The Public Works Department (PWD) appointed a consultant earlier this week to draw up a drainage master plan for the Najafgarh basin in Delhi, officials aware of the matter said on Thursday. The authorities floated the tender in May last year and after selecting the consultant, gave him a year to complete the project, they said.
“The Irrigation and Flood Control Department has already done initial topographic surveys and other studies. The consultant must now use these to come up with viable and actionable action points. The objective of this drainage master plan is to improve the drainage network so that the system can handle the monsoon rain without being overloaded,” said a senior PWD official.
According to the draft Delhi Master Plan 2021, the estimated population of Delhi is around 25 million and the total urbanized area is likely to be around 920 square kilometers.
“Due to the changing geographical and demographic conditions over the years, it is important to modernize and modify the drainage network to handle the discharge. Over the years, there have also been changes to the system, interventions in the solution in some places, blocking and interference in other places. All this needs to be researched and solutions implemented,” said another PWD representative.
According to the IIT report, the main problem areas of the Najafgarh basin are congestion of sewers due to sinkholes at many places and drains bringing rainwater from the area outside Delhi. It suggested making changes to the cross-section of the sewers or rejuvenating 140 small bodies of water in the basin to serve as temporary storage for runoff. Another suggestion was to use public parks as charging zones.
In 2021, the Delhi government entrusted the work to PWDs and asked the ministry to come up with three separate plans for the three major drains of Delhi in the Najafgarh, Barapullah and Trans-Yamuna basins. The Najafgarh Basin bid was first opened in 2021 and work has been awarded now.
Najafgarh is the largest canal in the National Capital Territory (NCT) of Delhi. It enters South West Delhi from Haryana. It travels 57,489 km before joining the Yamuna, downstream of the Wazirabad Barrage. In south-west Delhi, the drain carries flood water, sewage from Haryana and surface run-off from the adjacent watershed.
“Nearly 30.943 km stretch of the canal passes through the south-west district from near Dhansa to Kakraula. Thus, nearly 53.82% of the length of the Najafgarh drain flows through South West Delhi. Moreover, from Dhansa to Kakraula regulator, 28 small canals join this canal and beyond Kakraula canal, nearly 74 big and small canals join Najafgarh canal. The subsidiary drain is the second largest drain in the city, which joins the Najafgarh drain just before its mouth into the Yamuna. About 71 small drains connect to the supplementary drains,” says a report by the Irrigation and Flood Control Department.
Najafgarh drainage includes three main blocks – Alipur, Kanjhawala, Najafgarh and some urban areas of South West Delhi. The total area of the Najafgarh drainage basin in Delhi is approximately 977.26 km2.
Experts say the master plan is not a zone plan and can only suggest broad measures like the IIT report did. However, the consultant must dig deeper.
“The city’s stormwater system plays a vital role in mitigating urban flooding. While developing a stormwater master plan for an existing city, it is essential to take note of the existing ground situation, an in-depth understanding of peak rainfall data along with intensity and also geological understanding. The plan may consider including strategies for upcoming or greenfield areas specifically,” said Prerna Mehta, Associate Program Director, Sustainable Cities and Transport, WRI India.
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