Seychelles Nation - 29.12.04
Sunday’s (December 26) tidal waves bent around the edges of both Mahe and Praslin to swing inland toward the southern and western areas of the islands at an even greater force than that of its original impact.
Environment principal secretary Rolph Payet said this Tuesday December 28 when describing to reporters at the Botanical Gardens how the tidal waves originated and spread on Sunday, and why much of the coasts on Seychelles’ two biggest islands sustained severe damage.
The tidal waves on Sunday resulted from an earthquake off the northern coast of the Indonesian island of Sumatra, which caused the sea floor to shift 10 metres upwards along a 1,000 km rift.
While 10 metres may not seem like much, Mr Payet said that across such a distance an enormous amount of water was displaced, causing sea water to whip out across the ocean.
And it was only ocean that stood between Sunday’s massive Indonesian earthquake and Seychelles – with no barriers to slow it down the tidal waves spanned more than 4,200 kilometres to cause havoc on Mahe and Praslin in ways few, if any, could have predicted.
The waves moved rapidly from the epicentre, first through Sri Lanka where thousands were killed, then on to the Maldives just a few hours later before hitting Seychelles from the Northeast shortly after mid-day.
Mr Payet said officials were still calculating the force at which the tidal wave hit the local islands, but indicated that an estimate would be released later.
Officials at Tuesday’s press briefing also detailed how the tidal waves “refracted” around Mahe’s southern and western peninsulas – around Takamaka and Port Glaud, respectively.
Acting director of the National Meteorological Services (NMS) Denis Chang-Seng said when the tidal waves refracted around the island, more and more water began to accumulate and rush towards West and South Mahe.
He said this was why areas like Port Glaud, Grand Anse, Anse Boileau and others in the Southwest were severely affected while Anse aux Pins, situated on the east coast but lying parallel to the direction of the tidal wave, was spared from the worst of the disaster.
A similar phenomenon was observed on Praslin, where the tidal wave swept inland at Grand Anse and other areas in the island’s Southwest despite the fact that it was sheltered from any direct impact the wave would have had coming from the Northeast.
“The nature of a wave is determined by the coastline and any barriers there may be,” he said. He noted that large bays like Anse a la Mouche and Anse Boileau are especially vulnerable since more water is able to accumulate and gather strength.
The impact of barriers, however, were more noticeable in Northeast Mahe, where it was confirmed by Mr Payet that the reclaimed islands sitting just off the coast saved much of Ma Constance, Pointe Conan and Ma Joie from major flooding.
Mr Payet said this was especially important because as the wave travelled in between Mahe and Ste Anne it began to change – as the passage narrowed the wave grew higher and thus more dangerous, he explained.
This is the same reason that Victoria was hit as hard as it was, Mr Payet added, noting that the ship channel into the port made for a stronger wave as it pushed through the harbour and into town.
As for North Mahe – which was the first to feel the effects of the tidal wave – it is believed that the large rock formations around Glacis and Northeast Point helped to absorb much of the wave’s impact.
Mr Payet said the outer islands were not as affected because unlike the inner islands, they lie beyond the continental shelf where the impact of the tidal waves were not as severe.
