T.M. No. 42 (Continued) 



of the operation of such a fixed plant and to relate the volume of 

 sand reaching the pump intake to the wave energy reaching adjacent 

 shores. Field work included measurement of volume of material by- 

 passed by the plant, recording of wave height, period and direction, 

 measurement of alongshore currents, and procurement of sand samples. 

 An empirical relationship between the rate of nearshore littoral 

 movement and the shallow-water wave energy is developed. 



T.M. No. 43 - December 1955 



On Ocean Wave Spectra and a New Method of Forecasting Wind- 

 Generated Sea by Gerhard Neumann 



Based on recent observations of the composite nature of wind- 

 generated waves and on theoretical reasoning, the spectrum of ocean 

 waves is derived for a continuous sequence of wave components. The 

 properties of the wave spectrum are developed, and it is shown that 

 the spectrum has an optimum band where most of the spectral energy 

 is concentrated, and that the product of the frequency of the optimum 

 band and wind speed is constant. The range of periods with a sig- 

 nificant amount of energy, the width of the spectrum, determines the 

 actual wave pattern. It depends upon the wind speed and the state 

 of development of the waves at limited fetches and durations of wind 

 action. For practical purposes, a number E with dimensions (feet) 

 is introduced, which is proportional to the accumulated energy in 

 the wave spectrum. This value E is derived by integrating the wave 

 spectra, and permits easy determination of height characteristics 

 of the composite wave motion. Results are presented in the form of 

 co-cumulative power spectra for convenient use in practical wave 

 forecasting. 



T.M. No. 44 - June 1954 



Coast Erosion and the Development of Beach Profiles by Per Bruun 



The first part of this paper consists of a study of the Danish 

 North Sea coast including the following factors: coastline develop- 

 ment; development of beach profiles including comparison for 

 different wind and wave conditions; coast erosion and quantity of 

 littoral drift; and forecasting future development of shoreline and 

 beach profiles. Depth soundings since 1874 on the Lime Inlet Barriers 

 are used and treated statistically, explaining development of these 

 barriers and adjacent coasts. The second part consists of a study 

 of the Mission Bay, California area, including study of the develop- 

 ment of beach profiles with comparison for different wave conditions 

 seasonal fluctuations of profiles, and comparison of Danish and 

 Ca I i forn ia data. 



13 



