Climate data links devastating floods to record rains

Water is eroding the land of Chitri village of Nabinagar West union in Brahmanbaria as the mighty Meghna river continues to devour the agricultural lands and farms in the area. — Focus Bangla photo

Extreme rainfall over a wide region stretching from northeast Bangladesh to its adjacent upstream areas across the Indian border was the main cause of the recent floods, water resources and tourism experts said. climate, referring to climatic data.

An analysis of station-by-station rainfall data provided by the Flood Forecasting and Warning Center for June cumulative rainfall found that 10 of the stations saw their historic rainfall records broken with up to 40% excess rainfall.

There were 17 other stations, mostly in the Meghna basin of the northeastern haor region, where above-normal rainfall, up to 272% excess, was recorded, the analysis showed.

Overall, Sylhet Division recorded the highest June rainfall on record of 1,456mm this year since record keeping began in 1952, surpassing the previous highest rainfall record of 1,396mm measured in June 2004.

“We see yet another example of the strong correlation between extreme rainfall events and floods,” said senior meteorologist Sayeed Ahmed Chowdhury, recalling the devastating floods of 2004.

Large swaths of countryside in Sylhet division remained under water for 19 consecutive days until Monday, with more than 80,000 people still stranded in flood shelters.

Exactly 304mm, or more than 37% of normal rain for a month, was recorded one day in Sylhet on June 18, the Sylhet Met Office said.

The floods have affected millions of people in the northeastern and northern regions, mainly in Sylhet, destroying more than a million houses according to preliminary estimates and leaving 107 dead until Monday.

Dozens of people have also been killed in India due to landslides and flooding caused by extreme rainfall, with at least 15 stations in northeast India reporting severe or moderate flooding, mostly in India. Assam and Meghalaya, until Monday.

“We have evidence at hand that climate change is intensifying regional rainfall,” said Arifuzzaman Bhuyan, Executive Engineer, FFWC.

“This flooding was clearly a climate-induced natural disaster,” he added.

Nine of the 10 places where the historical rainfall record has been broken are in the Meghna Basin. These are Kanaighat, Sylhet, Chhatak, Latu, Sherpur, Lalakhal, Dakhinbagh, Lorergarh and Moheshkhola.

Sherpur in Sylhet experienced the biggest deviation in June rainfall recording 1,225mm of rainfall this year, 37% more than its previous record maximum rain of 895mm. The average normal rainfall for this station for the month is 514 mm.

The Dalia station in the Teesta basin also saw rainfall break all-time records.

Places with above-normal rainfall included 10 in the Meghna basin, four stations in the Brahmaputra basin, two in the Ganges basin and one in the southeastern hills basin, according to the climate record.

The highest above normal rainfall was recorded in Jaflong where 2219mm of rain was recorded in June against a normal average of 597.2mm.

The historical record represents meteorological data kept mainly for five decades since the country’s independence in 1971, although some data has exceeded this period, while the normal average of certain meteorological events is calculated with data for three decades.

Similar to Bangladesh, India’s upstream regions also saw record rainfall in June, according to Indian media.

Between June 1 and June 22, Indian media reported that Meghalaya recorded 161 percent more rain – 1,314mm of rainfall compared to a normal rainfall of 503mm.

Indian media reported that Mawsynram, one of the wettest places on earth, received 1,003mm of rainfall between June 16 and 17, the highest rainfall on record for 24 hours, surpassing the previous record of 945 in 1966.

Cherrapunjee, the second wettest place on earth, recorded 972mm of rainfall, its third highest single-day rainfall over the same period.

Scientists from the Intergovernmental Panel on Climate Change have previously warned of warmer climate influencing weather patterns and rainfall variability, which includes events in which a season’s maximum rainfall is recorded in two to three heavy rainfall events while the rest of the days would feature dry weather. spell.

“Due to climate change, a wetter climate has been predicted for this region,” Anjal Prakash, lead author of IPCC AR5 and IPCC Oceans and Cryosphere, told reporters following the recent floods.

Meteorologists in Bangladesh and India attributed the extreme rains to strong monsoon winds from the Bay of Bengal carrying far more moisture than ever before.

IPCC scientists have already explained the science behind warmer weather carrying more humidity. This is because warmer air holds more moisture, and that too for longer.

Another sign of the influence of climate change on the region’s weather pattern is the early onset of this year’s monsoon. Heavy rains upstream and in the interior of Bangladesh actually started as early as April, causing the first wave of flash floods.

The second wave of flooding occurred in mid-May.

“We are now witnessing another catastrophic flood in northern Bangladesh. In a short succession, we have huge floods as soon as the monsoon begins, which was not the case a few decades ago,” said AKM Saiful Islam, who teaches water and flood management. at BUET.

“We must prepare for the intensification of such unpredictable weather events in the future,” he added.

But the lack of information sharing between Bangladesh and India, coupled with man-made reasons such as river encroachment and deforestation, complicates the situation.

The amount of water from this year’s extreme rains dumped in the region has remained unknown, despite the region’s major rivers struggling to drain runoff from the extreme rains that triggered devastating floods 19 days ago.

Despite the drop in water levels of major rivers, three northeastern rivers are still flowing above their danger marks, with the Kushiyara flowing 80cm above Amalshid.

At the height of the flood, when Sylhet and Sunamganj districts were almost completely inundated by waters on June 20, when elder Surma broke its historic water level record of 7.29m in Derai , rising to 7.7 m over the following days.

Khalequzzaman, who teaches geology at US-based Lock Haven University, said sharing information was crucial for better flood management through effective flood forecasting.

“We need to work with upstream countries to immediately develop an integrated water-sediment management plan,” he said, adding that about 8 billion cubic meters of rain fell on the Meghna basin.