WATERFRONT STRUCTURES

Figure 1-13.—Rubble-mound breakwater or jetty. Figure 1-14.—Composite breakwater or jetty. WATERFRONT STRUCTURES Waterfront structures may be broadly divided into three types as fpllows: (1) harbor-shelter structures, (2) stable-shoreline structures, and (3) wharfage structures. HARBOR-SHELTER STRUCTURES Harbor-shelter structures are offshore structures that are designed to create a sheltered harbor. Various types of these structures are discussed below. A breakwater is an offshore barrier, erected to break the action of the waves and thereby maintain an area of calm water inside the breakwater. A jetty is a similar structure, except that its main purpose is to direct the current or tidal flow along the line of a selected channel. The simplest type of breakwater or jetty is the rubble-mound (also called rock-mound) type shown in figure 1-13. The width of its cap may vary from 15 to Figure 1-15.—Caisson breakwater or jetty. 70 feet. The width of its base depends on the width of the cap, height of the structure, and the slopes of the inner and outer faces. For a deepwater site or from with an extra-high tide range, a rubble-mound breakwater may be topped with a concrete cap structure, such as shown in figure 1-14. A structure of this type is called a composite breakwater or jetty. In figure 1-14, the cap structure is made of a series of precast concrete 1-8