Boris Johnson has proposed a bridge across the English Channel to connect England and France, but apart from the cost and construction, one of the biggest challenges is the weather in the Dover Strait. One problem is wind funnelled through a gap between the hills of the North Downs in England and the Collines de l’Artois in France. Westerly or southwesterly winds speed up as they squeeze through this gap, much the same way that a river flows faster as it passes through a narrow gorge.
This wind gap phenomenon is well known in Wellington, New Zealand. The Cook Strait separating the North and South Islands is surrounded by mountains that funnel winds through the 14-mile-wide strait. That creates a river of wind that tears through “Windy Wellington”, said to be the windiest city in the world with an average of 178 days a year of gale-force winds. The North Island’s strongest recorded gust of 154mph was measured in 1962 on a hill just a few miles from the city centre.
A suspension bridge spanning the Dover Strait would also have to be very high to give shipping enough clearance. The towers holding supporting pylons and cables for the bridge might need to be more than 500m tall. That complicates how to deal with the wind, as Wanda Lewis, a structural engineer at the University of Warwick, pointed out on The Conversation website. “As the wind hits the pylons and cables, it causes them to vibrate,” she wrote. “In some instances, this can grow into a phenomenon known as ‘flutter’, causing the entire structure to become unstable, as happened to the Tacoma Bridge, which collapsed in 1940.” The supporting cables would have to be exceptionally strong and light, possibly made of a stronger material than anything used before.
Perhaps the most sobering lesson comes from the 19th-century Dutch artist Louis Meijer. His painting Storm in the Strait of Dover shows sailing ships tossed around in a gale, battling to stay afloat.
