‘4 reasons’ floodwaters are receding slowly in Bangladesh

The water levels of many rivers are still above their danger points

The Bangladesh Meteorological Department has described the intense flooding in 11 districts near the end of August as ‘flash floods’.

Such floods usually inundate a wide area quickly, but the water usually recedes quite swiftly too.

However, this year’s flash floods are not retreating with the same speed. Districts like Feni were flooded a week ago, but the water has yet to drain away. Even in the areas where the water levels are on the decline, the pace of the ebbing is slow.

Discussions with meteorologists and climate experts revealed four main reasons for the flooding situation remaining largely unchanged until Sunday.

They say that simultaneous heavy rains in the Chattogram Division and the neighbouring Indian state of Tripura, the high level of mountain runoff, the tidal levels in the ocean, and the persistent rain in flooded areas has led to the extended flooding.

For these reasons, the floodwater has not receded after a week. Even on Sunday, little improvement could be seen.

According to the Water Development Board’s Flood Forecasting and Warning Centre, flood-affected areas saw the waters recede by an average of 20-30 cm between 9am and 6pm on Sunday.

Sardar Uday Raihan, the centre’s executive engineer, said: “This rate of decline can be described as slow to moderate. It is slower than the rate of water receding in other flash floods.”

Raihan noted two main reasons for the slow retreat of the water.

“One reason is that, the floods that happened in our country due to intense rain for the past three or four days also happened upstream. For this reason the water leaving the plains is leaving at a slow rate.”

“Another reason is that it is still raining. It is not as intense as before, but it is still raining. As a result, though the water is receding, it is not declining quickly.”

However, Raihan said the waters are likely to start retreating at a faster pace from Tuesday.

The water levels of the rivers reflected Raihan’s analysis. Many were still flowing above their danger levels. In some places, like Chattogram’s Mirsarai Upazila, the water is rising. There are reports of rising water in four of its unions on Sunday as well.

According to data from the FFWC, the Kushiyara River was flowing 13 cm above its danger point at 9am on Sunday. The water level only dropped by 1 cm over 24 hours.

The Kushiyara was also flowing 3 cm above the danger point at the Sherpur-Sylhet point and 2 cm above it at the Markuli point. However, the water levels at these points have dropped by 6 cm and 2 cm respectively over the past 24 hours.

The FFWC says that the Manu River was flowing 23 cm above the danger line at the Moulvibazar point at 9am on Sunday, but the water had dropped by 68 cm over the past 24 hours.

The Gomti River is flowing 78 cm over the danger line in Cumilla, but in the 24 hours to Sunday morning, the water level had dropped by 18 cm.

Rain was recorded in several districts on Sunday. Between 9am and 6pm, Teknaf saw 35 mm of rain, Naikhongchhari 24 mm, Lama 15 mm, Anowara 19 mm, and Noakhali 12 mm.

Feni is one of the districts worst hit by this round of flooding. Many parts of the district, including the Sadar town and other major population centres, are still inundated.

Of the 653 mobile communication towers in the area, 588 are still out of order. Despite ongoing efforts, these towers could not be made operational because of the strong water currents and lack of power. The disaster has hit the road network too.

In many ways, Feni is cut off from the rest of the country. For this reason, the WDB does not have any information on the Muhuri River, the overflowing of which led to the widespread flooding.

The other districts affected by the floods are Noakhali, Lakshmipur, Cumilla, Brahmanbaria, Chattogram, Khagrachhari, Habiganj, Moulvibazar, Sylhet, and Cox’s Bazar.

A monsoon low pressure system was formed over the Bay of Bengal and its west coast from Aug 17, according to the Bangladesh Meteorological Department. The low remained there for two consecutive days, causing rainfall in the hilly terrains of the coastal area and the southeast.

The water level in all rivers then began to rise.

The BMD predicted that the low would move to India's Bihar via West Bengal, but it entered Bangladesh and remained over the central regions until Aug 20, causing rainfall. There was a very heavy downpour on the night of Aug 20 which led to a 'flash flood'.

Climate change, river and water resources expert Ainun Nishat gave an explanation for the trend of very heavy rains.

"Due to climate change, everything has been thrown into disorder. This time we saw flooding from Sylhet to Bandarban. The low pressure moved to that side. Earlier, there used to be specific dates for when such weather systems would develop. But now there isn’t. Hence, there was such heavy rain all of a sudden," he said.

"Earlier, we always saw it raining near the end of Jaitra. The last three days of the Bengali month of Jaishtha and first four days of Boishakh always had rain. There used to be Kalboishakhi (norwester storms). But now, it’s nothing like that."

Experts have been saying for a long time that climate change is affecting Bangladesh. Hence, the seasonal weather is changing its character.

Prof Ainun Nishat reiterated these comments.

"This time the flood is a flash flood. The water is mountain runoff from the hilly areas that came to the plain land and will recede very slowly.”

Due to the nature of the seasons, Bangladesh usually sees the highest rainfall in July.

But meteorologist Omar Faruk said that there was less rainfall this July.

"The rainfall was less than usual this July but there were heavy downpours from Aug 16 to Aug 22. There was heavy rain upstream in India's Tripura and it rained heavily in the country. These two combined led to the severe flooding."

When asked why the floodwater was receding slowly, the meteorologist said the tidal water level has remained high in the sea since the rainfall started. Hence the floodwater was receding slowly, he explained.

Amid the current situation, the BMD forecast rain in different parts of the country until Tuesday.

Heavy rain is expected in Barishal, Khulna and Chattogram over the next 24 hours. Also, many parts of Dhaka and Sylhet divisions and some parts of Rangpur, Rajshahi and Mymensingh divisions are likely to see moderate rain.

Experts and meteorologists believe persistent rainfall as one of the reasons for the flood water receding slowly. The heavy rain forecast for the next 24 hours is not a good sign for the flooding situation.