BEACH EROSION LITERATURE 



There are listed below some recent acquisitions of the Board's lib- 

 rary which are considered to be of general interest,, Copies of these 

 publications can be obtained on 30-day loan by interested official agen- 

 cies o 



"Sea Waves and Microseisms," J„ Darbyshire, Admiralty Research Laboratory,, 

 Teddington, England, A°R„L„/Ro l/l03o50/W, March 1948, 



The paper reports the comparison of wave records at Perranporth with 

 with simultaneous seismorgraph records at Kew made to detect the 

 influence of two mid-Atlantic storms on microseismic activity,. 

 Meteorological charts for the storms are shown,, Graphs show the 

 spectra of the waves and microseisms obtained by submitting the 

 records to frequency analysis „ One of the conclusions states that 

 the period of the waves is' double that of the corresponding micro- 

 seisms o 



"A Theory of Microseism Genera ti on , " M» So Longnet-Higgins-, Admiralty 

 Research Laboratory, Teddington, England, A°R°Lo/Ro2/L03°50/w" s 

 August 194.8o 



In the report a theoretical justification is given for the theory 

 that microseisms of period 3 to 10 seconds originate in regions of 

 wave interference in the sea„ It is shown that the unattenuated 

 pressure variations in a standing wave are due to simultaneous 

 changes in the vertical momentum of the 'wfople wave train „ Varia- 

 tions in the mean pressure occur only when there is interference 

 between groups of waves of the same frequency travelling in op- 

 posite directions, they are twice the wave frequency and are propor- 

 tional to the product of the amplitudes of the two opposing groups „ 

 Simultaneous pressure variations over a wide area will give rise 

 to compression in the water and sea bed,, By considering the effect 

 of an application of pressure to the surface of the water it is 

 shown that the displacement of the ground should be of the same 

 order of magnitude as that observed D The conditions of wave inter- 

 ference necessary for microseism generation should occur in a moving 

 cyclonic depression or to a less extent when waves are reflected 

 from a steep coast The doubling of the wave frequency implied by 

 theory is well supported by observation 



"Water Tables in Marine Beaches," K„ 0„ Emery and J F« Foster , Journal 

 of Marine Research, Vol,, VIII, No„ 3 S November 1948 . 



An attempt to learn the relationships between beach characteristics 

 and changing water levels within the beach is made in this study,, 

 Measurements of the changing water table profiles in several 

 beaches throughout a tidal cycle show the presence of an inter- 

 change of water between the ocean and the sand pores „ Water escapes 

 from the beach during ebb tide with a velocity sufficient to 



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