WAVE EFFECT ON THE COAST FORMATION AND EROSION

Walenty Jarocki

Abstract


Various authors explain differently the mechanism of action of waves on the_ sediment movement. Some authors consider that the waves are raising the soil fractions from the bottom and water currents transfer them along the seaboard. The other authors suppose that each wave shears some soil in the bottom in littoral zone of the waves and wind is oblique to the shoreline. Beach currents catch and transport the sediment particles along the seaboard. These authors suppose when the wind is in the direction of seaboard /from sea/ then the bottom currents move in the opposite direction. These currents transport the ground particles in the direction of sea and thus the seaboard erosion arises. When the wind direction is opposite, the botto currents arise in the direction of seaboard and they cause the transportation of ground and the accumulation of seaboards. These reasons show that the action of waves would cause only the separation of ground particles and their asoeading. Our last investigations and observations of the sediment movement have led the conclusion that the waves may cause the raise of the sediment partciles and also their transport. The character of this transport depends on the wave kind and on the height and length of waves. General quantity of the lifted particles by means of waves increases as the power of waves or height and length of waves increases. If the power of waves decreases these particles fall. The waves are able to transport the bed load and detritus load without cooperation of the water current in spite of horizontal or inclined bottom. Under the action of waves the sediment moves the oscillatory movement. The waves move the bed load in the shallow exterior zones with the horizontal bottom only, towards the wave propagation. This material may be moved perpendicular the slope, according to the wave direction or in the opposite on< If the approaching wave creates the acute angle to the shoreline then the bed load moves near the seaboard. The transport of the bed load and of detritus loai change if the water current and waves appear simultaneously. The water current acts generally on the detritus load because the water moves this material easier than the bed load which rolls on the bottom.

Keywords


sediment/wave interaction; sediment movement; littoral zone

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