Geo-tube sea walls to be set up

Chennai, 10/08/2010: Shoreline on Expressway near North Bharathy Nagar, Ennore on Tuesday. Photo: V. Ganesan.

The Water Resources Department proposes to establish geo-tube sea walls instead of concrete groynes as a measure to check tidal waves and to reclaim the shoreline along the northern and southern periphery of the city.

Officials of the department said geo-tubes, which are made of polypropylene, filled with sand, would be placed at points that are vulnerable to erosion. The tubes would be 20 metres long and 2 metres in diameter.

Can sustain shocks

Unlike the concrete groynes that are likely to collapse as a result of the wave action, the geo-tubes can adjust and sustain such shocks.

They are designed to withstand waves rising up to a height of even three to four metres.

Another advantage of geo-tubes is they do not require frequent maintenance.

It has been proposed to lay geo tube groynes on a six-km stretch of the shoreline from Ernavoorkuppam to Ennore in north Chennai. Similarly, geo tube wall comprising bags made of geo-textile materials would be laid for a 500 metre stretch near the Shore temple in Mamallapuram and on a 1.2 km stretch in Oyalikuppam near Kalpakkam, an official said. Such projects have already been implemented in Kerala and Andhra Pradesh.

The estimate prepared would be sent to the Institute of Hydraulics and Hydrology, Poondi, for analysis and then to the State government for approval.

Work is expected to begin early next year, an official said.

The project would be taken up with Rs.200 crore funding under the 13th Finance Commission to reclaim coastal landscape in Tamil Nadu. Nearly 50 per cent of the fund would be spent on the projects for Chennai region.

The department also plans to construct rubble mound sea wall near Ondikuppam and Appar Nagar in Tiruvottiyur covering a distance of 650 metre. Moreover, the existing 1.14-km-long rubble mound wall in fishing hamlets such as Anna Nagar Kuppam, Chinnakuppam and Tiruvottiyur Kuppam along Ennore Expressway would be strengthened at a total cost of Rs.15.85 crore.

Of the 13.5-km long shoreline along Ennore Expressway, 12-km stretch has already been provided with rubble mound walls. So, it is not possible to go for geo tubes in the remaining stretch.

The use of geo tubes would help in sand accretion and retrieve the lost coastline in a decade, the officials said.