Owing to electoral compulsions, regularisation of these unauthorised colonies on the Yamuna floodplain had been a foregone conclusion.

The Delhi Development Authority (DDA), which reports to the Union urban development ministry, has decided against regularising dozens of colonies that have mushroomed over decades on the Yamuna's floodplain. Localities such as Sonia Vihar and Batla House Extension are on the list.

This decision has the potential of becoming another flashpoint between the Centre and the Delhi government. The Aam Aadmi Party's law minister-designate, Kapil Mishra, has already vowed to challenge the move.

The land-owning agency has also decided to suggest to the National Green Tribunal (NGT), which is monitoring a Yamuna revival plan worth crores of rupees, that no fresh construction should take place in the floodplain.

"It is a massive area. We will also issue directions to the registration department to ensure against sale-purchase of any property in this ecologically sensitive belt," DDA's vice-chairperson Balvinder Kumar told Mail Today.

However, the DDA's move itself is a U-turn of sorts. In 2013, it had moved to shrink by half the river zone, spread over 9,700 hectares in Delhi, to legitimise the illegal colonies it first allowed to mushroom. But the NGT had stayed the move.

Owing to electoral compulsions, regularisation of these colonies was a foregone conclusion. It is for the first time that DDA, custodian of the floodplain and land elsewhere in the Capital, has risen to the "need for saving the river".

The destruction of floodplain reduces groundwater recharge capacity and poses threat of flash floods. While DDA's latest move is good news for the river, it means dozens of colonies - like other areas that supported AAP in February's Assembly election - will stay unauthorised and civic amenities will not reach them.

"The DDA allowed construction of Commonwealth Games Village, Akshardham temple and other structures in the floodplain, but is finding fault with the colonies of common people," said Mishra, who fought for Yamuna's floodplain for years.

Mishra is an MLA from Karawal Nagar, where a large number of unauthorised colonies such as Sonia Vihar and Shriram Colony lie in the floodplain.

Expert panels appointed by the NGT have said existing structures like Akshardham temple and CWG Village should be treated as part of a special zone within the river zone. "We cannot ignore the river. It's vital for the city. But we must have a balanced, humane view. And, who allowed these colonies to mushroom? DDA officials only. If you don't regularise and provide facilities like sewerage to these colonies, they will pollute the river even more. We will fight to the finish," he said. "DDA has become like a property dealer. It has amassed Rs 40,000 crore but not spent anything on Delhi's infrastructure."

But environmentalists have a different opinion. Manoj Misra of NGO Yamuna Jiye Abhiyan (YJA), on whose petition the NGT is hearing the Yamuna case, said Delhi must value, protect and preserve its remaining floodplain. "The residents of these colonies have chosen to live in the river zone; they know they are at risk. After regularisation, the government may provide them certain amenities, but there would still be flood risk, as seen in Srinagar," he added.

The river, which meets Delhi's 70 per cent water needs, has turned into a sewer, and encroachment has reduced its channel to a narrow strip at various places.

If these are illegal colonies that won't get the legit tag, will the DDA plan a demolition drive next?

"It is not possible now for the government to go for demolition. But no fresh construction should be allowed. These colonies will remain illegal and fend for themselves. It is up to NGT to decide on our recommendations," the DDA vice-chairperson said. He said DDA will demolish all slum clusters and end all agriculture activity from the floodplain. "To ensure there is no further encroachment, we have identified 20 locations to install 100 CCTV cameras," Kumar said.

YJA said Metro depots and complexes should also work on a longterm relocation plan away from the floodplain. "Ditto for the Delhi Secretariat and associated structures. Delhi Transco complex opposite Sarai Kale Khan, which is bang in the middle of the floodplain, must be relocated," Misra said.

A plan prepared by the NGT panel says the Yamuna floodplain in Delhi and Uttar Pradesh should be a model of urban riverscaping to meet cultural, spiritual and religious needs of Delhiites, besides as a means of environmental education.