Coastal engineering is the discipline which deals with these problems. To 

 do this, the coastal engineer must not only design a solution but also have 

 knowledge of the natural processes at work, the wind and water forces driving 

 them, and the probable impact of the solution on the existing coastal system 

 and environment. Coastal engineering is a very site-specific discipline, and 

 solutions successful at one point may not work at another. 



To achieve the objectives of coastal engineering, practitioners must 

 utilize several disciplines. From field investigations and a knowledge of 

 physics, they develop an understanding of the coastal processes at the project 

 site. Then using models, both physical and numerical, they study the possible 

 solutions and their impacts. However, no factor is more important for the 

 engineer than past experience. Monitoring of constructed projects provides 

 tremendous assistance towards planning the next. 



The coastal engineer's work is divided into three phases: understanding 

 the nearshore physical system and the shoreline's response to it; designing 

 coastal works to meet project objectives within the bounds of acceptable 

 coastal impact; and overseeing the construction of coastal works and 

 monitoring their performance to ensure that projects function as planned. 



III. THE BEACH AND NEARSHORE SYSTEM 



The beach and nearshore zone of a coast is the region where the forces of 

 the sea react against the land. The physical system within this region is 

 composed primarily of the motion of the sea, which supplies energy to the 

 system, and the shore, which absorbs this energy. Because the shoreline is 

 the intersection of the air, land, and water, the physical interactions which 

 occur in this region are unique, very complex, and difficult to fully under- 

 stand. As a consequence, a large part of the understanding of the beach and 

 nearshore physical system is simply descriptive in nature. 



1. The Sea. 



Water covers 71 percent of the Earth, and thus a large part of the Sun's 

 radiant energy that is not reflected back into space is absorbed by the water 

 of the oceans. This absorbed energy warms the water, which in turn warms the 

 air above the oceans, and forms air currents caused by differences in air tem- 

 perature. These air currents blow across the water, returning some energy to 

 the water by generating wind waves. The waves then travel across the oceans 

 until they reach land where their remaining energy is expended on the shore. 

 The power in the waves as they arrive in the nearshore zone can vary from 1.39 

 megawatts per kilometer (3,000 horsepower per mile) of beach on a relatively 

 calm day (0.6-meter or 2-foot waves) to 25 times this amount or more during a 

 storm. 



The motions of the sea which contribute to the beach and nearshore physical 

 system include waves, tides, currents, storm surges, and tsunamis. Wind waves 

 are by far the largest contribution of energy from the sea to the beach and 

 nearshore physical system. As winds blow over the water, waves are generated 

 in a variety of sizes from ripples to large ocean waves as high as 30 meters 

 (100 feet) (see Fig. 1-2). 



1-4 



