The Hindu : Kerala News : `Coastal terrain may have saved southern Kerala'

Online edition of India's National Newspaper
Wednesday, Dec 29, 2004

Kerala

Kerala

`Coastal terrain may have saved southern Kerala'

By T. Nanda kumar

THIRUVANANTHAPURAM, DEC. 28 . On Tuesday, as the State was struggling to come to grips with the havoc wrought by the tsunami waves that swept in from the Bay of Bengal, scientists began grappling with the question of why the coastal areas in central Kerala were hammered by the huge surges while the southern parts escaped the fury.

The destructive impact of the seismic waves was determined by the coastal terrain, seabed topography and the orientation of the coast, it has emerged. One of the major reasons for the variance in intensity is attributed to the geomorphology of the coast.

Hilly coasts like Thiruvananthapuram were spared the impact while low- lying areas like Kolachel in Tamil Nadu and Vypeen and Thrikkunnapuzha in Kerala bore the brunt of the raging sea.

The orientation of the coast is another major factor. While Kolachel was openly exposed to the waves advancing from the South, the orientation of the coast from Muttam to Vizhinjam and the high terrain along this stretch resulted in minimum impact. The low-lying areas between Vizhinjam and Thankassery were the worst affected. After Thankassery, the straight coast up to Ponnani witnessed a uniform impact.

A team of scientists led by the Director of the Centre for Earth Science Studies, M. Baba, came up with these conclusions after touring the worst-affected areas from Azheekal to Thrikkannapuzha on Monday.

Seabed topography

According to the scentists, a third factor that had contributed to the variance in impact was the seabed topography along the coast, which determines the transportation of waves and the wave energy.

The low impact of the tsunami in the region stretching from Neendakara to Chavara is attributed to the unique bathymetry of the region which contributes to the divergence of the waves and dissipation of their energy.

Northwards of Chavara, the bathymetric profile is conducive to convergence and amplification of the waves.

This, according to the scientists, explains why the `barrier island' between the sea and the backwaters from Chavara to Thottapally took the full impact of the waves, which reached a maximum height of 15 to 20 feet at Azheekal, the worst-affected area.

While Thrikkannupuzha was also severely battered, the low population density in the region ensured minimum casualty. The waves lost intensity as they moved further North, leaving the northern coasts relatively unaffected.

`Implement CRZ norms'

Dr. Baba said the devastation wrought by tsunami had highlighted the need for an integrated coastal zone management strategy for the State. He feels that the Government should take immediate steps to implement the Coastal Regulation Zone norms and prepare a masterplan to create a buffer zone for the interplay of sea and land.

Coastal management

The urgent priority is to move habitation away from the shoreline to ensure that people are not directly exposed to such calamities. Rehabilitation measures should be integrated with scientific coastal management," he says.

"Though tsunami is a rare phenomenon occuring perhaps once a century or so, sea level rise triggered by global warming is a reality. Even monsoon waves may be higher in the coming years," he adds.

Responding to pleas for construction of more sea walls, Dr. Baba said, "A sea wall offers no protection against tsunami. At best, it will check temporary sediment transport."

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