Offshore breakwaters are therefore placed as far away from the surf-zone as possible and they are as short as possible to minimize the impact on coastal morphology. to minimize the impact on the coastline.Offshore breakwaters are normally located at a slightly greater water depth than is required for navigation, thus avoiding/minimizing capital dredging and minimizing sedimentation. In order to minimize the works and to avoid the associated impact, an offshore breakwater may be the answer. At such locations, a traditional port would have to extend far from the shoreline or extensive dredging works would have to be carried out to provide access to the port. The offshore breakwater is often used when the slope of the coastal profile is small. The purpose of an offshore breakwater is normally to protect an offshore ship wharf against wave action, which means that an offshore breakwater is a special type of port, as illustrated in Fig.3. Offshore breakwaters are located far outside the surf zone, x^*\gt 3, see Fig.1. Sand accumulation forming a salient in the shoreline behind an offshore detached breakwater, connected to the coast by a bridge Sergipe, Brazil x^*=3.6. L_G Length of gap between breakwaters in a segmented breakwaterįig.3.If there are several breakwaters in a series, this is referred to as a segmented breakwater, where the length of the gap between the breakwaters is denoted: But again, parameters other than the breakwater length and distance influence the accumulation pattern. 0.9 to 1.0, the sand accumulation behind the breakwater will connect the beach to the breakwater in a tombolo formation. Tombolo: When the dimensionless breakwater length L_B^* is greater than approx.However, parameters other than the breakwater length and distance also influence the accumulation pattern. 0.6 to 0.7, a bell-shaped salient in the shoreline will form in the lee of the breakwater. Salient: When the dimensionless breakwater length L_B^* is less than approx.x_ěreakwater distance relative to surf-zone width.The first type is generally used as ship berth, whereas the latter two types of breakwaters are mainly used for shoreline management.Ī detached emerged breakwater can be characterized by the following parameters (Fig.2): There are three different types of breakwaters, schematically indicated in Fig.1.: These characteristics of a breakwater are utilised in different ways for various types of breakwaters by varying relevant parameters. Through this shelter, to manipulate the littoral transport conditions and thereby to trap some sandĪ detached breakwater provides shelter from the waves, whereby the littoral transport behind the breakwater is decreased and the transport pattern adjacent to the breakwater is modified.Distance from shoreline and location relative to the surf zoneĪ shoreline management breakwater serves two purposes:.The following characteristics determine the impact on the shoreline: Ī special type of detached breakwaters is dealt with in the article Artificial reefs.īreakwater schemes have many variables. Most of the content of this article is drawn from Mangor et al. Different aspects of breakwaters as coastal protection are discussed, as well as their impacts on shoreline evolution. This article provides a general introduction of detached breakwaters and describes emerged breakwaters, submerged or low-crested breakwaters, floating breakwaters and other special type breakwaters. Several types of breakwaters exist, from which detached breakwaters are the most common type. In general terms, a detached breakwater is a coast-parallel structure located inside or close to the surf-zone. 6.2 Disadvantages of submerged/low crested breakwaterĭetached breakwaters aim to protect a coast or activities along the coastline (e.g.6.1 Reasons for selecting a submerged/low breakwater.5 Segmented emerged detached breakwaters.4.3 Optimization of the breakwater design.
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