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Title: Environmental impact assessment report for the proposed housereef protection measures Chaaya Reef Ellaidhoo, North Ari Atoll, Maldives
Authors: Sandcays
Keywords: Mobilization
Material transport
Pollution control and waste minimization
Health and safety
Marine water quality
Bathymetry and ocean currents
Condition of the reef
Issue Date: Jan-2011
Citation: Sandcays. (2011). Environmental impact assessment report for the proposed housereef protection measures Chaaya Reef Ellaidhoo, North Ari Atoll, Maldives. Male': Maldives
Abstract: This report addresses the environmental concerns of the proposed immediate measures for the protection of South-West corner of the Chaaya Reef Ellaidhoo, located at eastern rim of the North Ari Atoll. In addition to immediate measures, long term monitoring, planning and mitigation has also been incorporated into the project. Chaaya Reef Ellaidhoo is 300 m long and 280 wide with a total land area at 55,626 m2 covered with common vegetation found in Maldives. The total built up area is recorded at 7,060 m2 (12.7% of total land area). The house reef of Ellaidhoo is considered to be one of the famous and attractive dive spots in Maldives. The island is one of the first resorts in the Maldives and has several coastal developments including offshore breakwaters, seawalls, jetties and water bungalows. There is no beach around the island except south west corner of the island and small isolated patches of beach. The beach formation at south-west corner of the island is severely transformed into tombolos and salients due to the several coastal structures present, including the harbour being located on this side. Consequently, almost every bit of sand on the beaches of Ellaidhoo has accreted in this area over the years, especially during the Northeast monsoon of each year, which is the peak tourist season, resulting in the loss of sand from the island beach system through openings in the offshore breakwater made of cement/concrete and coral rubble. Almost every diver complains about the heavy down pour of sand from this area, which happens to be the area in which the Dive School is located. They say it is like a raining of snowing with sand down there. Therefore, the Dive School, has been hoping for a solution to this growing concern and it is in a dire situation needing an immediate solution along with a long term management strategy. The proposed project is targeted to improve this serious situation. The proposed project involves two basic steps: first to remove or recycle the sand that has accumulated in the area over the past several years and then to correct the tombolo/salient formation and outflow of sand into reef flat at seaward side of the existing segmented offshore breakwaters at south-west corner of the island. Since a lot of sand has been deposited and the rate of accretion is high, manual removal of sand would not be useful. A machine-based approach is necessary and two such approaches have been proposed: one is to use sand pump and the other is to use an excavator to pump or move (recycle) the sand to another location. The sand pump is preferable given that the resort is operational resort and closing the area would not be possible as the area is the primary public area of the resort. If an excavator were to be used, the sand moving has to be done at night without disturbing the guests, which would be quite challenging. Therefore, the primary option is to use a sand pump in the location to recycle the sand. Although improving the offshore breakwaters in the area to minimize tombolo formation is the next step it is not any less important than the first step of moving the sand. For this, it is proposed to cut off sections of some of the longer breakwater barricades to improve flow and completely cut off the tombolos. However, this may mean that the sand will flow further towards the harbour area where sand will accumulate and find its way onto the reef again through the long breakwater in the harbour. Therefore, it would be necessary to ensure that sand removed from this area is recycled in such a way that the sand does not accrete only in this area. Therefore, retention structures such as headlands or groynes would be required in areas where the recycled sand would be placed. This will form the third most important component of the project. An estimated volume of about 4,500m3 of sand will be removed from the tombolos formed in the lee of the breakwaters at south-west corner of the island which will be used to nourish the eroded shoreline around the island, as the sand is part of the sand budget moving around the island. In order to create stable beaches in nourished areas, it may be necessary to remove the existing seawalls which tend to wash away the sand with the reflection of waves off its surface. The reef top just behind the offshore breakwaters is found not healthy with sand spits, rubbles and dead corals. However, the reef slope or edge of the reef is found with rich composition of fish communities and live corals. In the south west reef zone surveyed indicated with 30% of rubbles, 18% of dead corals and 14% sand cover. Live corals including Acropora digigate and Acropora Tabulae are at 9% and 13% respectively. At south east zone more than 40% found with dead corals and 28% of coral algae with 16% of live coral cover indicate the reef top is not healthy. At eastern zone the reef was found with 66% dead corals along with 18% coral algae. At north east reef zone 39% dead corals along with 34% of live corals were found including digitates and tabulae corals. Compared to reef areas surveyed south east reef zone found healthier compared to other sites. Sand cover is highest at south-west and south zone of the reef. The tombolo/salient formation and resultant sand flow onto the reef at south-west corner as discussed is the main issue that has been highlighted and also indicated by aerial photography and the results of the surveys. In order to carry out an in-depth examination of the situation of sand cover at seaward side of existing offshore breakwaters at south-west corner, an open dive was made by a certified diver in the EIA survey team along with a diver from Chaaya Reef Ellaidhoo. Approximately 18m deep dive to reef slope behind the breakwaters / jetty at south west corner of the island was made during data collection. The overall environmental impacts of the project have been assessed using appropriate matrices and the results indicated that the proposed project had net positive impact. Given that the project has major socio-economic and more importantly environmental benefits, it is recommended to allow the project to proceed as proposed. Environmental monitoring recommended for the project includes the monitoring of the shorelines and beach at project site before, during and after the proposed improvements and continuous monitoring of the shoreline and long shore as well as offshore currents around the island and bathymetry in the area. Annual monitoring reports have to be submitted to the Environmental Protection Agency during the monitoring period.
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