New Delhi: Delhi Development Authority (DDA) has informed National Green Tribunal that it will complete a drone survey of the Yamuna floodplain, or the O zone, in about two months. The survey area spans 165 sq km and includes the buffer areas.The O zone is the entire floodplain along the 22-km stretch of the Yamuna in the city. DDA has reclaimed 7 acres after demolition drives on April 16 and 17 at Madanpur Khadar and Jhangola villages and Revenue Estate-Indraprastha, all within the zone.The tribunal took suo motu cognisance of a TOI report in 2024, titled “161 illegal colonies on O zone making river water toxic.” The report highlighted that colonies with 2.3 lakh households were unattached to the sewer network and were contaminating the river.In a report dated April 20, DDA told NGT that the boundary of the zone had been digitised based on the approved planning document and the khasra layer, as provided by GSDL, was added over the available digitised boundaries of the zone. The drone survey is part of the second phase of documenting the zone.“The drone flying operations for the second phase started in the Green Zone on Feb 5,” DDA said. The Survey of India has stated that with an average output of approximately 3.5 sq km per day per team, two teams would require about 18 additional working days to complete surveying the remaining 122 sq km, the authority told NGT. This was subject to the availability of permissions (ATC etc.) and favourable weather conditions, the report added.The Green and Red zones are part of the O zone.DDA added that the timeline pertains only to the drone survey. About another month is required for post-processing work.DDA said that it has requested the land owning agencies, such as MCD and Land and Development Office, to remove encroachments on their respective land.DDA said it has designated officers to ensure that there is no further encroachment on the O zone with continuous monitoring, and it has asked MCD to do so too.On April 10, DDA sent the copy of the high court orders to the commissioner of police “with directions to ensure that all station house officers” within the O zone maintain vigilance against unauthorised constructions and encroachments and “provide assistance to DDA whenever required,” the report added.