Ch. 15] REFERENCES 289 



There is some justification for thorough study of the details of 

 selective transportation of shore material, with particular reference 

 to the disposition of material. Closely related to this problem is the 

 question of thickness of beach and near-shore deposits and their 

 stratification as indicators of the past history of the beach. 



In these suggested research problems as well as in others, the useful- 

 ness of tracers having the same dynamic characteristics as the mate- 

 rials under study is apparent. There is some evidence that adequate 

 knowledge of the petrography of shore and source materials would 

 make possible the use of some fractions of the native materials as 

 tracers, thus greatly simplifying some of the technical phases of the 

 studies. 



It must be apparent that there are great deficiencies in our knowl- 

 edge of even some of the less complicated phenomena of shore-line 

 behavior. It is believed that future developments in shore study and 

 control are contingent principally on fundamental research in mate- 

 rials, the transportation of materials, and methods of modifying the 

 material-energy balance of an area. In the field we are concerned 

 with, as in many other technical fields, there is presently a serious, 

 almost critical shortage of basic information. Without such informa- 

 tion, the technical man finds it impossible to advance applied research. 

 In this field engineers have progressed as far as they have mainly on 

 fundamental research in other fields, notably geology, hydraulics, 

 mathematics, and physics. Our greatest need is for work on shore 

 materials and the transportation of materials under maritime condi- 

 tions. Available knowledge of unidirectional transportation of mate- 

 rial in streams is of only partial value to us in our problem of multi- 

 directional flow under periodically varying forces. We must know 

 more about the details of material derivation from source rocks, the 

 degradational processes of derivation and transportation, the possibili- 

 ties of metamorphosis of constituent particles and populations of 

 particles. It is essential to know the details of littoral movement of 

 materials, the relationships of energy to material movement, the fea- 

 tures of energy transfer and dissipation in the coastal environment, 

 the requirements for modification of the material-energy balance, and 

 even how to compute an accurate, quantitative material-energy bal- 

 ance. 



REFERENCES 



Bagnold, R. A. (1946). Motion of waves in shallow water — interaction between 

 waves and sand bottoms: Proc. Roy Soc. London, ser. A, vol. 187, pp. 1-18, 

 Oct. 1946. 



