How climate change is making floods worse

Several regions in Bangladesh have been battered by catastrophic flooding over the past few days, killing at least 36 people and displacing hundreds of thousands. At least 17 of the country’s 64 districts, mostly in the north and northeastern Sylhet region, were affected by the natural disaster, with several areas also losing electricity.

Officials from Bangladesh’s Department of Disaster Management said that they were making “frantic efforts” to ensure there is food and drinking water for all the affected people. But some have complained that the government’s response has been slow and inadequate. “People in the remote places are getting nothing,” Nafisa Anjum Khan, a volunteer from Dhaka who is now working in the Sylhet and Sunamganj areas, told DW.

“For the seven days I have been working in those areas, I haven’t seen local officials put any effort to deliver aid to those areas,” Khan added. She said most of the groups working there were supplying dry food, which is not enough. “People are craving cooked food. And baby food is widely missing.” The UN children’s agency, UNICEF, said it was urgently seeking $2.5 million to respond to the emergency in Bangladesh and that it was working with the government to supply water purification tablets, emergency medical supplies and water containers. Bangladesh is considered one of the world’s most climate-vulnerable countries, and the poor are disproportionately impacted by the effects of such disasters.

The current crisis has been worsened by rainwater flowing down from the surrounding hills of India’s Meghalaya state, including some of the world’s wettest areas like Mawsynram and Cherrapunji, which each received more than 970 millimetres (38 inches) of rain on Sunday, according to government data.

G M Tarekul Islam, a professor at the Bangladesh University of Engineering and Technology’s Institute of Water and Flood Management, said climate change is a factor behind the erratic and early rains that triggered the floods. “The erratic rainfall in India’s Cherrapunji and other areas is the main reason for this flood. Because of global warming, the climate has changed and so has the pattern of rainfall. Now we are observing more and more heavy rainfall,” he told DW. In its sixth assessment report published last August, the Intergovernmental Panel on Climate Change also noted the increasing frequency of heavy precipitation events since the 1950s and connected them to human-induced climate change.

What other factors are behind the increased severity? Although floods are not new to the region, Islam said the changing climate has made the monsoon — a seasonable change in weather usually associated with strong rains — more variable over the past decades, resulting in longer dry spells interspersed with heavy rain.

“Because of global warming, more and more aqueous vapour accumulates in the sky as clouds. When precipitation begins, it also takes down the accumulated vapour with it. Thus, the rain becomes more erratic and heavier,” he explained. “That means, instead of getting an average amount of rain throughout the monsoon time, we get short spells of torrential rains.” The expert also blamed other factors like increased mining activity and deforestation on the Indian side for contributing to the increased severity of the floods.

“When stones are mined and trees are cut off, the downward run of water becomes much faster. So we see the water flowing down faster and the rivers getting inundated,” Islam said. “This also changes the river morphology. The extra sediments that are brought by the running water pile up on the riverbeds and further expedite the inundation.”