A FORMULA 

 FOR THE CALCULATION OF THE TIDAL 

 DISCHARGE THROUGH AN INLET 



Dr. Gar bis H« Keulegan, National Hydraulic Laboratory^ 

 National Bureau of Standards , and Jay Vo Hall, Jr c , 

 Chief, Field Research Section 5 Beach Erosion Bsard 



INTRODUCTION 



During the course of an investigation of Santa Rosa Island, Florida, a 

 number of engineering problems arose which required special study because of 

 the lack of field data„ The most interesting of these problems involved the 

 advisability of cutting an inlet through the island „ The specific problem, 

 which required special mathematical treatment, was brought about through the 

 determination of the division of flow between Pensacola Inlet and the rela- 

 tively small cut through Santa Rosa Island „ Inasmuch as adequate field data 

 were available in the vicinity of the proposed cut, this locality presented 

 no problem o However, the only information available for Pensacola Inlet was 

 the tidal prism of Pensacola bay. With this tidal prism quantity in mind as 

 the only available working data, certain basic assumptions were made and a 

 formula was derived for the determination of the maximum discharge that 

 could be expected through the inlet at any tidal cycle „ Since the formula 

 as derived checked remarkably well when applied to a number of inlets that 

 had been gaged, it was thought that the information would be of value to 

 engineers „ Hence it is presented in this monograph as a matter of record „ 

 In the following pages there is a complete mathematical analysis of the 

 Droblem including the basic assumptions, the development of the formula, the 

 test cases as applied to four inlets on the Atlantic coast, the development 

 of a correction factor introduced to adjust the basic assumptions, and a 

 demonstration of the practical application of the formula „ 



MATHEMATICAL TREAT-TENT OF PRO & EM 



The following mathematical analysis presents the development of the 

 equations used for the computation of the maximum quantity (discharge) of 

 water which may be expecte d thr ough a tidal inlet at any tidal cycle „ 



