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Assessment of TSUNAMI DAMAGE in the Indian Ocean; First Report

First preliminary report of the damage to coral reefs and related ecosystems of the western and central Indian Ocean caused by the tsunami of December 26

The following is a compilation of observations made by experts in the CORDIO/IUCN network in Sri Lanka, India, Maldives, Seychelles and Kenya during the first 10 days following the tsunami. Detailed assessments have been possible in a few areas, while in others very large quantities of suspended solids and detritus in the water and logistical problems (lack of vehicles and damaged roads) have prevented work in the field. Preliminary results are presented below and will be updated regularly.

In Sri Lanka, the quantities of silt and detritus in the water was enormous and has so far prevented attempts to measure the impacts of the tsunami on the reefs. A preliminary field visit by CORDIO/IUCN Sri Lanka and the National Aquatic Research and Resources Development Agency (NARA) on the 7th of January confirmed conditions were improving sufficiently and surveys along the most affected areas on the west and south coasts will start on the 10th of January, focusing on areas where monitoring sites have already been established and baseline data exists. Additional surveys, including the eastern parts of the country, will be conducted where logistically possible. It is estimated that 80 to 95% of the fishing fleet was destroyed in the coastal provinces affected. Many casualties and major damage to infrastructure were reported from a number of coastal areas, including Rekawa in southern Sri Lanka, where CORDIO has been active in providing alternative livelihoods for coral miners.

The places along the coast that were most affected by the tsunami were those that have been disturbed by anthropogenic activities while those that remained intact were less perturbed. For example, mangroves and vegetated coastal dunes seem to have dissipated energy of the wave and provided protection to coastlines, coastal inhabitants and infrastructure. Remote sensing data would be useful to illustrate this as well as study the impacts of the tsunami region wide, and both NOAA and NASA have offered their assistance in this regard. Another purpose of the studies to be carried out during the next couple of weeks will be to try to relate the state of damage on land to the coral mining activities along the coast. The planned studies may provide an opportunity to demonstrate the importance of appropriate planning and opportunity to rebuild villages in a fashion more suited to the environmental situation.

In India, around the islands in the Gulf of Mannar, a rapid assessment has been initiated by the Suganthi Devadason Marine Research Institute - Reef Research Team (SDMRI-RRT) a week after the tsunami to assess the status of corals and associated shallow water habitats. One site each near the islands of Kariyachalli and Vaan in the Tuticorin group and one patch reef site near the mainland were assessed. The results of surveys conducted at the island sites revealed that there was very little damage to coral reefs and associated habitats caused by the recent tsunami. Some colonies of Acropora cytherea had been toppled over and a number of colonies of Acropora intermedia exhibited broken branches resulting from the strong waves during tsunami. However, the damage affected only 1-2% of the branching corals in this area. Although there was no sand deposition on the branching and massive corals, the gravel sand seafloor near the reef area has been covered by a layer of fine sand approximately 1 cm thick. Considerable amounts of seagrass were washed ashore but the meadows adjacent to the reef sites remained intact.
The patch reef site near the mainland is also relatively intact although cup-shaped colonies of Turbinaria sp., which comprise between 25-30% of the live coral cover, are filled with fine sand to a depth of about 4-5 cm. Owing to their morphology, this sand is not likely to be washed out and may cause some mortality among these corals. Fish populations at each site were relatively unaffected. The rapid assessment is continuing for other island areas (Vembar, Kilakarai and Mandapam groups) in Gulf of Mannar and will be completed in a week time. Damage to fishing boats and other equipment was reported from villages along Tuticorin Coast where CORDIO projects are being implemented, as well as from other parts of Gulf of Mannar.

In Maldives, the Marine Research Centre reported that most damage occurred on the eastern side of the atolls in the central section. The tsunami washed over many islands entirely, destroying houses and leaving some trenches. Although some impacts were reported in the Northern Section, no damage was recorded south of the One and a half degree channel. It seems that the impacts of the tsunami in Maldives were tempered by the fact that these atolls are situated in very deep water without a shallow shelf. As a result, the tsunami did not build up into a tall breaking wave, but instead it simply washed over many of the small islands. Some rubble was washed ashore on many islands but no significant boulders have been reported. The water within the atolls appear murky, but outside them it seems rather normal. Potentially the most significant impact is the contamination of the freshwater lens beneath several of the islands with sea water. This is the only source of drinking water for inhabitants and, as a result, potentially severe consequences are expected.

In the Seychelles, soil deposited by the backwash of the tsunami and subsequent heavy rains has ensured that the water has remained extremely turbid and considerable sediment is being deposited on adjacent reefs. A preliminary survey was conducted by the The Seychelles Centre for Marine Research and Technology – Marine Parks Authority of 4 sites on the east and north-eastern coast of Mahe on the 30th of December 2004. The results show that the number of colonies damaged at each site ranged between 1% at Grand Rocher, which is almost entirely dominated by soft corals, and 27% at Anse Cimetiere. The variation in damage between sites is largely attributable to the stability of the reef substrate. At sites such as Moyenne and the Airport, which are founded on consolidated limestone, and Grand Rocher, which is granite, only 10% of colonies or less exhibited damaged. At Anse Cimetiere, where the substrate is unconsolidated rubble, the heavy waves were able to shift the substrate easily causing considerable abrasion and damage to corals. The tsunami reduced the coral cover at this site from 25% to less than 5%. Additional surveys will conducted focusing particularly on sites that are loosely consolidated such as those found at Ile Therese and the island of St. Pierre in the Curieuse Marine National Park. Sites along the north-west coast of Mahe will also be surveyed as there are reports from dive operators that some corals have been damaged on these reefs. Considerable amounts of debris have been caught in the mangroves. Some sea grass beds have been damaged but not extensively. Fishing boats have suffered severely and the freezing facilities and ice making facilities have been destroyed. The harbour has also suffered considerable damage.

In East Africa, the tsunami appears to have been largest in Somalia, where considerable terrestrial damage and many deaths were reported, and smaller towards the south as far as Dar es Salaam. Reports from CORDIO East Africa indicate that no physical damage was caused to the fringing reef in southern Kenya and northern Tanzania, the coastline or other marine habitats, largely because the tsunami reached the coast during mid-tide. In Kiunga, northern Kenya, receding waters exposed subtidal seagrass beds and reef flats, but further south, water levels did not vary beyond extreme low and high tide levels. The most severe impacts were reported from the exposed shorelines of Dar es Salaam, Tanzania, and Malindi, Kenya, where rough conditions associated with the waves caused several drownings in the former, and boat damage in the latter. To date, no damage to coral reefs has been noted at any locations.

CORDIO and IUCN have mobilised their network of scientists and institutions throughout the western and central Indian Ocean to assess the damage to coastal environments caused by the tsunami. Information from CORDIO/IUCN Sri Lanka, the National Aquatic Research and Resources Development Agency (NARA), (others in Sri Lanka), the Suganthi Devadason Marine Research Institute (SDMRI),(Others in India, particularly the Andaman and Nicobar Is), Marine Research Centre, SEAMARC (Other in Maldives), Seychelles Centre for Marine Research and Technology – Marine Parks Authority (SCMRT-MPA), (others in Seychelles), CORDIO East Africa, National Environment Management Authority of Kenya, Kenya Wildlife Service, (others in Kenya and Tanzania) will be reported on the CORDIO ( and the IUCN web sites (

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