TheAlderney Race is a strait that runs betweenAlderney andCap de la Hague, a cape at the northwestern tip of theCotentin Peninsula inNormandy. A strong current runs through the race north of the Passage de la Déroute, a treacherous passage separating the Cotentin from theChannel Islands. The current is intermittent, varying with the tide, and can run up to about 12knots (22 km/h; 14 mph)[citation needed] during equinoctial tides. The French call itRaz Blanchard.[1] InNorman French it is calledL'Raz.
The Alderney Race is 8nautical miles (15 km; 9.2 mi) across and located roughly between Alderney, in theBailiwick of Guernsey, and La Hague, France. It constitutes the northeastern limit of theGulf of Saint-Malo.
When the wind and the race current flow in opposite directions, the sea becomes particularly chaotic: wave heights can reach 4 metres (13 ft) and have wavelengths smaller than 50 metres (164 ft). The waves break with violence, thus making shipping conditions particularly dangerous.[2] On the contrary, when the wind and the stream flow in the same direction, the sea becomes calm, provided that thetidal coefficient is not too great.
The uneven seabed – both Alderney and La Hague lie in theArmorican Massif – makes the situation more complicated. Bad weather can produce abundant wind-blown foam, making visibility poor. During good weather, opposing wind and currents can cause breaking waves, especially at Banc de la Schôle and at Longis Bay in Alderney.
The power of the current comes from the narrowness of the strait and from the fact that there is a 2-metre (6 ft 7 in) tidal height difference betweenCarteret and La Hague as well as between la Hague andCherbourg.
Because of the enormous potential it sees in tidal power, the French government plans to usetidal turbines to tap the energy of the Race.[3][4]