As waves approach the shore they begin to pick up and carry sand at a depth of approximately half their wave length. This produces an Offshore Bar.  Conintued periods of slight seaas and swell waves move the Bar onshore.

 

When it reaches shore the Bar, low intensity waves carry sand up and onto the Berm before sinking into it and depositing the sand they are carrying.  At low tide onshore breezes can also move sand onshore.

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If there is another season of low intensity waves, the Berm may be left onshore and another built infront of it.

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On the Australian coast spinifex grass will grow out to the Berm. Its leaves begin to trap wind blown sand and its roots form a mat to slow erosion by waves during storms.  As it survives other plants like Pigface will grow on it and trap more sand. The Berm will grow to become a Foredune.

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Over time the dunes are covered by forest. 

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