A forgotten threat called coastal erosion

In 1982, a group of private investors opened the Palm beach Hotel, a sprawling tourism complex by the Atlantic ocean in Benin, a small country on the coast of West Africa. The hotel's picturesque location, a stone’s throw away from the ocean, and its reputation for good food, made it a popular seaside spot. Eight years later, however, Palm Beach was closed down as the waves crept too close for comfort. It has since been totally engulfed by the advancing ocean that is eating away beaches right along Benin's 150 km of coastline and several other beach hotels are under threat. Environmentalists say the building of a new port 40 years ago, the construction of dams on rivers near the coast, the removal of sand from beaches to make cement, and other human activities are partly responsible for the coastline's rapid retreat. According to the government the sea is advancing in some places at a rate of 20 metres a year. Grand Popo, a small town near the western border with Togo, has virtually disappeared into the ocean as a result of the coastline retreating by up to 15 metres a year over a period of several decades. Hundreds of houses there have crumbled into the sea. More seriously, Cotonou, the commercial capital and main port of Benin, is also under attack. The city began to suffer coastal erosion in 1962 after the construction of breakwaters for new deep-water port interrupted the wave-driven movement of sand along the coastline. For the next 25 years the waterfront to the east of the breakwaters, deprived of new sediments to make up for those being washed further down the coast, retreated by 15 to 20 metres a year. That rate has since slowed. Christophe Dah Dehoui, the head of the residents' association in the seaside suburb of Finagnon, said that over the past two years more than 500 houses there had been undermined by the advancing waves. And Antoine Ayivi remembers that when the school was built in the Donaten district of the city in 1978 it was a safe 300 metres from the shoreline. The sea now laps within 20 metres of its walls. Coastal erosion is partly a natural phenonenon, but the United Nations Development Programme (UNDP) and environmentalists believe that human activities are responsible for accelerating the process. One big factor is the removal of sand from beaches for construction purposes. According to Lazare Gnolonfin, a civil engineer and expert on coastal management at the Port of Cotonou, more than one million cubic metres are extracted from Benin's beaches each year. Gnolonfin said water discharges from dams, such as the Nagbeto hydro-electric development, were meanwhile washing out to sea sediments which in the past were deposited along the coast. These particles of sand used to partially replace others that the waves washed away. Gnolonfin said the Nagbeto dam alone had reduced the accumulation of sediments along the coast by 100,000 cubic metres a year. Ominously, he pointed that the dams are here to stay, and there are no readily available substitutes for beach sand in the local construction industry. The government is, however, taking some action to slow down the sea's advance. The ministry of environment, housing and urban development has ranked the fight against coastal erosion a top priority for the next decade. It has begun to build groynes - strong fences buried in the sand at right angles to the sea that slow down the movement of sand by along the beach by ocean currents. However, only a handful of groynes have been installed since the government lacks the money to embark on a large-scale project. According to Marcel Baglo, director of the Benin Environment Agency, the government needs 20 billion CFA (US $ 34 million) to build the required number of groynes along its entire coast. "If you think of the cost of undertaking other infrastructural projects today, particularly the motorway from Cotonou to Porto Novo, it is certainly something worth doing," he said. An additional $42 million would be needed to extend the anti-erosion programme to include other measures. But Environment Minister Luc Gnacadja complains that it is difficult to raise aid money for such projects. "International donors do not yet realise how critical the problem is," he said. "For the moment we are just doing what we can with our own means, consolidating the most exposed areas," the minister said, noting that "the land which disappears into the sea is worth more than four times more than the investment required to save it."