.5 metres of water, at 16.6 percent. In areas where floodwaters could exceed 1.5 metres, settlement grew by 16.1 percent.

Floodwater deeper than 0.5 metres can damage buildings and disrupt water supplies, sanitation and electricity, the report said.

“Chittagong stands out as the clearest warning, with growth concentrated in the deepest zones,” it said.

The report, which ADB describes as the first assessment of coastal risks across all 30 of its coastal developing member countries, draws on satellite records, flood modelling and household surveys.

It tracks settlement growth in five Asia-Pacific coastal cities: Shanghai, Manila, Chattogram, Hai Phong and Nuku’alofa in Tonga. 

In Manila, the most exposed areas grew the slowest, while in Hai Phong the fastest growth occurred outside the flood zone.

With much of Chattogram still undeveloped, the report says, planning decisions will substantially determine how exposed the city becomes, and the losses that follow.

Urban planner Delwar Hossain Mazumder, former chairman of the Chattogram centre of the Institution of Engineers, Bangladesh (IEB), said the findings reflected what was happening on the ground.

Safer areas were built up long ago, while port-related businesses and an influx of workers were driving construction onto cheaper, low-lying land that was once covered by water, he said.

“The Chattogram Development Authority (CDA) makes plans and considers its job done, without properly monitoring what is being built where,” he said.

With a new master plan nearing completion, he urged the authorities to strengthen the CDA, incorporate independent planners’ input and strictly enforce planning rules, allowing “not even a hair’s breadth of deviation”.

Otherwise, he warned, “the city will quickly become unliveable”.

He cited Kolkata, which he said had been heading towards becoming unliveable in the last century before authorities tightened planning controls and expanded the city into a new, planned area.

Asked whether flood risks were considered when approving buildings, CDA Deputy Chief Town Planner Abu Isa Ansari said the authority’s plan did not designate any part of Chattogram as flood-prone.

However, he said, the master plan prohibits construction in designated water-retention areas to help tackle waterlogging.

He attributed rapid construction in areas such as Bakalia and Chandgaon, which lie along natural drainage slopes between the city’s hills and the river, to the daily influx of people from surrounding upazilas.

“Had satellite towns been built in those upazilas, people would not have come. But Chattogram could not do that,” he said.

PORTS, POVERTY AT RISK

Beyond the city’s immediate flood threat, nearly all of Bangladesh’s ocean-related climate losses could stem from disruption at its ports, including the wider costs to trade, according to ADB research accompanying the report.

Chattogram port handles about 92 percent of the country’s import-export trade.

Under a high-emissions scenario, the value at risk could reach about $1.4 billion a year by 2050 and $13.6 billion by 2100, at 2020 prices.

Under the same scenario, around 1.75 crore Bangladeshis could be affected by coastal flooding annually by 2100, the third-highest figure among the 30 countries, after China and India.

Annual damage could reach about 15 percent of 2020 GDP by the end of the century.

Bangladesh also has the region’s sharpest overlap of poverty and flood risk, the report said.

The country’s poorest coastal communities are concentrated in the most flood-prone areas, leaving those with the greatest need for adaptation least able to afford it.

One study cited in the report found that Bangladeshi households spent 17.25 percent of their annual income on flood protection.

Meanwhile, dry-season groundwater in coastal areas routinely exceeds World Health Organization salinity limits. Saltier drinking water has also been linked to dangerously high blood pressure in pregnant women.

Citing a 2018 World Bank estimate, the report said sea-level rise, water scarcity and agricultural decline could force up to 13.3 million Bangladeshis, about 7.5 percent of the population, to move within the country by 2050.

The report praised the Bangladesh Delta Plan 2100 as one of the region’s most advanced but warned that financing it would be difficult.

The plan envisages $52 billion in investment through 2040, requiring delta-related spending of about 2.5 percent of GDP annually, against existing adaptation spending of around 0.8 percent. Some 99 percent of the funding must come from public sources.

Bangladesh’s cyclone shelter network, now numbering around 5,000, was cited as a success. Deaths fell from 1,38,866 in the 1991 cyclone to 111 in a comparable storm in 1997, the report noted.

[Chattogram Staff Correspondent Sifayet Ullah contributed to this report]