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Beach management
Published in David R. Green, Jeffrey L. Payne, Marine and Coastal Resource Management, 2017
The design of a successful beach management strategy builds on the understanding developed through the site evaluation. The first stage in the design process is most often an options assessment or feasibility study, which, these days, usually utilizes numerical models developed during the site evaluation phase, although it can be based on a detailed understanding of the site. For example, if the cause of erosion is the loss of sediment across-shore during local storm conditions (i.e. steep, short periods causing the offshore transport of sand), then mechanisms to reduce cross-shore sediment transport, such as detached breakwaters or submerged reefs (USACE, 2002; Pilarczyk, 2003), are more likely to be part of a successful beach management strategy than mechanisms which reduce alongshore sediment transport such as groynes. The converse is true where the cause of sand loss is predominantly due to chronic alongshore sediment transport during ‘normal’ conditions.
Marine action and control
Published in F.G. Bell, Geological Hazards, 1999
The groyne is the most frequently used structure to stabilize or increase the width of a beach by arresting longshore drift (Fig. 7.16). Groynes are used to limit the movement of beach material, and to stabilize the foreshore by encouraging accretion. However, groynes do not usually halt all drift. Groynes should be constructed transverse to the mean direction of the breaking crest of storm waves, which usually means that they should be approximately at right angles to the coastline. Standard types usually slope at about the same angle as the beach. With abundant longshore drift and relatively mild storm conditions almost any type of groyne appears satisfactory, but when the longshore drift is lean, the choice is much more difficult.
Contributions of coastal megacities to environmental changes at regional and global scales
Published in Mark Pelling, Sophie Blackburn, Megacities and the Coast, 2014
The geographical position of maritime megacities restricts the expansion-coalescence phases of urban development (Dietzel et al., 2005) from broadly concentric expansion possible for more continental cities. Expansion occurs inland but also particularly along the coast, further degrading these coastal habitats (Costanza, 1997; MEA, 2005). Further habitat degradation occurs due to the construction of coastal or estuarine flood defence walls, groynes and docks, which destroy habitat and can increase physical stresses on biota (Francis et al., 2008; Chapman and Underwood, 2011), and the appropriation of coastal areas for aquaculture and fisheries (Folke, 1998).
Novel method for groyne erosion stability evaluation
Published in Marine Georesources & Geotechnology, 2018
Yajun Wang, Feng Jin, Chuhan Zhang, Jinting Wang, Yu Hu, Jun Wang
The main function of the groyne structure is to divert some natural flow away from the coast so as to safeguard the downstream seashore and coastal engineering structures from erosion and scour. The mechanism of circumfluence surrounding the groyne structure and the deformation of the coastline are shown in Figure 3. Meanwhile, the groyne can break the nearshore flow and then dissipate most of its energy. According to the data in different times in Figure 4, the establishment of the groyne structures can abate efficiently the nearshore flow scour.