suitable for wave lengths shorter than eight times the depth. Rather 
severe restrictions inherent in the analogy between non-linear shallow 
water flow and two-dimensional perfect gas flow are also pointed out. 
A report, "Effect of Bottom Slope on Wave Diffraction" was given 
limited distribution by the University as Institute of Engineering 
Research Technical Report Series 89, Issue 8. The report discusses a 
laboratory study of the combined problem of wave diffraction and refrac- 
tion in a harbor. Several different bottom configurations were used in 
the protected area behind the breakwater, including both continuous slopes 
and abrupt changes. The resulting data are compared graphically with data 
for a horizontal slope in the sheltered area, such that refraction and 
shoaling would have no effect. 
Work was continued on study of the Mach-stem phenomenon, and a report 
"Diffraction of Periodic Waves Along a Vertical Breakwater for Small Angles 
of Incidence"' was given limited distribution by the University as Institute 
of Engineering Research Technical Report HEL-1-2. This report discusses 
the laboratory investigation of the reflection of periodic gravity waves 
as they advance along a straight vertical breakwater for the case of 
initial angle between the breakwater and the direction of incident wave 
advance of less than 20 degrees. The results were similar to phenomena 
observed for solitary waves, in that the waves were not regularly reflected 
from the breakwater, but a wave energy concentration was found next to the 
breakwater. Apparently this was a non-deep water phenomenon, 
Theoretical work was carried out on the problem of two-dimensional 
spectra of wind-generated waves, and preliminary tests were made in the 
newly modified 12-foot wide wind wave tank. 
V. Dr. W. C. Krumbein (Consultant). Study of Beach Phenomena. 
A report, “Geological Process -Response Model for Analysis of Beach 
Phenomena" has been prepared, and is published elsewhere in this Bulletin. 
This report describes beach processes and deposits in terms of a conceptual 
process-response model that considers the processes and deposits as sepa- 
rate though closely related aspects of shoreline phenomena. The model 
provides a formal framework for analysis of natural beaches as they may 
be modified or controlled by the coastal engineer. Further study is being 
made of the application of computing machine methods to the study of factors 
influencing beach characteristics and stability. 
A pilot study of sand sample data collected near the mouth of the Cape 
Fear River, North Carolina, has been subjected to analysis by computer 
methods and results are being analyzed. 
VI. Virginia Institute of Marine Science. Contract DA-49-055-civ-eng-63-6 
Study of Beach Response Relationships. 
A new contract was negotiated with the Virginia Institute of Marine 
Science to study beach and bottom processes and response elements in an 
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