|Initial Rapid Assessment of Tsunami Damage to Coral Reefs in Eastern Sri Lanka
Initial Rapid Assessment of Tsunami Damage
to Coral Reefs in Eastern Sri Lanka
2-5 March 2005
CORDIO Coral Reef Degradation in the Indian Ocean
IUCN The World Conservation Union
List of Participants / Authors
Marten Meynell IUCN
Mattias Rust CORDIO
Frontpage: Mattias Rust
Pasikudah: Mattias Rust
Palchenai: Marten Meynell
Sallithievu: Mattias Rust
Initial Rapid Assessment of Tsunami Damage to Coral Reefs in Eastern Sri Lanka
This report was produced jointly by IUCN* and CORDIO*
* CORDIO/IUCN Regional Marine Programme, 53 Horton Place, Colombo 7, Sri Lanka
Five marine sites were surveyed in the Ampara and Batticaloa districts on the east coast of Sri Lanka. One site was a shipwreck, two were patch reefs and two were shallow fringing reefs. These sites have not been scientifically surveyed for many years, if ever, due to the military conflict between the Liberation Tigers of Tamil Eelam (LTTE) and the Sri Lankan Government. Therefore, there was no baseline information to compare the results with. The tsunami impact seems to vary across the sites, ranging from high intensity levels at one site to no visible impact at another. Smothering by sediments appears to have occurred on some sites, predominantly on the shallower, fringing reefs. On the inshore sides of the fringing reefs there were extensive beds of dead coral rubble, which was where the majority of the smothering was observed. Broken coral pieces were found amongst the rubble and were consequently being abraded by their interaction with the waves and rubble. On some sites there were small amounts of debris, predominantly organic terrestrial, like logs and branches. There were no seagrass or seaweed beds present at any of the sites. Severe beach erosion had occurred at all sites, with some beaches suffering over 50% loss of beach width and up to one meter loss in height. An attempt to survey the reef at Pasikudah Bay, where there was existing environmental baseline information, was aborted due to the possibility of there being primed anti-personnel land mines in the marine environment as a result of the receding tsunami waves. Detailed mapping and long-term monitoring are needed on the sites to establish true reef conditions and coverage. Marine mine clearance is needed at Pasikudah to ensure the safety of future surveyors.
IUCN (The World Conservation Union) Sri Lanka country office, supported by CORDIO (Coral Reef Degradation in the Indian Ocean) and IUCN’s Regional Marine Programme, conducted a scoping mission to the east coast of Sri Lanka. The purpose was to conduct rapid damage assessments concerning terrestrial, marine, and livelihood issues in response to the tsunami.
The scoping mission took place 2-5 March and covered several parts of the coastline in the Ampara and Batticaloa districts. A tight schedule, the inability of independent transport, and safety issues arising from live ammunition having been washed out of an army camp by the tsunami, compromised the time at, and the number of, marine sites surveyed.
Additionally, as no previous surveys had been carried out on the reefs in question, there was no baseline information available to compare the results against. Consequently, the marine assessments must be seen as initial general surveys of the extent and condition of the reefs, combined with rapid assessments on the likely impact of the tsunami on the coral reefs.
A document “Tsunami Damage to Coral Reefs – Guidelines for Rapid Assessment and Monitoring” was prepared for IRCI and ISRS by a contact group comprising of the GRCMN, CORDIO, Reefbase Reefcheck and IUCN networks and individual scientists. This was the principal document used to help coordinate the marine assessments carried out by IUCN and CORDIO on the east coast of Sri Lanka.
The reason for not using SCUBA was the logistical problems involved in conducting surveys in areas that are in the territory of the Liberation Tigers of Tamil Eelam (LTTE), and that have also suffered considerable infrastructure damage resulting from the tsunami.
