torabolo formation limits, as well as accumulation percentages in total 

 or partial torabolo formation. Most of the parameters prevailing in tom- 

 bolo formation were varied--the length of the obstacle, the gap between 

 the beach and the obstacle, the angle formed between the long axis of 

 the structure and the incident wave, the wave height and its period. 



Several observations on the nature of shoreline movement near 

 three old sunken ships on the coast of Salina Cruz, Oaxaca, Mexico, were 

 compared with the experimental results; these showed great similarity. 

 Comparative tests with groins and tombolos were made in the same model 

 to define the order of effectiveness. 



205. VICHETPAN, N., "Equilibrium Shapes of Coastline in Plan," Masters 

 Thesis, A^ian Institute of Technology, Bangkok, Thailand, 1969. 



Keywords: Crenulate-shaped bay. Hydraulic model (three-dimensional). 

 Littoral transport. Movable bed. Wave diffraction. Wave 

 refraction 



If a straight sedimentary coastline with headlands suffers persis- 

 tent waves from an oblique direction and no replenishment is provided for 

 material removed downcoast, it will assume a crenulate shape which becomes 

 progressively more indented. Finally, a shape is reached which is in 

 equilibrium with the waves. The development of such equilibrium-shaped 

 bays was studied by means of a model in which wave direction and wave 

 periods were the sole variables. Thus, the wave height, water depth, 

 beach height, and sedimentary material were the same throughout. 



The shape of the bay at various stages from straight line to fully 

 stable was measured after various wave durations, It was found that the 

 major curved part of the waterline was a logarithmic spiral, the constant 

 of which varied throughout. A consistent pattern was observed for this 

 constant for the three wave approach angles of 30°, 45°, and 60°, and the 

 three wave periods of 0.6, 1.0, and 1.4 seconds. 



206. VISENTINI, M. , PANCINI, G., and TEUSCHL, E., Untitled report to 

 SII-CI (Protection Works Adopted to Limit Erosion Along the Open 

 Coast, How They Work, Reference to Model Experiments), XVIIth 

 International Navigation Congress ^ Lisbon, Portugal, 1949, pp. 105- 

 134 (in French) . 



Keywords: Detached breakwater, Italy (Corroglio) , Segmented breakwater, 

 Tombolo 



This report discusses general considerations in the selection and 

 the construction of protective works on an open shore to prevent erosion 

 of alluvial beaches. The conditions that exist on the Venetian coastline 

 are discussed, taking into account the various protective works used to 

 protect the lagoons that lie behind the beaches, The causes of beach 

 erosion in Venetia are briefly recounted, as well as the localities where 

 such erosion is most marked. Other Italian beaches are also reviewed. 



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