26 Dec 2018 06:11am IST
On December 26, 2004, the Indian scientific community was jolted by a powerful oceanographic event that no one had expected. Virulent sea waves resulting from the Indian Ocean tsunami struck Tamil Nadu coast. The socio-economic havoc was massive. The loss of life (8700 deaths) and property was overwhelming and the monetary loss (Rs 3242 crores) was enormous. Coastal scientists have not fulfilled societal obligations by warning implications of beachfront development. The tsunami that demolished large parts of the south Indian sea front was a grim reminder that all is not well with the way Indian coasts are colonised. And 14 years later, and the tsunami forgotten, it is business as usual in our littoral States.
Tsunami waves rose from 0.7 to 6.5m above sea level and induced flooding from 31 to 862m from the swash zone; the average inundation was around 247 m. The tsunami profoundly transformed the face of Tamil Nadu coast: 1. Frontal casuarina forests were the only portions attacked, bent, and stripped of its leaves by wave up-rush; large parts remained intact. Similarly, the coconut groves and date palms were unaffected. 2. Loss of life and property was identified only along the frontal strip ranging from 6 to 132m from the dune line. The worst affected was the Keechankuppam-Akkaripettai village strip of around 2 km where stone-walled houses were razed to rubble; around 6000 dwellers perished. 3. Over topping and over wash was noticed at places, as evidenced by wave-induced gaps along the dune ridges. Frontal sand dunes were damaged, some were breached, and others were eroded. These edifices withstood virulent waves. 4. Dune plants were uprooted and removed, often leaving no trace of frontal dune vegetation. The most affected dune vegetation comprises ‘ipomoea’ creepers and ‘spinifex’ that carpet frontal sand dunes. 5. Permanent saline water bodies were created on former flood prone low beaches. 6. Roads perpendicular to the beaches served as passages for tsunami to travel inland wherever roads touched the beach. 7. A conspicuous heavy mineral rich black sand seam was exposed along several beaches, a unique process provoked by the tsunami. 8. Our observations revealed a red clayey deposit more than 100m inland; gravel, large shells, sand and dead wood was common, at places up to 430m from the swash zone.9.
Our observations and measurements at 25 stations confirm that coastal geomorphic features such as sand dunes and dense casuarina forests played a defensive role in the wake of the tsunami. High dunes with vegetation and with steep seaward gradients neutralised wave up-rush. Assets behind dune complexes remained intact due to the natural buffer protection offered by sand dunes and trees to entire villages.
In comparison, wherever the sea shore was occupied by dense dwellings in place of dunes, the tsunami wave bypassed the flat beach thus razing whatever came its way. All the beach front houses disappeared in totality. Field measurements reveal that only the frontal strip ranging up to 25m were twisted, bent and stripped of leaf cover. The average width of damaged trees equals 14m where the wave run-up was as high as 6.5m above sea level.
Having learnt grave lessons, it was hoped that the tsunami would boost coastal management and hazard policies; this aspiration has not come about. CRZ laws guarantee protection to lowlands susceptible to rise in sea levels due to global warming, but do not reckon wave run-up and flooding due to abnormal transgressions. Despite tsunami experience, India does not have a coastal hazards policy. Multiple factors are responsible for recurring coastal disasters: (a) non-implementation of existing policies, (b) breakdown of enforcement, and (c) lack of post-disaster redevelopment guidelines. A lack of science-policy connection and fragmented policy approaches affects coastal management in India. Hence, the need to devise new regulations, revamp enforcement mechanisms and revise implementation strategies. The rebuilding process does reveal some positive, but mostly negative trends: (a) Although afforestation efforts are laudable, the standards of monitoring and compliance are often inadequate; hence restoration efforts, (b) our policies permit the reconstruction of a smashed structure in the same form and location as before, (c) rebuilding permission is rarely sought, (d) rebuilding projects do not undergo any scrutiny, (e) the scientific community has to decide whether hard protection structures are sufficient, or whether beach restoration is a sustainable alternative.
The inhabitants of coastal Tamil Nadu lost their lives because they were occupying landforms that they were not supposed to alter. The prevailing CRZ laws prohibit indiscriminate use of sea side spaces; sand dunes are fully protected from human interference under the CRZ.
Since CRZ is routinely violated, these constructions lacked designated setback and consistent natural protection. In contrast, coastal vegetation and villages behind dunes and forests remained unharmed. Herbs on the dune, shrubs on hind dune, followed by bushes and trees further inland form a gradation/progression of vegetation and a natural slope. A public policy instrument has to (a) consider options for adaptation against, rather than mitigation of, coastal hazards, and (b) adopt measures for restoration of coastal sand dunes with sufficient forested shelter belts backshore. These strategies offer the most appropriate, long term, sustainable management solutions for Indian coasts.
(Dr Antonio Mascarenhas is a former Scientist, NIO, Goa)