Due to the above constraints, the guidelines were adapted to allow a very rapid and general survey of the reef layouts and conditions. Notes and observations were collected in order to assess:
· the damage suffered by the coastline and human settlements,
· the location and depth of each reef,
· the condition and extent of the corals,
· whether there was clear evidence of tsunami damage to the reefs,
· whether there had been any debris deposition on the reefs.
At Kalmunaia, human settlements had been located very close to the sea, and have consequently suffered considerable damage. According to the villagers the highest tsunami wave was about 10 meters. The beach, which has a post-tsunami width of 20m, is not littered with significant amounts of debris.
Marine surveys were carried out in three locations.
The first survey was on a substantial shipwreck c.600m from the shore. The metal wreck appears to be fragmented, with a total length of about 50m. It lies on a sandy seabed at a depth of c.12m, and the top of the bow extends to just over 2m below the surface. The boat’s surface is covered in algal turf and barnacles, some of which have been recently ripped off. There are also occasional branching coral colonies which are in good condition but small in size, less than 50cm in diameter and are presently growing in an upright position, implying that the wreck itself has not been overturned or moved significantly during the tsunami. Visibility during the survey was 8m.
Two sites was surveyed at roughly 1000 and 1300m from the shore and at a depth of 10m. The seabed is sandy and the coral cover is very patchy. The coral, which is in good condition and covers 10-20% of the seabed, is dominated by massive, encrusting and table coral colonies. There are no areas of seagrass or seaweed, but occasional sponges or hydrozoans can be found. Overall tsunami damage appeared to be minimal; there are few broken corals, no significant piles of rubble or new sedimentation. However, a small number of large (1m diameter) coral colonies were observed to have been overturned. The site closer to land had more rubble of branching and foliaceous corals on the seabed. The visibility was 15m.
At Pasikudah the tsunami had caused extensive damage to the coast and human settlements in the area. The army base camp at Pasikudah was flooded by the tsunami, which washed much of the stored ammunition out of the camp. There were also mine fields in the area which have been affected. The mines and ammunition have been deposited over the surrounding land, and consequently the army is combing the area to retrieve them. Everything from artillery grenades to anti-personnel mines is being found in large quantities on a daily basis.
The reef at Pasikudah was originally the main focus for the marine team during the field trip due to the fact that the reef was extensive and baseline information was also available. However, no under-water survey was conducted because the possibility of un-recovered primed mines in the marine environment.
The beach, which was previously a famous and prosperous tourist destination, has suffered severe erosion; there has been a decrease in beach height of about 1m and width of c.100m and was now only up to 15m wide. Large piles of coral rubble had been accumulating on the beach since the tsunami. These piles consist of a variety of coral types, the majority of which are branching corals in small broken pieces. Close to the army base, there are aggregations of dead, but larger colonies of massive and table coral colonies. These dead corals range in appearance with some looking far more recently dead than others but the majority of the corals appeared to have been dead pre-tsunami. This correlates with an earlier report (Dharmaretnam, M. & Ahamed, R., in prep) that observed moderate amounts of dead coral rubble, predominantly on the western side of the reef.
The village of Palchenai, at the north end of the bay, has been severely damaged by the tsunami. The height of the greatest tsunami wave at this location was 5 meters. The beach is covered in organic debris in the form of tree trunks, branches, and leaf litter. There are also some signs of human rubbish but this is not extensive. The beach width is now 50m, having been 100m before the tsunami. There seems to have been additional beach erosion on c. 1m in height, estimated from the height of the base of the palm trees nearest the water’s edge.
The reef at Palchenai is situated at the southern point of the 2 km long bay, 150 meters from the shore. It is roughly 200m long and 10 to 20m wide. It is a shallow fringing reef; the inshore side of which is in less than 1m of water, and the outer edge has a depth of 3m. The visibility was 2-5 meters.
The dominant forms of coral on the reef are branching, table and massive colonies. There are also some foliaceous and encrusting corals present. The percentage of live coral cover ranges from 5% on the shallower inshore edge to c.30% on the deeper outer edge. There is very little, or no, presence of sponges, soft corals, anemones, hydrozoans, sea grasses or seaweed.
