POST TIME: 13 July, 2019 12:31:49 AM / LAST MODIFIED: 13 July, 2019 12:57:58 PM
Grabbed canals, silted drains add to woes
Dhaka drainage inadequacy

Grabbed canals, silted drains add to woes

Pedestrians struggle to wade through stagnant rainwater on an inundated road at Arambagh yesterday while a shopkeeper (inset) haplessly sits inside his shop that has been invaded by rainwater at Paschim Tejturi Bazar in the capital, indicating the dire state of the city’s drainage. Star Mail photos

Amid the searing summer heat, rains come as blessings for the ‘drained’ Dhaka folks. However, every time a torrential shower lashes the city, large parts of the capital go under murky water, throwing the already wobbling traffic out of gear. Waterlogging in Dhaka is an offshoot of several related factors—infrastructure limitations including insufficient drainage network, lack of coordinating among various authorities to solve the crisis, and lack of awareness of citizens who are dumping polythene and other non-biodegradable wastes in the city’s drainage network.

Some key limitations of the Dhaka drainage system are illegal grabbing of the 22 canals that carry Dhaka water outward and inadequate de-silting of drains, say people concerned. Data available from the Dhaka Water Supply and Sewerage Authority (Wasa) shows the capital has a 370-km-long storm sewerage network and 2,840-km-long surface drain to discharge rainwater into 22 canals.

At the same time, Dhaka North and South City Corporations collectively maintain over 2,000km of feeder drains (narrow sewer system) to carry rainwater and liquid waste from homes into canals and the wider diameter storm sewer system.

However, these figures pale into insignificance when one looks at an annual average rainfall of 1,900mm and the capital’s population of about 17 million who generate 7,000 tonnes of wastes daily.

Dr Quazi Azizul Mawla, professor of architecture at BUET, has done extensive research on Dhaka’s sewerage system.

”One doesn’t need to be an expert to realise why Dhaka gets flooded during the monsoon,” he said.

“The rainwater has to be channelled out from the city to a lower plain. Through a functional, properly-managed network of drains, rainwater should instantly run into low-lying retention areas,” he added.

“Dhaka’s drainage system is insufficient and the whole system is inefficient. There should be at least 20 retention ponds of the size of Hatirjheel to tackle storm water. But there is only one Hatirjheel in Dhaka,” he noted.

He also said almost all the storm water drains in Dhaka were designed long ago and they are not capable of handling the excess rainwater.

”Dhaka’s drainage system was planned in the early 20th century for a maximum rainfall of 25mm per hour, assuming that half the rain will be absorbed by the soil and only half will flow into the drainage system,” he added. However, with the onset of rampant and indiscriminate urbanisation, most areas are now paved, concreted or asphalted. As a result, very little rainwater is absorbed into the ground. So, the drainage system has to cope with almost twice its intended capacity in case of rain amounting to one-inch per hour, he said.

Besides, now the Wasa, the custodian of Dhaka’s storm water sewerage system, has the capacity to drain out 20mm of rainfall through its pumping facility. It means if the rainfall is above 30mm, it will take at least two hours for the water to recede.

Wasa and other respective authorities, meanwhile, are engaged in a kind of blame game to shift the responsibility to others, he said.

They also have very little coordination among them. During the current government’s first tenure, in September 2012, Dhaka Wasa prepared a 23-year sewerage master plan involving USD 2 billion to bring the whole city under its network.

However, in the last five years, the implementation of the first-phase of the masterplan has been progressing at a snail’s pace.

Taqsim A Khan, managing director of Wasa, said the project work under the master plan was on course. “But you have to realise that we have the responsibility to oversee the drainage of 39 per cent areas in the capital. We carry out our work every year in the areas under our jurisdiction,” he added,

He said the problem was that they do the de-silting of drains only once before monsoon. “We, however, want to carry out the de-silting

throughout the year. But the budget to carry out the work is disbursed only in April-May,” he added.

Meanwhile, the capital’s civic agencies have turned a blind eye to the construction debris lying unattended near various drains across the

city. The construction work, which is supposed to give a facelift to the capital, is at the same time damaging the city’s drainage system.

Mohammad Abdul Hai, chief executive officer of the Dhaka North City Corporation (DNCC), said it was the duty of Rajdhani Unnayan Kortipokkho to see whether construction debris was choking the drains.

He also said that, on their part, they were trying to maintain their network of feeder drains. “But you have to understand that a narrow

drainage network like the feeder drain will not be sufficient to resolve the waterlogging crisis of Dhaka,” he added.

He stressed the urgent need of reclaiming Dhaka’s 22 canals from grabbers. “Without waterbodies like canals, we can’t discharge the

rainwater runoff even if we develop a network of sewerage lines,” he said.