File:Shore processes and shoreline development (1919) (14577497827).jpg

Identifier: shoreprocessessh00john (find matches)
Title: Shore processes and shoreline development
Year: 1919 (1910s)
Authors: Johnson, Douglas Wilson, 1878-1944
Subjects: Shorelines Coasts
Publisher: New York : John Wiley & Sons, Inc. (etc., etc.)
Contributing Library: University of California Libraries
Digitizing Sponsor: MSN

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neously travelling seaward ^, A further reason for the landward progress of coarse debrisduring wave action is elaborated by Cornish in his book on Waves of the Sea and Other Water Waves ^ He shows thatthe forward current begins just as the vertical component ofwave motion is raising coarse material from the bottom, withthe result that this material is readily carried forward while insuspension; whereas the backward current sets in while thewater particles are descending in their orbits and are thereforedepositing coarse material upon the bottom where it is lesseffectively moved. This argument loses much of its force be-cause Cornish takes no account of the fact that on a smoothbottom the oscillatory motion of the water particles is backwardand forward in a horizontal plane, the vertical currents uponwhich the validity of his theory depends being absent. Im-mediately above the bottom the vertical element of the oscil-lation begins to appear, and material carried upward a sufficient y.
Text Appearing After Image:
WAVE CURRENTS 93 distance by eddies due to inequalities of the bottom might besomewliat affected in the manner described. If we turn our attention for a moment to the action of normalwaves of translation, we have to note that the currents whichthey produce constitute essentially one intermittent currentacting in a uniform direction. The water particles, from thesurface to the bottom, move forward and then stop, the processbeing repeated with the passing of every such wave. Accord-ingly the debris on the bottom is always urged forward; andsince these waves usually come on-shore, they give rise to alandward progress of all movable material, both fine and coarse.Russell attributes the shoreward transportation of shingle andwreck to the action of waves of translation^°. It appears cer-tain that either waves of translation or oscillatory waves may,under proper conditions, effect a very remarkable transportof debris toward the land; for Murray has shown that shingleand chalk ballast droppe

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