The operation will affect nearly 4,000 homes
The Karachi Metropolitan Corporation has started work on widening the Gujjar Nullah. It is one of the three stormwater drains that are being widened to ensure a smooth flow of rainwater.
The Sindh government decided to remove encroachments around drains following the August 2020 urban floods in the city.
It has tasked the NED University’s Infrastructure Engineering and Urban Development Department with chalking out a permanent technical solution to the issue. The NED University team decided to widen the Mehmoodabad, Gujjar and Orangi nullahs first.
The recommendations and technical study of Gujjar Nullah was submitted to the Sindh government on December 31, 2020. The 12.58km drain starts from New Karachi near Noorani Muhallah and ends at Liaquatabad near Haji Mureed Goth.
“As per the final plan, around 4,000 houses would be affected on both sides of the Gujjar Nullah,” said Dr Adnan Qadir, the NED Infrastructure and Urban Development Department chairman.
The NED team has finalised its survey report along with the hydrological and hydraulic analyses of the drain.
A hydrological analysis is the study of transformation of rainfall into runoff, while a hydraulic analysis studies the motion of liquids in relation to fluid mechanics and fluid dynamics.
The plan is to widen the Gujjar Nullah between 35 feet and 120 feet. “We have recommended 35-feet width at the zero point and 120-feet at the point where it ends,” Dr Qadir said.
The width of the drain currently varies from 15 feet to 87 feet. It’s 33 feet on the average.
The depth of the drain is not an issue, according to the NED expert. It will be increased by another 3 to 4 feet after cleaning the drain.
The NED Infrastructure Engineering Department was working on two designs during the technical study of the drain. The designs were the Liberal Model and the Conservative Model.
The Liberal Model enables stormwater drains to bear up to 270mm rain for 12 hours. This means 270mm rain would not affect the city in this duration.
The duration decreases to three hours in the case of Conservative Model. It means that drains would overflow three hours after it rains 270mm.
The Sindh government chose the Liberal Model in Gujjar Nullah’s case, Dr Qadir said. The NED team has also proposed a 30-feet road on either side of the drain to connect with the Lyari Expressway.
The KMC has been marking houses around the Gujjar Nullah for demolition, KMC Katchi Abadi Senior Director Mazhar Khan said. The process will be completed by January 31.
The demolition of these houses and structures will start February 3, according to Khan. Soft encroachments will be removed first.
KMC Anti-Encroachment Senior Director Bashir Siddiqui said the demolition work around the Mehmoodabad Nullah will be completed by Monday. The KMC anti-encroachment team will then move on to the Gujjar Nullah, he added.
There are 41 major stormwater drains in Karachi. Of them, three were picked for the technical solution. The first one was the Mehmoodabad Nullah. The KMC started demolishing structures along the drain from January 4. Over 200 houses were to be demolished in the operation. The Gujjar Nullah is the second drain to be widened.
The Orangi Nullah is the third one. Over 2,000 houses would be affected in the operation around the drain.