Wave-Action and Shore-Lines

Abstract

AN article by Mr. W. V. Lewis on the “Evolution of Shore-line Curves” (Proc. Qeol. Ass., 49, Pt. 2; 1938) is a valuable contribution to a well-worn subject. The author's position is fundamentally that of Sir Henry de la Beche, founder of the Geological Survey, who a hundred years ago stressed the importance both of the longshore drift of material by prevalent waves and the independent action of storm or dominant waves in piling up embankments of detritus in the direction of the greatest force, sometimes at right angles to the shore. In later years opinions changed, and explanation of the evolution of coastal outline was purely on the action of longshore and eddy currents. Latterly, however, there has been a revival of the wave-action hypothesis due largely to the findings of the Boyal Commission on Coast Erosion and Afforestation and the work of Steers, Johnson, and others. Mr. Lewis proceeds to examine in detail various sections of coastline in Britain on the Moray Firth, Cardigan Bay, Bristol Channel, Isle of Purbeck and Chesil Bank, and suggests that shore curves, far from being explicable only by reference to longshore currents, yield in certain cases readily to analysis in terms of the direction of approach of both dominant and prevalent waves, especially the former.