Coasts and their management

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Emanuel Hausmann Geography: Coasts and their Management 03/01/2009

Coasts and their Management

Factors Affecting The Shoreline Environment

The coast is a narrow zone that is especially active in the shaping of landforms. In the coastal zone the sea, land and air all meet together and interact to shape the landforms, which are in turn heavily influenced by human activity also. The shoreline (Küste) is the actual boundary (Grenze) of the land and sea. However, when we study coasts, we usually look a little more widely than the shoreline. Coastal terrains extend inland as far as the seawater, salt spray or wind-blown sand extends. They extend seawards to the depth of wave base, which means the depth to which waves can more sediment on the sea bed.

It follows from this that the width of a coastal terrain in one area may be very different from its width somewhere else. The coastal terrain may be only a few tens of metres wide on steep, rocky coasts, but it could be tens or hundreds of kilometres wide where estuaries move sea water far inland or where there are wide shallow continental shelves. On the high energy coastlines of southern Australia, the wave base may be 20 metres below sea level, but on the low energy coastlines common in Western Europe, the wave base may be only a few metres below sea level.

With the exception of some glacial processes, all the processes that form landforms anywhere in the world operate on coastal terrains. In addition, there are many unique processes that operate in coastal terrains. The in inputs and outputs used to describe fluvial landforms (Flusslandschaften) could also be applied to the shoreline environment. The processes acting on coasts are mostly marine (meerartig) or atmospheric, (zur Luft gehörend) although other important processes include the work of chemical and biological factors.

Marine Processes

Marine Processes are the action of waves, tides (Gezeiten) and currents (Strömungen) – these supply most of the energy that shapes landforms in the coastal zone. The original sources of energy that drive marine processes are solar radiation (Sonnenstrahlung) and the gravitational pull of the sun and moon.

The superficial undulations (Wellenformen) of the water surface produced by the wind blowing over the ocean are called wind waves. Small circular movements in the wind produce minor (unbedeutende) undulations in the water surface, and some of these are reinforced (verstärkt) by subsequent gusts of wind (nachfolgenden Böen). The stronger the wind, the larger the waves will be. Although wind waves are highly visible to someone standing on the shoreline, they are not waves that perform most of the work of landform formation.

Larger waves are formed by a wind that blows for a long time or which has a long fetch (the distance over which the wind blows, Windlauflänge). When these larger wind waves leave the area where they were formed and begin to travel freely, they become more even and longer crested (crest=Kamm), and become known as swell (Dünung). These waves are considerable (bedeutend) potential to shape landforms on the shoreline.

It is possible to measure waves, and this helps us to distinguish between constructive or deconstructive waves. Many of the measurements focus on the crests, or tops of the waves, and the troughs, or dips between them. Some of the important measures commonly used are the following:

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Wave height (H) is the vertical distance between a crest and its adjoining through (nachbar Talsohle).

Wave length (L) is the horizontal distance between two successive (aufeinanderfolgenden) crests.

Wave period (T) is the time taken for two successive crest to pass a fixed point.

Wave velocity (V) is the speed of wave crests.

Wave steepness (H/L) is the ratio of wave height and wave length.

Wave steepness cannot exceed a ratio of 1:7, or 0.14, because at that point the wave breaks. It is possible to calculate the wave length if the wave period is known. This can be done using the ...

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