THEORETICAL FORMS OF SHORELINES

[摘要] In previous publications Pelnard-Considere, Bruun and larras have d.erived theoretical shore formations. When doing so, it is necessary to idealize the conditions, such as a lxttoral transport by waves only, unvarying wave characteristics and a simple relation between the angle of wave approach and the littoral transport. Moreover various other simplifications have to be made in order to make it possible to handle the equations.The question may arise whether results, obtained from such an idealized situation, have any value for practical cases, where the conditions are much more complex and variable. The answer is no when we expect to obtain a true and detailed picture of the development of any particular stretch of coast. Such theoretical exercises can be of real value, however, because they help us to understand why and how certain formations come into being and how they are influenced by certain physical processes* This is the case for instance with such formations as deltas, spits and tombolos.We cannot say that we really know the function which determines the littoral transport. Up to now one of the simplifications in the mathematical treatment has been the restriction to stay within an area in which the values of <*. are so small that the transport may be assaned to increase in direct proportion to the increase of the value of o< ( c< being defined as the angle between the wave direction and the direction of the normal on the coast in the point considered)* However, experiments indicate that the littoral transport very likely reaches a maximum for a wave angle between 45° and 600. Interesting phenomena are bound to occur when this maximum is approached. With this in mind we have tried to introduce a transport function T « A sin 2ex., having its maximum when oC « 45°.

[学科分类] 建筑学

[关键词] shoreline formation;delta;spit;tombolo