‘Seawalls, breakwaters are not a lasting solution to coastal erosion’

Though 45% of Kerala’s coastline is affected by coastal erosion, fixes like seawalls and breakwaters are largely ineffective and do not offer a lasting solution to the menace. Kiran A.S., scientist at the National Institute of Ocean Technology, Chennai, on Friday said that as per figures from 2016, as much as 36% of the Indian coastline is affected by erosion. Kerala is third in line after West Bengal and Puducherry, where 50% of the coastline is prone to erosion. Of all the States along the western coast, Kerala faces the maximum erosion, he said.

Mr. Kiran was speaking at a day-long workshop on prevention and possible solutions to coastal erosion organised by the Cochin University of Science and Technology (Cusat), Kerala Matsyathozhilali Aikyavedi and Coastal Area Development Agency for Liberation.

In Kerala, man-made causes like dredging of tidal inlets, development of ports and damming of rivers are largely responsible for coastal erosion, he said. Constructions along the coastline obstruct the movement of sediments causing erosion of material in some places and accretion in others. In other coastal states, erosion is mostly attributed to natural causes like sea level rise, cyclones and storms, Mr. Kiran pointed out.

Sheela Nair, scientist at the National Centre for Earth Science Studies who has worked on shoreline mapping in the State, concurred that anthropogenic factors like mining and the construction of harbours in recent years have been responsible for erosion. Of the 590-km-long coastline in the State, nearly 450 km is protected by seawalls, groynes or breakwaters leaving very little of the beach, she said. “There are very few natural, stable beaches left while there are 50 breakwaters and around 220 groynes,” she said. Since the Cochin Port is the only port in the country that carries out dredging all year round, it has had a significant impact on the coastline and groynes were put in place, she said. Beaches are a natural barrier to strong wave action.

Land-based seawalls like the one at Chellanam are usually not recommended as safeguards against the sea as they are vulnerable to vandalism — they can be cut open and destroyed easily, Mr. Kiran said. Some types of geotextile bags may also be destroyed by exposure to ultraviolet radiation. Seawalls will have to be submerged a few metres beneath the water for them to be effective, Mr. Kiran explained.

“The failure rate of seawalls is high. Seawalls and groynes of the same design will not be useful in all places and site specific studies are required,” said Krishnan B.T.P., chief engineer, Kerala State Coastal Area Development Corporation.

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Printable version | May 7, 2021 2:36:26 AM | https://www.thehindu.com/news/cities/Kochi/seawalls-breakwaters-are-not-a-lasting-solution-to-coastal-erosion/article29475025.ece

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