After the scorching heat of summer comes monsoon as a blessing for Dhaka's “drained” citizens.
An insufficient and inefficient drainage network however, soon turns that blessing into a curse as the heavy downpours flood the city, submerging a large part of its roads and streets in semi-treated murky water and throwing its already hectic traffic, completely out of gear.
Water-logging in Dhaka is an outcome of several seemingly related factors – infrastructural limitations of respective authorities, lack of capacity in establishing a functional sewerage system by the authorities and their sub-contractors, and collective unawareness of the citizens who fail to realise that they have been playing a big part in choking the city’s drainage network.
Data available from the Dhaka Water Supply and Sewerage Authority (WASA) shows that the capital has 370km of storm sewerage network, and 2,840km long surface drains to discharge rain water 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 matter little in front of bigger numbers that represent the capital city – a population of about 1.7 million, 7,000 tonnes of daily waste generation, and an annual average rainfall of 1,900mm.
Dr Quazi Azizul Mawla, Professor of Architecture of BUET, who has done a lot of research on Dhaka’s sewerage system, said that one doesn’t need the understanding of an expert to realise why Dhaka gets deluged during monsoon.
“The rainwater has to be channelled out from the city to a lower plain and through a functional, properly-managed network of drainage systems, so that rainwater instantly runs into the low-lying retention areas.”
Now, if rainwater gets stagnates, it either means the drainage system is insufficient or it means the whole system is inefficient, said Prof Mawla adding that in Dhaka’s case, it is both. Dhaka must have at least 20 retention ponds the size of Hatirjheel to tackle the storm water. But the fact is, there is only one Hatirjheel in Dhaka.
He said that almost all the storm water drains in Dhaka were designed long ago and are not capable of handling the excess rainwater. “Dhaka’s drainage system was planned back in the early 20th century for a maximum rainfall of 25mm per hour, assuming that half the rain would be absorbed by the soil and only half would flow into the drainage system.”
However, with the onset of rampant and indiscriminate urbanisation, most areas are now paved with concrete or asphalt. As a result, very little rainwater is absorbed into the ground. Thus even at one inch per hour, the drainage system has to cope with almost twice its intended capacity, he said.
Besides, now WASA, the custodian of Dhaka’s storm water sewerage system, now has the capacity to drain out 20mm of rainfall through its pumping facility. That means, if the rainfall is above 30mm, it will take at least two hours to recede.
Meanwhile WASA and other respective authorities have engaged in some sort of blame game to shift the responsibility on others. They also have very little coordination amongst them.
During this government’s first tenure, in September 2012, Dhaka Wasa prepared a 23-year sewerage master plan involving US$2 billion to bring the whole city under its network.
However, in the last five years, the implementation of the first phase of that masterplan is going at a snail’s pace.
Kamrul Hasan Chowdhury, Chief Engineer of WASA, said the project work under the masterplan is currently underway. “But you have to realise that we have the responsibility to look after the drainage of 39 percent of the capital.”
He said that the problem is that they carry out the de-silting of drains once before the monsoon. “We however want to carry out the de-silting throughout the year but the budget to do so is only disbursed in April-May.”
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 simultaneously damaging the city’s drainage system, said the WASA Chief Engineer.
Md Mesbah ul Islam, Chief Executive Officer (CEO) of Dhaka North City Corporation (DNCC) said, that the duty of looking after whether the construction debris choke the drain or not falls on Rajdhani Unnayan Kortipokkho.
The CEO of DNCC said that, from their part, they have been trying to maintain their network of feeder drains. “But you have to understand that narrow drainage networks like feeder drains will not be sufficient enough to solve the water-logging crisis of Dhaka.”
He also stressed on the importance of reclaiming Dhaka’s 22 canals from the grabbers. “Without water bodies like canals, you cannot discharge the rainwater run-off even if you develop a network of sewerage lines,” he said.