Scientists Assess Tsunami Damage

Studies of environmental damage left behind by the massive December 2004 tsunami find widespread destruction in India, both above and below ground. The Tamil Nadu coast was among the regions most severely affected. Its shoreline was pushed back by 20 metres (65 feet), and flooding reached as far as 862 m inland.

The tsunami demolished many of the homes located within 40 m of coastal sand dunes. In some places the damage extended to buildings 132 m from shore.

Built-up areas of Tamil Nadu where forests had been cleared received the heaviest damage. Intact casuarinas forests dissipated the energy of the giant ocean waves enough to curtail the devastation. Damage to beachfront forests typically extended 14 m inland and no trees farther than 25 m from shore were uprooted.

Another heavily hit area, the Vellar estuary on India's southeast coast, was extensively rearranged by the tsunami waves that reached it. The wall of water generated by the Dec. 26, 2004 earthquake near Indonesia was up to four metres high when it hit land at Vellar and flowed two kilometres (1.2 miles) inland.

Sand dunes along the Vellar coast that used to tower six metres were scooped away by the tsunami and dumped into the inlet, creating a huge tidal flat that now interferes with boat passage. Losing its sand dunes leaves the estuary more vulnerable to the ravages of severe storms. Scientists anticipate it could take a decade for the dunes to reform.

The tsunami also left its mark on farmland and fresh water. It contaminated soil and ground water in agricultural areas of coastal Nagapattinam district with salt. While soil was returning to normal conditions after six months, the water still remained too saline for drinking and irrigation.

Deteriorated ground water was also found on Neill Island in the Andaman Islands lying east of India. The tsunami introduced seawater into the aquifer, but the earthquake itself left long-lasting impacts on the island's water supply. Movement from the quake produced cracks in the limestone rock containing the aquifer. These cracks opened the aquifer to intrusion from seawater, allowing salt water to quickly flow in and taint the freshwater.

References

H. Chandrasekharan, A. Sarangi, M. Nagarajan, V.P. Singh, D.U.M. Rao, P. Stalin, K. Natarajan, B. Chandrasekaran and S. Anbazhagan. 2008. Variability of soil–water quality due to Tsunami-2004 in the coastal belt of Nagapattinam district, Tamilnadu. Journal of Environmental Management.

S. Jaya Kumar, K.A. Naik, M.V. Ramanamurthy, D. Ilangovan, R. Gowthaman and B.K. Jena. 2008. Post-tsunami changes in the littoral environment along the southeast coast of India. Journal of Environmental Management.

Antonio Mascarenhas and Seelam Jayakumar. 2008. An environmental perspective of the post-tsunami scenario along the coast of Tamil Nadu, India: Role of sand dunes and forests. Journal of Environmental Management.

Y. Pari, M.V. Ramana Murthy, S. Jaya kumar, B.R. Subramanian and S. Ramachandran. 2008. Morphological changes at Vellar estuary, India—Impact of the December 2004 tsunami. Journal of Environmental Management.

V.S. Singh. 2008. Impact of the Earthquake and Tsunami of December 26, 2004, on the groundwater regime at Neill Island (south Andaman). Journal of Environmental Management.

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