Filling up of eighty percent low lying areas and water bodies in the capital by encroachers is the main reason for water logging in the city, since those used to be the major channels for draining out rain water, said experts.
The rivers around the city were also encroached upon over the years worsening the situation, they added.
The experts cautioned that the problem of water logging in the city will fast deteriorate if the lost water bodies are not recovered and rehabilitated immediately.
Abu Naser Khan, chairman of Save the Environment Movement said, "Although the number of storm drains in the city was much lower 15 years ago, still the residents did not suffer from the severe water logging they face now, as there were enough unencumbered water bodies and low lying areas in the city, eighty percent of which are now filled up by encroachers."
Most of the city's 43 canals have been encroached upon and totally or partially filled with dirt over the years, said architect Iqbal Habib who is also a member secretary of the Urbanisation and Good Governance Committee of Bangladesh Paribesh Andolon.
Dhaka Water Supply and Sewerage Authority (Wasa) took an initiative to recover 26 of those canals from the grip of encroachers following a decision of a high-powered committee formed by the government a few years ago, but the move failed to achieve much success.
Many of the recovered canals were encroached upon again since those were not re-excavated following the recovery, said a Wasa official.
Low lying areas including the eastern fringe of the city are being filled up relentlessly in the name of development, resulting in water logging, said Iqbal Habib.
It is absolutely necessary to re-excavate recovered canals soon after the recovery in order to get full benefit of the drive, he added.
Box culverts, which were constructed on different canals or water bodies, also remain clogged for lack of cleaning, contributing to the problem, Habib said adding, monitoring of storm drains and the box culverts is also necessary to curb the debilitating water logging that plagues the city every monsoon.
An immediate coordinated initiative of Wasa, Dhaka Electric Supply Authority (Desa), Dhaka City Corporation (DCC), Rajdhani Unnayan Kartripakkha (Rajuk), and the local administration is an imperative for solving the problem of water logging in the city, he stressed.
Another Wasa official attributed the city's water logging problem primarily to an outdated and inadequate drainage system. "A proper drainage system does not only mean having a few sewerage lines and drains, it means building up a network that connects the drains and sewerage lines with natural water bodies such as ponds, lakes, and canals," he quipped.
Although, Dhaka had hundreds of ponds, natural canals and lakes, those were filled up due to the city's unplanned growth and wholesale urbanisation in the last two decades, he said.
Managing Director of Wasa Raihanul Abedin blamed unplanned urbanisation for the wholesale filling up of the water bodies.
Due to the wholesale encroachment, many canals which used to be wide have become narrow, he said.
"We demolished 657 illegal structures on 17 encroached upon canals till March 31, 2007, but due to High Court injunctions against demolishing many other similar illegal structures we could not expand the drive," he said adding that many slums built on encroached upon canals had to be left out of the drive since the World Bank financed $148 million project for recovering the canals puts a condition that no slum can be demolished without prior rehabilitation of the residents.
The 17 recovered canals however will be developed with walkways built and trees planted on the banks, in a bid to make it difficult to encroach upon the water channels, Raihanul said.
"We also could not expand the recovery drive to six canals that were under the control of National Housing Authority at the time, but a process is now on to bring those under Wasa's control," he added.
Other sources in Wasa said filling up of Katasur canal is the main cause of water logging in Rayer Bazar and Mohammadpur areas while encroachment on Ramchandpur canal is causing water to be trapped in Islambagh, Nawabganj and Hajaribagh areas.
Dholai Khal, a canal in the southern part of the city which used to be more than 30 metres wide was turned into a 2.5 metres wide box culvert, the sources added.
Narrowing of the canal led to water logging in the areas of Bangladesh University of Engineering and Technology (BUET), Bakshibazar, Husaini Dalan, Nimtoli, Nazimuddin Road, Bangshal, Aga Sadek Road, Gandaria, Postagola and Faridabad, the sources added.
Filling up of 5 to 6 jheels [swamps] through encroachment has been causing severe water logging in Bashabo, Khilgaon and Mugda areas.
Since encroachers filled up a large swath of Jirani canal and DCC constructed a road through it, Motijheel and Kamalapur areas have been getting inundated by trapped rain water during monsoons, the sources said.
Encroachment on Segunbagicha canal at Maniknagar and Manda has been causing water logging in Shantinagar, Inner Circular Road, Arambagh, Fakirerpool, Motijheel, Dilkusha and Sayedabad areas while encroachment on Jirani canal and Shahjahanpur canal is causing drainage problems in Malibagh, Mouchak and Shantinagar areas, the sources added.
Encroachment on Shahjadpur canal is preventing flushing out of rainwater and wastewater from Kuril, Progoti Sarani and adjacent areas.
Encroachment on some parts of Begunbari canal is responsible for water logging in Gulshan 1, Tejgaon and Mohakhali areas, the sources said adding since Mohakhali canal was encroached upon Nakhalpara, Arjatpara, Rasulbagh and Shahinbagh areas have been plagued with the problem of water logging.
Encroachment on five branches of Kalyanpur canal is causing water logging in Taltala, Agargaon, Kazipara, Shewrapara, Barabagh, Mirpur 1 and adjacent areas.
Eastern Housing Project in Pallabi and its adjacent areas have been facing water logging as Diyabari canal was partially filled by different real estate developers. The canal used to carry rain water to Goranchatbari pump house to be pumped out, said a Wasa official.
Residents in cantonment, DOHS, Kala Chandpur, and a section of Baridhara have been suffering from water logging in the areas as a pipeline for draining out water set up 20 years ago by Rajuk has been clogged, thanks to no initiative for cleaning the pipeline since its construction, the Wasa official added.
Encroachment on Ibarahimpur canal has been causing water logging in Uttara and Banani areas, while clogging of the main sewerage line of the areas has worsened the situation, the official said.
Storm drains and surface drains of both Wasa and DCC are also not maintained properly, said a DCC official.