NO. 45 - October 1954 



II-A "Modification of Wave Height Due to Bottom Friction, 



Percolation and Refraction" by C. L. Bretschneider and 

 R. 0. Reid 



A report on a theoretical investigation of the trans- 

 formation (including energy loss) of waves in shallow 

 water by bottom friction, percolation, refraction and 

 shoaling. Using dissipation functions introduced by 

 Putnam and Johnson (1949), derived from the theory of 

 progressive waves of small amplitude, a general 

 solution of the steady state energy equation is 

 obtained. For the case of a bottom of uniform slope 

 and the case of a bottom of constant depth, the 

 solutions are presented in convenient graphical form, 

 making it possible to obtain the reduction factor due 

 to friction or percolation for any bottom slope, 

 depth, initial wave height or period if the friction 

 factor and permeability coefficient for the bottom 

 are known. An example involving refraction is also 

 presented. 



NO. 46 - September 1954 



II-A "Field Investigations of Wave Energy Loss in Shallow. Water 

 Ocean Waves" by C. L. Bretschneider 



Results of a field investigation of loss of wave energy 

 from ocean waves passing through shallow coastal waters 

 in the Gulf of Mexico off the coast of Louisiana and 

 Texas are reported. Results from field observations 

 are compared with existing theoretical treatments for 

 losses due to bottom friction. As apparent friction 

 factors determined appeared to be relatively high, 

 energy losses due to oscillatory adjustment of the 

 bottom to variation in wave pressure caused by the 

 passage of surface waves are also considered. Analysis 

 of recorded wave data for this project are included for 

 comparison with previously published data on statisti- 

 cal distribution of wave heights in ocean wave trains. 



92 



