analyzed. Additional tests have been performed to delineate the effect 

 of temperature on the amount of sand in suspension, confirming earlier 

 results that the suspended amount is materially increased for colder 

 water. 



(f) Wave Forecasting 



Utilizing additional observed data, slight revisions to previously 

 developed forecasting curves have been presented at the 6th Coastal 

 Engineering Conference in a report entitled "Revisions in Wave Fore- 

 casting: Deep and Shallow Water". Work has been continued on the 

 development of the joint distribution for heights and lengths, and heights 

 and periods. Using the general form of a theoretical joint distribution, 

 a derivation may be given for a family of theoretical energy spectra. 

 These spectra are to be compared with those previously proposed by others. 

 Methods for predicting waves under hurricane conditions have been derived 

 and are reported on in an article entitled "Hurricane Design Wave Prac- 

 tices" published by the American Society of Civil Engineers. 



(g) Equilibrium Profile Tests 



Tests made in the prototype tank involving waves up to 5-1/2 feet 

 in height were also tested in small wave tanks at scales of 1 to 10 and 

 1 to 15, utilizing the same sand material. These tests indicate, as 

 suspected, that cin appreciable scale effect exists. The critical steep- 

 ness value of .02 to .025, which has been found in small scale tests to 

 delineate the capability of waves to erode or accrete material on a beach, 

 was found not to apply in the larger scale tests, with steepness as low 

 as .005 still eroding a beach with an initial 1 on 15 slope. Lower den- 

 sity material is now being obtained for tests in small scale tanks to 

 attempt to determine the criteria for scale reproduction. It is thought 

 that this may be on a settling velocity ratio. 



(h) Hurricane Studies 



The staff of the Board has continued to support the present hurricane 

 study program of the Corps of Engineers. Considerable work has been done 

 by the staff in developing and improving simplified methods for estimat- 

 ing storm surge elevations and wave heights under a variety of shoreline 

 conditions. Wave forces, wave run-up and wave overtopping phenomena 

 connected with seawall, dike, and barrier design under hurricane conditions 

 have also been studied. Studies have indicated that a wave set-up exists 

 in areas of strong wave attack, and that this increase in water elevation 

 due only to the action of the waves may amount to as much as 3 feet with 

 incident waves of 25 to 30 feet in height. This set-up effect appears 

 also to be dependent on slope, with the set-up being highest for rela- 

 tively gentle beach slopes. Tests with 1 on 3 and 1 on 6 levee slopes 

 with an offshore 1 on 10 slope have revealed a zero or even small nega- 

 tive set-up where 25 and 30 foot waves on offshore 1 on 70 slopes have 

 shown positive set-ups as high as 3 feet. 



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