February 13, 1979 Tsunami: SW Great Britain, United Kingdom

Reference #14268:

A series of long-period waves arrived unexpectedly in southwest Britain on the morning of Tuesday, 13 February 1979. The waves entered the Bristol and English Channels, and also occurred along the Atlantic seaboard of Europe as far south as Portugal. Laurence Draper and T. M. Bownass briefly reported the damage inflicted by the waves in southern Britain (1983), including the Isles of Scilly, Plymouth Harbour and Sound (where a wave broke over the 19-meter-high breakwater light), Seaton, Portland, Tenby in South Wales, Christchurch Bay (2-meter wave heights), and even as far east as Hayling Island near Portsmouth (1.5-meter wave height). They also stated that a wave recorder offshore of Lisbon recorded a maximum wave height of 17.2 meters at 3:40 a.m. on 13 February. The arrival of the waves in the English Channel coincided with a surge of 0.6 meters at Plymouth, probably associated with an area of low pressure over the western Channel at the time, and with high tide at Portland at 7:40 a.m. It was here that the most dramatic overtopping of the 12-meter-high eastern end of Chesil Beach occurred, enhanced by refraction and wave set-up, inundating the village of Chesil (Chiswell) with water and gravel.

Draper and Bownass examined the origin of the waves and showed that the local wind was a lo-knots (5 meters per second) easterly and not able to produce the affects observed (1983). They concluded that a deep (9pmillibar) depression in the Atlantic Ocean generated the waves. During the preceding forty-eight hours the depression had “moved with roughly the same speed (30 kn [15 m/sec]) and in the same direction as that of the wave components of about 18-20 seconds [period; c. 500-625 m wavelength} which it had generated, and so continued to input energy preferentially into this longer-period part of the wave spectrum for a considerable time, creating high and unusually-long-period sea waves” (p. 348). Then, “after the source depression died out[,] the waves continued to travel across the ocean at a speed of about 15 m/s” (7. M. Walker i991,66). In addition, the wave train appears to have contained an even longer-period wave set, because the tide gauge of St. Mary’s on the Scilly Isles for that morning indicated “considerable disturbances,” with a wave period of approximately ten minutes (Draper and Bownass 1983,349).

Reference #14269:

On the morning of the 13 February 1979, a series of waves hit the southwest coast of the UK. Waves also struck mainland Europe as far south as the coast of Portugal, and as far north as Tenby in South Wales. Haslett and Bryant (2009) references Draper and Bownass (1983) describing the pressure profile over the Atlantic Ocean, which started with a deep depression, that moved with roughly the same speed (30 kn [15 ms−1]) and the same direction as that of the wave components. These, however, given the type of weather system, were more likely long period swell waves.