. Detached breakwaters for shore protection. Breakwaters; Shore protection. PART II: GENERAL OPERATION OF DETACHED BREAKWATERS 6. As previously mentioned, detached breakwaters protect a zone of the beach from direct wave action and transform the incoming waves. The area immediately behind the breakwater is sheltered because wave energy is dissi- pated on or reflected off of the structure. Wave energy is also reduced as waves diffract around the breakwater ends, resulting in a lateral spread of wave energy and a reduction in energy reaching the shore at any given point. The net effect is to red
. Detached breakwaters for shore protection. Breakwaters; Shore protection. PART II: GENERAL OPERATION OF DETACHED BREAKWATERS 6. As previously mentioned, detached breakwaters protect a zone of the beach from direct wave action and transform the incoming waves. The area immediately behind the breakwater is sheltered because wave energy is dissi- pated on or reflected off of the structure. Wave energy is also reduced as waves diffract around the breakwater ends, resulting in a lateral spread of wave energy and a reduction in energy reaching the shore at any given point. The net effect is to reduce the capacity of waves to entrain and transport sediment in the breakwater shadow and to drive sand into the sheltered area immediately behind the breakwater where it is deposited, thus causing a bulge or salient to develop along the shore (Figure 2). Littoral drift entering the breakwater zone of influence may be permanently trapped or removed at a later date when transport conditions change. If wave conditions are relatively con- stant, a state of dynamic equilibrium may be attained. AVERAGE LONGSHORE COMPONENT OF WAVE ENERGY (PLUS DIRECTION) PREDOMINANT WAVE DIRECTION AND MAGNITUDE \ AVERAGE LONGSHORE COMPONENT OF WAVE ENERGY (MINUS DIRECTION) / WAVE DIFFRACTION PATTERNS UPDRIFT AND DOWNDRIFT SHORELINE IMPACTS BREAKWATER HEIGHT AND POROSITY'. 3 ACCRETED SHORELINE LITTORAL TRANSPORT RATE Figure 2. Segmented detached breakwater design considerations 7. The functioning of a detached breakwater is best understood by comparison with a more traditional sand-accreting shoreline structure, the groin. Both groins and detached breakwaters are methods of beach erosion control which can involve the use of a single structure or a group of structures designed as a system. Groins are generally built perpendicular to shore, while detached breakwaters are generally built parallel to the shore. Groins do not appreciably reduce the wave energy striking the shore and they. Please note that t
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