Urban wetlands are Chennai's first line of defence against floods. Discuss in the context of the Pallikaranai marsh and the Wetlands Rules, 2017.

The Ramsar Convention calls Pallikaranai Marsh an "aquatic buffer" for the flood-prone Chennai and Chengalpattu districts [1]. It covers about 1,247.5 ha and became a Ramsar site in 2022 [1][2]. Its value as a flood defence depends on how well the law protects both the marsh and the land around it.

Pallikaranai as Chennai's flood defence

• Sponge function: the marsh soaks up water in wet periods and releases it in dry spells, which reduces flooding in southern Chennai [1].
• Ecological buffer: it supports about 115 bird species, plus fish and amphibians. This shows the marsh is a working ecosystem, not wasteland waiting to be built on [1].
• A weakening defence: the Ramsar record lists household sewage, urban wastewater, invasive species and droughts as threats [1]. Builders' pressure on the marsh's edges led the NGT to ban construction within 1 km of its boundaries. Developers, including CREDAI-Chennai, are challenging that ban [3].

Role of the Wetlands Rules, 2017

• Decentralised regulation: the Rules were notified under the Environment (Protection) Act, 1986. They give management to State Wetlands Authorities and aim at "wise use" of wetlands [4].
• Zone of Influence (ZoI): activities in a notified wetland and in its ZoI need State permission [5].
• In practice: the TNSWA has proposed an interim ZoI of 36 survey numbers (128.19 ha), to apply until detailed studies fix a final ZoI [3].

Gaps

• Thin buffer: the interim ZoI is about one-tenth the size of the marsh [1][3]. It is much smaller than the 1-km ring.
• Legal overlap: the Rules do not apply to wetlands governed by forest laws [5]. Yet Pallikaranai is a Reserve Forest [1], which blurs who is responsible for it.
• Narrow scope: a ZoI controls building, but it cannot stop sewage flowing into the marsh [1].
• Litigation instead of science: the final ZoI is still waiting for studies, while the interim line is being settled in the High Court [3].

Way forward

• Set a deadline for a final ZoI based on hydrological studies, and write it into Chennai's master plan.
• Treat sewage before it enters the marsh. Make the TNSWA's site-selection criteria public.

Protecting Pallikaranai is a better flood defence than any amount of new drains. The Wetlands Rules provide the framework. What is needed now is a study-based ZoI and control of pollution entering the marsh. This would advance SDG 6.6 (protecting water ecosystems) and SDG 11.5 (reducing disaster losses), and fulfil the duty to protect the environment under Article 48A and Article 51A(g).