On the shallower inshore parts of the reef there are piles of rubble, mostly made of dead branching coral covered in algal turf and sediment. Many pieces of branching coral have been broken and are now being abraded amongst the rubble. There were also occasional observations of table corals and massive coral colonies having been overturned.
The live coral, however, is in fairly good condition and has not suffered significantly from the tsunami. Smothering has occurred in some areas but not extensively. There is some debris on the reef in the form of small branches and there are no signs of man-made debris or litter.
Sallithievu – Money Island
Sallithievu is a sandy island located roughly 100m off the coast of Challitivumunai. The island itself is c.75 meters long, parallel to the beach, and some 15 meters wide at the broadest part.
The mainland beach varies in width from 10 meters up to around 75 meters and has lost approximately half a meter in height due to the tsunami. The beach width does not seem to have decreased but was at the time of the survey covered with quite a lot of organic debris and some elements of man-made litter such as plastic bags. Palm trees grow adjacent to the beach. According to a local source, the wave was about 10 meters high. The infrastructure in the area, which is presently in an LTTE-controlled area, is poor.
The parts of the coral reefs surveyed lies to the south and east of the island. The depth on the site varied between 1 and 3 meters with a visibility of 2-5 meters. Due to the shallow water and unprotected location, the wave-action was considerable. The seafloor around the island and its reef is sandy, without sea grass or seaweeds.
To the south and southwest of Sallithievu the seafloor is dominated by beds of coral rubble, mainly from branching corals, covered with a thick layer of algal turf and sediment. Very occasional patches (<50cm diameter) of living coral were found in this area, and these are showing clear signs of stress due to smothering.
Located east of Sallithievu is a fringing reef, forming a U-shape around the island, with branching, massive, tabular, foliaceous and encrusting coral forms dominating. Branching corals and foliaceous colonies in particular, bear obvious marks of physical damage and the seafloor around the reef is covered with rubble, mostly from branching corals, covered by a layer of algal turf. Occasionally there are big colonies of massive and table corals, with a diameter of 80 cm and less, turned over. There is very little, or no, presence of sponges, soft corals, anemones, hydrozoans. As the reef itself stands up from the seafloor1-2 meters, the surviving corals are not subject to further damage from movement in the surrounding rubble beds. The waves breaking on top of the reef keep it fairly clean from sediment, but closer to the seafloor smothering occurs. Live coral cover is best on the outer edges of the reef, peaking at some 15-20%. There is no debris on the reef crest itself, but occasionally amongst the rubble, organic debris such as branches and tree trunks can be found.
Table 1 describes the level of mechanical damage suffered by each reef as a result of the tsunami. It also shows the level of sediment smothering and the amount of debris deposited on the reefs by the receding waves.
Recommendations and Needs
· As the reefs discussed above have not been previously surveyed, detailed mapping and establishment of long-term monitoring sites are required. Due to the extent of the area in Kalmunaia, initial mapping would be best carried out using the manta tow method.
· Since there is little debris accumulation, urgent reef clean-ups are not necessary.
Dharmaretnam, M and Ahamed, R (in prep) A preliminary baseline survey of the coral reefs of Passikuda, CORDIO project and status report 2004.
GCRMN/CORDIO/Reefbase/ReefCheck (2005) Tsunami Damage to Coral Reefs – Guidelines for Rapid Assessment and Monitoring (Working Draft – January 2005) ICRI/ISRS. Web link: http://www.iucn.org/info_and_news/press/coral-reef-guidelines-draft1.doc
Rajasuriya, A., (2002) Status Report on the Condition of Reef Habitats in Sri Lanka, 2002. In: Linden, O., Souther, D., Wilhelmsson, D., Obura, D. Coral Reef Degradation in the Indian Ocean status report 2002, pp. 139-148.