Nourishment addresses a sediment deficit – the cause of erosion – by introducing large quantities of beach material to the nearshore system. Much like a bank account, when more material is added than removed, a build-up occurs and the shore builds seaward conversely, when more material is removed than deposited, erosion occurs (Morton, 2004). The term ‘sediment budget’ is used to describe the careful balance which exists between incoming and outgoing sediment.
This is achieved by introducing large quantities of beach material to the coastal sediment budget from an external sediment source, also referred to as a borrow site. The logic behind beach nourishment is to turn an eroding, reflective beach into a wider, dissipative beach, which increases wave energy attenuation (French, 2001).Īs well as helping to dissipate incoming wave energy, beach nourishment addresses a sediment deficit: the underlying cause of erosion. A ‘dissipative’ beach – one that dissipates considerable wave energy – is wide and shallow while a ‘reflective’ beach – one that reflects incoming wave energy seawards – is steep and narrow and achieves little wave energy attenuation. The cross-sectional shape of a beach therefore affects its ability to attenuate wave energy. Different beach profile shapes and gradients interact with waves to differing extent. The benefit of beach nourishment comes from wave energy dissipation when waves run up a beach and break, they lose energy. Nourishment is often used in conjunction with artificial dune creation.
The aim, however, should be to ensure that nourishment material is compatible with the existing natural (or native) beach material (Reeve et al., 2004). This approach is mainly used on sandy beaches but the term can also refer to nourishment with shingle or even cobbles. The description of this technology originates from Linham and Nicholls (2010).Īddition of beach material rebuilds and maintains the beach at a width which helps provide storm protection. Nourishment can also be referred to as beach recharge, beach fill, replenishment, re-nourishment and beach feeding. It is a soft engineering approach to coastal protection which involves the artificial addition of sediment of suitable quality to a beach area that has a sediment deficit. Beach nourishment is an adaptation technology primarily used in response to shoreline erosion, although flood reduction benefits may also occur.
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