Ganga floodplain: construction ban narrowed to 1-in-5-year flood zone

The Centre has amended the regulatory framework for the Ganga and its tributaries, introducing a tiered classification of floodplains based on flood return periods and replacing the earlier 'construction-free zone' wording with broader measures to reduce pollution and protect groundwater recharge.

The amendment, issued by the Jal Shakti Ministry through a notification dated August 7 and published in the Gazette on August 10, redefines the 'active floodplain' as the area submerged during a flood with a one-in-five-year return period. This is a departure from the 2016 order, which defined the floodplain as the area corresponding to the river's greatest flow or a flood with a one-in-100-year frequency.

Under the revised framework, the 'flood plain' now consists of three distinct zones: the active floodplain (inundated during a 1-in-5-year flood), a regulatory zone (between 1-in-5-year and 1-in-25-year floods), and a warning zone (between 1-in-25-year and 1-in-100-year floods). The notification, however, does not specify any construction permissions or prohibitions for the newly defined regulatory and warning zones.

The 2016 order prohibited construction of permanent or temporary structures for residential, commercial, industrial or other purposes in the Ganga, its banks, tributaries and the active floodplain, subject to specified exceptions and permissions. The latest amendment does not alter this prohibition. Instead, it redefines the active floodplain as the 1-in-5-year flood area, thereby narrowing the zone in which construction is barred. Under the earlier definition, the prohibition applied to a much larger area corresponding to the 1-in-100-year flood line.

The amendment also removes the term 'construction-free zone' from the order, substituting it with a requirement that the river's banks and floodplains be maintained to 'reduce pollution sources and pressures' and preserve their 'natural groundwater recharge functions' through necessary measures.

Observers have noted that while the new notification introduces a more nuanced floodplain classification, it leaves the regulatory status of the zones beyond the active floodplain unclear. The order itself does not outline what restrictions, if any, apply within the regulatory and warning zones, nor does it explicitly mandate that construction in those areas be subject to environmental appraisal.

The River Ganga (Rejuvenation, Protection and Management) Authorities (Second Amendment) Order, 2026, came into force on the date of its publication in the official Gazette. The principal order was first notified on October 7, 2016, and according to the notification, was last amended on May 7, 2026.

This move is part of the government's ongoing efforts to balance the ecological health of the Ganga with development pressures in riverine areas. By defining the active floodplain on the basis of a shorter return period, the extent of regulated construction is reduced, potentially affecting how the floodplains are used. The notification also underscores the need to preserve natural groundwater recharge functions, which are critical for water security in the surrounding regions. However, the absence of explicit guidelines for activities in the regulatory and warning zones leaves a degree of ambiguity that may need to be addressed through further rules or clarifications.