The initial cost of the harbor, including protective structures, channels, basins, docks, 

 and administrative and service facilities, must be consistent with: (a) achievement of 

 reasonably long-lived construction, (b) avoidance of components with unusually high 

 maintenance requirements, and (c) provision of an esthetically pleasing and functional 

 installation. 



Conversely, the harbor design, types of materials used, and workmanship involved in the 

 initial construction should be of a quaUty no higher than is necessary to reduce maintenance 

 to the minimum level possible without overspending to achieve slight advantages in 

 maintenance reduction. 



The overall harbor area must be adequate for all purposes, with a proper balance between 

 land and water area. Enough perimeter land must be available for streets and parking, for 

 ancillary facilities that produce the revenues needed to supplement slip rental fees, and for 

 all harbor support facilities. Where future expansion is anticipated, adequate undeveloped 

 land or water area must be available and reserved for this purpose. 



A master plan should be adopted as a guide for all future developments. 

 2. Design Criteria for Protective Features and Entrances. 



a. Breakwaters. Where site selection .and environmental considerations indicate a 

 breakwater to be necessary, the type of construction and design will depend on availability 

 and cost of materials, and on the amplitude of the waves to be resisted. The most common 

 type of breakwater used in the open ocean and most large lakes is the rubble-mound 

 breakwater, sometimes armored with concrete units of various shapes (Fig. 18). This 

 breakwater is intended to prevent or reduce the transmission of wave energy into the harbor 

 by absorbing some of this energy and by reflecting as much of the remaining energy as 

 possible back toward the main water body. Design criteria for this type of breakwater can 

 be found in the Shore Protection Manual (U.S. Army, Corps of Engineers, Coastal 

 Engineering Research Center, 1973), and Quinn (1972). If a rubble breakwater is too porous, 

 it will allow transmission of a high percentage of the longer period wave energy through it, 

 and excessive wave disturbance will occur within the interior channels and berthing areas. 

 Under this condition the orbital motion within the advancing wave is destroyed at the 

 breakwater, but the potential energy is transmitted by hydrostatic pressure differentials 

 through the voids in the stonework and a new wave of the same period is generated in the 

 lee of the structure. For this reason, voids in rubble mounds should be reduced by 

 incorporating a low porosity or impermeable core built to as high an elevation as possible in 

 the structure. 



A breakwater is seldom built to a height that will not be overtopped by the design wave. 

 A certain amount of overtopping can usually be tolerated, but only to the extent that 

 regenerated waves causes only minor acceptable disturbance in the protected area. For 

 example, if an open water area such as an entrance channel or main fairway lies immediately 

 behind the breakwater, overtopping waves can usually be tolerated up to the point that the 



47 



