Keywords: Hydraulic model (three-dimensional). Wave diffraction. Wave 

 reflection 



By considering separately the two terms of the Sommerfield solution 

 of wave diffraction behind a semi-infinite breakwater, the influence of 

 the wave reflection from the structure can be evaluated. The diffraction 

 coefficient at any point can be obtained from a graph or table for full, 

 partial, or no reflection by the addition of two coefficients. Wave 

 heights were found to decrease consistently along the near-circular crests 

 for all distances from the breakwater tip. For a workable range of inci- 

 dent angle and distance from the breakwater, wave heights could be defined 

 by this arc distance from the shadow line expressed in wavelengths. These 

 relationships have been verified experimentally for all but the smallest 

 incident angle in proximity to the breakwater. 



Several theoretical solutions for the breakwater gap are shown to 

 be very similar, diverging only for small incident angles. New parameters 

 are provided which greatly simplify the presentation of information. The 

 scatter of past experimental data precludes the verification of this 

 theory and indicates the need for further tests, 



174. SIVARD, F.L., "Building a Beach With an Offshore Sill, Singer 

 Island, Florida," Shore and Beach, Vol. 39, No. 1, Apr. 1971, pp. 

 42-44. 



Keywords: Accretion, Compartmented breakwater. Construction procedures, 

 Florida (Singer Island), Littoral transport. Sandbags, Wave 

 attenuation 



The use of a sill constructed parallel to the shoreline to assist 

 in building and stabilizing a beach is not new; however, this type of 

 structure has not been as accepted as groins, bulkheads, and seawalls. 

 This paper discusses the dramatic success of one particular installation 

 constructed of sandfilled nylon bags. 



175. STIASSNIE, M., and DAGAN, G., "Wave Diffraction by Detached Break- 

 water," Journal of the Waterways, Harbors, and Coastal Engineering 

 Division, Vol. 98, No. WW2, May 1972, pp, 209-223, Discussion by 

 Y. Goda and T. Yoshimura, May 1973, pp, 285-288, 



Keywords: Detached breakwater. Permeable breakwater. Wave diffraction 



A thin barrier of finite length in water of finite depth and in- 

 finite extent is considered. An incident gravity wave, attacking an 

 obstacle from infinity, is diffracted and scattered by the thin barrier 

 (this represents a detached breakwater of large length to thickness ra- 

 tio) . The potential wave energy (i.e., the wave height) in the region 

 surrounding the obstacle was computed. Maps of the state of the sea 

 near the barrier were used to evaluate the breakwater performance, there- 

 fore, improving the design. Computations are carried out for a monochro- 

 matic incident wave and an impervious obstacle. The solution is extended 

 to the cases of a pervious barrier and a random incident wave. 



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