. Atoll research bulletin. Coral reefs and islands; Marine biology; Marine sciences. 30. Fig 12c : Lagoon circulation generated by a constant 10 m s"l easterly wind at Tikehau. Fig. 12d : Lagoon circulation generated by the connection of the three sources of energy (tide : 10 cm, surf: 0,3 m3 s-l/m and wind : 4 m s-1) at Tikehau. AN EXAMPLE OF MAJOR DISTURBANCE : CYCLONES About four cyclones per century are likely to occur in the Tuamotu archipelago but during the hot season 1982-1983, no less than four cyclones (Orama, Reva, Veena and William) and a tropical storm (Lisa) ravaged French P
. Atoll research bulletin. Coral reefs and islands; Marine biology; Marine sciences. 30. Fig 12c : Lagoon circulation generated by a constant 10 m s"l easterly wind at Tikehau. Fig. 12d : Lagoon circulation generated by the connection of the three sources of energy (tide : 10 cm, surf: 0,3 m3 s-l/m and wind : 4 m s-1) at Tikehau. AN EXAMPLE OF MAJOR DISTURBANCE : CYCLONES About four cyclones per century are likely to occur in the Tuamotu archipelago but during the hot season 1982-1983, no less than four cyclones (Orama, Reva, Veena and William) and a tropical storm (Lisa) ravaged French Polynesia, causing severe damages to human installations, vegetation and coral reef ecosystems. This meteorological phenomenon of an outstanding frequency and intensity induced waves measuring more than 10 meters, a sea- level rising of 3 meters above predicted tidal levels, and a wind blowing in excess of 160 km per hour with gusting to over 200 km per hour. In particular, the cyclone Veena occurred in the vicinity of Tikehau between the 6th and 13th of April 1983. SCUBA Dive surveys carried out on the same transects before and after that disaster allow to assess the magnitude of damage caused to coral communities, and to explain destruction mechanisms. Two years later, SCUBA Dive surveys carried out on the same transects showed that time of recovery is very long. It will take at least five decades to have the coral communities in the state observed prior 1983. Damage assessment Damaged area (SD) is assessed by multiplying the length of destroyed reef (L) by 200 m (this value is the average length / of the outer slope between the depth of 0 and 90 m where hermatypic corals live). L is an estimation based on field observations made during 22 SCUBA Dive surveys around the atoll rim. In Tikehau, an area of 13 million square meters is estimated to have been damaged. This represents 80 % of the outer slope (Laboute, 1985). The area located windward of the atoll (from the north aroun
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