A proposed greenfield airport at Parandur near Chennai could significantly increase flood risks for the city, with a research organisation warning that an additional 10,000–12,000 cusecs of floodwater may enter the Adyar and Cooum rivers during peak rainfall if the project proceeds.

According to a report by Uvakai Research Foundation, Chennai’s rivers lack effective floodplains, making the city highly vulnerable when river flows exceed their carrying capacity. The organisation said the pre-feasibility report does not provide evidence that the Adyar and Cooum rivers, already operating beyond hydraulic capacity during extreme rainfall events, can safely accommodate the additional flood load.

The report also alleged that the pre-feasibility assessment prepared by the Tamil Nadu Industrial Development Corporation incorrectly classified the Parandur site as part of the Lower Palar basin. Hydrological analysis indicates that around 66 per cent of the project area lies within the Cooum river basin, while 34 per cent falls within the Lower Palar basin.

Further, the Kamban Kalvai channel running through the site reportedly conveys water towards Chembarambakkam Lake in the Adyar basin, establishing a functional linkage with the Adyar river system. The report stated that runoff from the airport site would ultimately flow through Chennai, a densely urbanised and flood-prone city.

Uvakai Research Foundation criticised the project for proceeding without adequate hydrological justification and called on state and central governments to halt further approvals and land-use conversions. It also urged authorities to conduct independent, basin-scale hydrological assessments and flood modelling before moving ahead.

The concerns echo findings from the Comptroller and Auditor General’s 2017 report on the 2015 Chennai floods, which highlighted the absence of basin-based planning despite the city’s flood risks being driven by interconnected catchments. The CAG had also pointed to fragmented drainage and flood control measures implemented without accounting for upstream runoff and downstream carrying capacity.

The foundation warned that the Parandur airport proposal reflects similar governance gaps and could repeat past mistakes, potentially exacerbating Chennai’s flood vulnerability if not addressed through comprehensive hydrological planning.