AN EXPERIMENTAL STUDY OF SUBMARINE SAND BARS 



Section I. INTRODUCTION 



Submarine sand bars are frequently found as characteristic features 

 of ocean and lake beaches. The bars may occur singly or in series 

 and are usually associated with sand beaches and offshore areas. 

 An individual bar formation consists of a crest or ridge to seaward 

 and a trough or depression, to shoreward. A series of bars is a number 

 of related crests and troughs. These bar formations have been 

 studied by geographers and geologists, and the literature on the 

 subject has a history of almost three quarters of a century. The 

 earliest descriptions of these underwater formations were those of 

 the German investigator Hagen, whose work appeared in 1863 

 (reference 1) and was followed by that of Otto, Lehmann, Hartnack, 

 and Evans (references 2, 3, 4, and 5) among others. Although 

 considerable data on the material aspects (form, dimensions, and 

 number) of bars is thus available, almost no authoritative information 

 on the mechanism of bar formation and movement has been obtained. 



Admittedly the formation and migration of oflFshore sand bars are 

 hydrodynamical phenomena of a complex nature difficult to study 

 in a natural environment; under these circumstances laboratory 

 experimentation can prove of considerable value. Economy of time, 

 the limitations of available apparatus, and the natm^e of the problem 

 require that the general case be resolved into components. Each 

 component can then be considered individually as involving only a 

 limited number of variables. The present investigation concerns, as 

 a first step, the metrical aspects of bars; i. e., the shape and disposition 

 of bars, as they are influenced by the size characteristics of waves. 



This paper reports the results of experiments made to determine 

 the existence of basic relationships governing bar phenomena. Ob- 

 servations were made of the form, dimensions, and number of bars; 

 wave characteristics; ripple formation; and nature and volume of 

 sand movement involved in bar phenomena. During the investigation 

 certain qualitative observations on some of the factors affecting the 

 mechanism of bar formation and movement were made. Although 

 these qualitative observations are limited, they will be discussed 

 briefly because of their implications for further study. 



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