286 mason. SHORE-CONTROL PROBLEMS [Ch. 15 



If in addition information on the direction of approach to the shore 

 of the waves is available, it is possible to formulate a time distribution 

 of wave energy with respect to direction of application of the energy. 



From the engineer's point of view the adequate solution of shore- 

 control problems is contingent on accurate knowledge of the following 

 factors: (1) the sources and character of the beach material; (2) the 

 rates of supply and loss of material to and from the problem area; 

 (3) the manner of movement of material from the source to the beach 

 and from the beach to other areas. 



It is immediately apparent that, if answers to these questions can 

 be obtained, the physical conditions that cause the problem situation 

 will be defined. This is the definition of the problem. It has been 

 the experience of investigators in this field that there are usually 

 unique definitions of the problems; each problem is separate and dis- 

 tinct, thus making the solution of such problems by analogy an un- 

 satisfactory method. There has been a tendency to practice solution 

 by analogy, which still continues to some extent but which is on the 

 decline as more and more knowledge of the problem is developed. 



The physiographic unit is of value in determining the source and 

 character of the beach material, particularly if the surficial geology 

 of the area has been adequately studied. The material-energy balance 

 of the unit, and specifically of that portion of the unit requiring con- 

 trol, greatly facilitates the consideration of the last two factors. 



Frequently the definition of the physical conditions at the site by 

 consideration and study of the above factors will suggest the type, and 

 sometimes the detail, of the control to be employed. However, to 

 arrive at a rigorous engineering solution the problem is analyzed 

 further. 



The analysis reduces to consideration of the following factors: 

 (1) the feasible methods of modifying rates of supply and loss of 

 material to achieve the desired results, and the effects of such modifica- 

 tion; (2) the design requirements of the feasible methods of modify- 

 ing supply and loss rates; (3) the economic cost of each of the feasible 

 methods of modifying rates of supply and loss. 



COLLABORATION BETWEEN GEOLOGISTS AND ENGINEERS 



Geology can help engineering in connection with all but the last 

 factor, but it must, to be of maximum value, focus attention on the 

 dynamic aspects and significance of its findings. The average engineer 

 who needs the information has little, if any, means of translating clas- 

 sical geologic information into a form he can use. A geologist in- 



