Difference between revisions of "Dune erosion"
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Revision as of 20:35, 14 November 2007
Dune erosion involves that, during a severe storm, sediments from the mainland and upper parts of the beach are eroded and settled at deeper water within a short time period; this is a typical cross-shore sediment transport process.
Often a storm is accompanied with much higher water levels at sea than usual (storm surge) and also much higher waves do occur.
While under ordinary conditions the shape of a cross-shore profile might be considered to be in accordance with these normal conditions ('dynamic equilibrium' shape), under storm (surge) conditions the initial shape before the storm can be considered to be far out of the equilibrium shape which belongs to the severe storm conditions. Profile re-shaping processes will occur, causing erosion of sediments from the mainland and the settlement of these sediments at deeper water again (see Fig.2). Notice in Fig.2 that the control volume does not change by the storm surge processes.
Although this dune erosion process will cause loss of mainland, to a first approximation no loss of sediments out of the cross-section occurs; only a redistribution of sediments over the cross-shore profile takes place during the storm.
Of course depending on the characteristics of the storm, erosion rates of several metres per event (say per day) have to be considered. These episodic events do occur along all types of coasts (along structural eroding, stable and even along accreting coasts).
After the storm generally a recovery towards the original situation will occur due to the processes under normal conditions.
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