Training walls and groynes PDF

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Summary

Coastal Geography - Notes look at training walls and use of groynes in managing the CSB and long shore drift...

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Year 11 Geography

Human Impacts The interruption of longshore drift - Training walls Longshore drift: The movement of sediment by currents running parallel to a beach. What is a training wall? Rock and concrete structures that are built at the mouth of rivers to ensure a safe passage for watercraft. The walls extend oceanward.

Picture of training walls

Impact: Sea training walls interrupt longshore drift. Sand will clog up the entrance to the mouth of the river and needs to be dredged to keep the mouth clear. Sand also gets lost offshore as it is pushed out to sea. This results in a loss of sediment to the compartment. In Northern NSW, the Tweed River training walls have caused a huge loss of sediment north of the Tweed and the beaches along the Gold Coast have been losing sand. As a result a very expensive sand bypass pumping operation has been put in place to ensure the sand continues to move northward. This ensures the beaches to the north receive sand.

Groynes What is a groyne? A groyne is a rock or concrete wall built at right angles to the beach to obstruct the drift of sediment or to minimise beach erosion. Picture of a groyne A)

Groynes interrupt long shore drift, but are put in place to try and trap sand on beaches that have problems with erosion (usually due to the loss of dunes). As you can see in photograph A, sand builds up on one side of the groyne and does not allow sand to move along the coast. The side with no sand is called a groyne shadow. Beaches down the coast from the groyne miss out on sand transported by longshore drift. B)...