[Coral-List] impact of beach rock on erosion

Barbara Gratzer barbaragratzer at gmail.com
Sat Aug 9 05:06:19 EDT 2014

Dear Coral-Listers, 

My question is not directly related to corals, however I hope there are some people out there who can share their experience, opinion and expertise.

Maldives are well known to suffer from tremendous erosion problems over the past few years. Natural reasons are natural shifts (up to several metres per year), mass bleaching events, the tsunami in 2004, who probably allocated huge sandmasses, thereby influencing under currents throughout the Atolls, and loss of natural vegetation such as sand stabilising trees. 

I am working in a resort in Baa Atoll where we are trying to identify other mechanisms that influence beach erosion. Our aim is to use as natural techniques as possible to keep sand shifts to a minimum. It was suggested that beach rock, which has eroded over the past 20 years and now is about 15 - 20 metres away from the shoreline, additionally adds to beach erosion. 
We assume: Since a wave brakes when the wave hight is less than half of the wave length, the waves are crashing on the beach rock rather than on the beach, thereby creating high turbulence in between the rock and the actual shoreline where waves would naturally brake. We further assume this turbulence creates larger sand shift movements. We are wondering if beach rock, once exposed, should be removed and natural walls such as coral walls should be enhanced on the crest instead. 

Is there any available literature about currents near beaches, turbulences on the reef flat or impacts of exposed beach rock on currents? 

I am looking forward to receiving your answers and thank you in advance!


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