Figure 1-13.—Rubble-mound breakwater or jetty.Figure 1-14.—Composite breakwater or jetty.WATERFRONT STRUCTURESWaterfront structures may be broadly divided intothree types as fpllows: (1) harbor-shelter structures,(2) stable-shoreline structures, and (3) wharfagestructures.HARBOR-SHELTER STRUCTURESHarbor-shelter structures are offshore structuresthat are designed to create a sheltered harbor. Varioustypes of these structures are discussed below.A breakwater is an offshore barrier, erected tobreak the action of the waves and thereby maintain anarea of calm water inside the breakwater. A jetty is asimilar structure, except that its main purpose is to directthe current or tidal flow along the line of a selectedchannel.The simplest type of breakwater or jetty is therubble-mound (also called rock-mound) type shown infigure 1-13. The width of its cap may vary from 15 toFigure 1-15.—Caisson breakwater or jetty.70 feet. The width of its base depends on the width ofthe cap, height of the structure, and the slopes of theinner and outer faces. For a deepwater site or fromwith an extra-high tide range, a rubble-moundbreakwater may be topped with a concrete cap structure,such as shown in figure 1-14. A structure of this type iscalled a composite breakwater or jetty. In figure 1-14,the cap structure is made of a series of precast concrete1-8
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