B canal is plan A to save Chennai from floods

Last Dec's devastating floods in South Chennai exposed the gross neglect of the 218-year-old Buckingham Canal, a lifeline for the flood-prone city as it helps drain floodwater. This colonial-era waterway, once a vital trade artery, now struggles to manage floodwater due to silt buildup, reduced width, and encroachments. As the monsoon season looms, Chennai's residents face the spectre of another deluge.

The 48 km-long canal, stretching from Ennore to Muttukadu, was originally designed for salt, wood and fuel transportation. However, since the 1970s, it has been forced to carry the city's sewage, garbage and floodwaters. The consequences are dire: 26,300 encroachments, including MRTS pillars, have narrowed the canal, exacerbating inundation in areas reliant on it for drainage.

Decades of official neglect and public projects have pushed the canal into oblivion. TNEB's dumping of fly ash and hot water from the Ennore thermal plant into the canal has caused significant silt build-up. The Kodungaiyur marshland's conversion into a dumpsite in 1989 added toxic leachate to the canal, while excess sewage from the Kodungaiyur sewage pumping station now overflows into it. The Chintadripet to Indira Nagar stretch in Adyar is heavily encroached, narrowing from its original 100 m to just 5-15 m. MRTS pillars and retaining walls have worsened flooding in areas such as Mylapore and Kotturpuram, which did not experience floods of this magnitude before the 1980s.

"The canal was never meant for floodwater drainage. It doesn't have a natural unidirectional gradient. From Kodungaiyur, Vyasarpadi, and Washermanpet, floodwaters enter the canal and go north to Ennore Creek for drainage, while in the south, it carries water to Muttukadu," said Udhaya Rajan, Director, Uvakai Research Foundation, a think tank focused on waterbodies.

Metrowater sewage pumping stations in Kodungaiyur and Kotturpuram release sewage into the canal when their capacity is exceeded. "This constant influx of sewage has resulted in silting in the canal," said Udhaya. According to WRD, the canal should be 3 ft below mean sea level, but it now sits 3 ft above it, due to sludge accumulation.

Recognizing the canal's critical role in flood mitigation, the government has proposed restoration projects since 2000. However, most of them were shelved due to fund crunch and failure to remove encroachments. A 2014 proposal to construct a diversion channel was abandoned due to the 100 crore cost of acquiring patta land. This would have helped south Chennai face floods of a lesser magnitude.

WRD's latest 1,700 crore restoration proposal aims to revive the central canal by removing 3,000 encroachments and plugging sewage outfalls. A detailed project report is underway.


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