Shrinking marshland causing floods in Chennai

(Chennai, Dec 8) Shrinking marshlands and the inability of a major canal to carry water from heavy rains and overflowing reservoirs are the main reasons for flooding here, say environmentalists.

"Due to garbage dumping and massive reclamation, the Pallikarnai marshland on the south of river Adyar has shrunk to 500 hectares, about one-tenth of its size," said R.J. Ranjith Daniels, an ecologist and environmental activist with Care Earth.

"The ecosystem provided by the marshland was to store and drain excess water from all around. The natural gradient is towards the Buckingham Canal and finally into the sea," Ranjith told IANS.

Buckingham is a salt-water navigation canal, running parallel to the Coromandel Coast for 420 km, from Krishna district in Andhra Pradesh to Villupuram district in Tamil Nadu.

The Adyar river meanders through the city, via Besant Nagar and the Theosophical Society in south Chennai, to meet the sea in the Santhome-Foreshore Estate area.

Here the government has built a slum resettlement colony, and multi-storeyed housing estates have come up, blocking the natural drainage pathway of the river basin into the sea. The original silting pattern here has shifted due to the buildings.

"With each hectare running to 10,000 sq m, the surface of water in the marshland would be five million sq m. Even if the depth of water was calculated to be one metre, the volume in the marshland was five million cubic metres. We are looking at five million tonnes of water pressure. During monsoon, the pressure increases manifold," Ranjith said.

But sewage and industrial effluent dumped into the canal and silting have left the waterway stagnant. The North Chennai Thermal Power Station discharges hot water and fly ash into the canal as well.

On the east of the Pallikarnai marsh, running north-south is the East Coast Road. The road goes past residential areas like Kottivakkam, Palavakkam, Neelankarai, Injambakkam - all flooded in the Dec 2 deluge. There is no way for the water from the west side of the East Coast Road to get to the beaches or the east side.

As many as 45,000 people have been evacuated from the banks of the Adyar river due to the incessant rains over the last week. However, 300,000 people in southern suburbs of the city continue to suffer due to waterlogging.

Chief Minister J. Jayalalitha has called for a long-term solution to tackle flooding in Chennai's southern suburbs, as the Buckingham Canal was unable to clear drain water from south Chennai through the Pallikarnai swamp.

She ordered a detailed investigation to have a regulated canal (straight cut) direct to the sea from the canal.

The Buckingham Canal runs north-south, approximately one kilometre away from the coastline, and near Basin Bridge north of here, it outflows from the Cooum and Adyar rivers. Nearly 31 km of the canal runs within the city limits of Chennai.

O.M. Murali, an expert of the WTI Advanced Technology Ltd., has suggested the use of geographic information system (GIS), global positioning system (GPS) and remote sensing (RS) data to plan drainage for Chennai but there have been no takers.

CHENNAI, DECEMBER 4: Chennai now has a different kind of water problem: the problem of plenty.
With the city’s reservoirs overflowing following the heavy battering of the state’s northern districts by the northwest monsoons, the Cooum and the Adyar rivers have swollen, flooding parts of the city and suburbs.
About 75,000 people in Chennai were evacuated and sheltered in over 140 relief centres. The Adyar that cuts across the city was in full spate, washing away hutments on its banks and flooding residential colonies in Kotturpuram and Little Mount areas in southern Chennai, forcing residents to vacate their houses and ground floor apartments.
In some areas, water levels reached the first floors.
Several areas were plunged into darkness as the state electricity board cut off power supply. About 45,000 residents were evacuated from the Adyar river banks.
A worried city police monitored traffic movement on the Saidapet bridge as the water level rose steadily due to heavy inflows from the Chembarambakkam reservoir.
About 12,000 cusecs of surplus water from the already-full Chembarambakkam Lake, one of the main sources of the city’s drinking water, was discharged, flooding several parts of the city.
The Cooum river, which traverses through the city, was in full spate as well due to release of 13,000 cusecs of water from Poondi reservoir and flooded many parts of the city.
Though the rain relented in Chennai and Kancheepuram districts, it continued to lash Thiruvallur for the third successive day.
Chennai experienced respite since Saturday morning. But this was not good news for those marooned in Kotturpuram, Velachery, Madipakkam, Pulianthope and Vyasarpadi. The incessant rains on Friday last resulted in swelling rivers and overflowing lakes and tanks in and around the city. In 24 hours until 8.30 am on Saturday, the city recorded 23.4 cm rainfall, Thiruvallur district, north of Chennai, 23 cm and Chengalpattu in Kancheepuram district, to the south, reported 15 cm.
Tambaram, another badly affected southern suburb, received the maximum rainfall of 31.4 cm. The Tamil Nadu Electricity Board disconnected power connection in several flooded parts of the city. Chief Minister, J Jayalalithaa, who inspected the affected areas in the city today, described the flood situation as ‘‘complex’’.
Relief operations were being undertaken on a war-footing, she said. The entire administrative machinery has geared up to tackle the challenge. All residents in low-lying areas were warned through the public address system and mass media about the flood. While all the boats available with the state fisheries and Fire Service departments were being used, Navy boats too, had been sought to rescue marooned people, she said.
In Tiruvallur district, lakes had filled up and heavy rains resulted in breaches of about 35 tanks. More than 70 relief centres had been set up and 50,000 people wer\e being provided with food today. In Kancheepuram district, more than 50,000 people were evacuated from vulnerable areas and accommodated in about 50 relief centres.