Bangladesh’s worst flooding in more than a century has so far killed dozens and displaced nearly 4 million, with authorities warning that water levels will remain dangerously high in the north this week.
Experts say the catastrophic rain-triggered floods, which submerged much of the country’s northern and northeastern regions, are the result of climate change.
Bangladesh, a densely populated delta nation, is also one of the most climate-vulnerable countries in the world, where the poor are disproportionately affected as frequent floods threaten livelihoods, agriculture, infrastructure and drinking water supply.
A 2015 study by the World Bank Institute indicated that around 3.5 million of Bangladesh’s 160 million people are at risk of flooding each year.
Saiful Islam, director of the Institute of Water and Flood Management (IWFM) at Bangladesh University of Engineering and Technology (BUET), analyzed 35 years of flood data and found that rains were becoming increasingly unpredictable and many rivers were rising above dangerous levels. frequently than before.
“The last seven years alone have brought five major floods, eroding people’s ability to adapt, especially in the northern and northeastern parts of the country,” Islam told Al Jazeera.
Quoting from one of his research papers, he said that although average global temperatures increased slightly – by 2 degrees Celsius (3.6 Fahrenheit) above the pre-industrial era average – flooding along the basin Brahmaputra in northeast India and Bangladesh are expected to increase by 24 percent.
With an increase of 4 Celsius (7.2 F), flooding is expected to increase by more than 60%, according to Islam’s research.
Several rivers, including the Brahmaputra, one of the largest in Asia, flow downstream from northeast India through the low-lying wetlands of Bangladesh when they empty into the Bay of Bengal.
However, this year, excess rainwater from the Indian states of Assam and Meghalaya that pours into the Meghna and Jamuna rivers in Bangladesh could not drain because the wetlands were already saturated by a pre-monsoon flooding last month.
“Siltation of riverbeds caused by deforestation and dumping of solid waste has already reduced the water carrying capacity of rivers in Bangladesh,” IWFM researcher Ashiq Iqbal told Al Jazeera.
“Furthermore, the excessive extraction of sand and stone upstream from India has loosened the soil, which eventually ends up at the bottom of the river and decreases navigability. As a result, the entire systems become clogged. And this clogged system lost its ability to drain water from two quick successive floods in a short time,” he said.
Unplanned construction along the northeast wetland is another reason the rivers have become clogged arteries, said Mominul Haque Sarkar, senior adviser at the Center for Environment and Geographic Information Services ( CEGIS), at Al Jazeera.
“Many pocket roads as well as culverts are being built at different locations in the wetland. As a result, the water flow is obstructed and it swells when it rains excessively,” Sarkar said.
Most towns and villages in northern Bangladesh do not have protective dams. So when the water level in wetlands or rivers starts to rise, it quickly enters residential areas and floods them, he said.
To deal with floods, conventional methods such as building dykes along major rivers were proposed as part of a flood action plan implemented in 1990.
But some experts say structural measures to contain flooding are ineffective.
Mohamad Khalequzzaman, a geoscientist at the University of Lock Haven in the United States, told Al Jazeera that it is “difficult and undesirable to contain floods with fortified walls”.
“There may be a need to contain flooding in selected locations where there is a high concentration of people and resources, such as in major cities,” he said. “But in a geography dominated by wetlands, that’s not necessary.”
Khalequzzaman said delineating low-lying areas using permanent embankments, or polders, was a popular intervention in countries like Bangladesh. “Polders separate rivers from floodplains, which intensifies river flow and causes riverbank erosion,” he said.
He said the water resources of major rivers in Bangladesh should be managed by involving all co-riparian countries in the Ganges-Brahmaputra-Meghna (GBM) basins – Bangladesh, India and Bhutan.
“The problem is that only 8% of the GBM basins are located within the geographical territory of Bangladesh. So, in reality, without an integrated water resources pact between all WBG basin countries, floods cannot be properly managed in Bangladesh,” he said.
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