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the shoreline adjus ment behind a segmented breakwater that is permeable and overtopped. d. Segmented Breakwaters. A segmented breakwater offers a very func- tional solution for a long section of shoreline that requires wave transmis- sion to prevent tombolo formation. The structure can be built nearshore in an economical water depth because it permits a constant proportion of wave energy into the protected area. Also, the diffracted waves have the same period as the incident waves. Segffiented breakwaters can be designed to allow the beach in their lee to accrete enough sediment to provide an erodible buffer during storms and still maintain the natural longshore transport rate during normal wave conditions. The amount of :energy reaching the lee of the structure is controlled by the width of the gaps between the breakwaters and the wave diffraction through these gaps. The gaps should be at least two wavelengths wide, and the length of each structure segment should be less than the distance offshore. Provid- ing fewer gaps of greater width will cause the shoreline to respond with spaced bulges and embayments with an enlarged relief (the seaward distance from the more shoreward point of the embayment to the tip of the cuspate spit}, which does not provide uniform storm protection along the project. If this is not acceptable, increasing the number of gaps and shortening the length of each segment will promote features of less relief, providing more uniform protection. Segmented offshore breakwaters are illustrated in Figures 5-30, 5-32, and 5-33. Figure 5-33 illustrates the use of offshore breakwaters in conjunction with. a beach fill. e. Positioning with Respect to Breaker Zone. Placing the breakwater landward of the nrsrmal breaker zone will advance the shoreline and may cause tombolo formation (see Fig. 5-32). If positioned well shoreward of the breaker zone, a large percentage of the total longshore transport will pass seaward of-the structure and the effect on the adjacent shoreline will be less severe. This method is not recommended for coasts with steep beach slopes and narrow surf zones because the area shoreward of the breakwater will tend to fill completely, turning the breakwater into a seawall. f. Structure :Orientation. fihe orientation of the breakwater with respect to both the predominant wave direction and the original shoreline can have a marked effect on ffhe size and shape of the resulting cuspate spit or tombolo. A change in structure orientation modifies the diffraction pattern at the shoreline, and subsequently, the shore response. An approximation of the shape of the shore response when waves are normally incident to the shoreline can be deteroained by using the procedures discussed in Chapter 2, Section IV to determine the diffracted wave crest configuration. For waves that are extremely oblique to the shoreline, it is recommended that the breakwater be oriented parallel to the incoming wave crests. This will provide protection to a longer section of shoreline for a given structure length; however, it will probably increase the amount of construction material required for the structure since one end of the breakwater will be in water deeper than if it were oriented parallel to the bottom contours. 6. Other Considerations. Apart from shore response, there are several other factors which affect 5-71