beaches characteristically have a seaward-concave plan shape resulting 

 from erosion caused by refraction, diffraction, and reflection of waves 

 into the shadow zone behind the headland. Increasing radius of plan 

 curvature with distance from the headland suggested testing the logarith- 

 mic spiral, r = e^'^'^^o', as an approximation to the shape of headland-bay 

 beaches. Four natural beaches were selected for testing goodness of fit 

 to the log-spiral approximation: Spiral Beach, Sandy Hook, New Jersey; 

 Halfmoon Bay Beach, California; and Drakes Beach and Limantour Spit Beach 

 lying along the Drakes Bay shoreline to the north of San Francisco, Cali- 

 fornia. Results range from excellent to good with the best fit being the 

 Spiral Beach curvature for which the mean squared error in length of the 

 log-spiral radius vector is only 0.82 foot squared. 



216. ZENKOVITCH, V.P., "Formation of Accumulative Shore Forms in the Case 

 of Blocking of the Shore from Outside," Comptes Rendus (Doklady) 



de I'Academie des Sciences de I'URSS, U.S.S.R., Vol. LIV, No. 4, 

 1946, pp. 317-319. 



Keywords: Artificial headlands, Crenulate-shaped bay, Detached break- 

 water. Littoral transport. Ship hulls, Tombolo, Wave diffrac- 

 tion. Wave refraction 



A discussion of the processes involved in the growth of tombolos 

 behind natural or manmade offshore structures. 



217. ZWAMBORN, J. A., FROtlME, G.A.W., and FITZPATRICK, J.B., "Underwater 

 Mound for the Protection of Durban's Harbor," Prooeedings of the 

 12th Conference on Coastal Engineering, Vol. 2, 1970, pp. 975-994. 



Keywords: Hydraulic model (three-dimensional), Movable bed. Sand mound. 

 Sand tracer study. Sediment sizes. South Africa (Durban), 

 Submerged breakwater 



The construction of an underwater mound of sand for the protection 

 and improvement of Durban's beaches has been recommended on the basis of 

 intensive investigations. These investigations included prototype meas- 

 urements of beach changes as related to recorded sea conditions, basic 

 scaling tests in which these beach changes were reproduced to scale in 

 movable-bed models, and tests of the proposed underwater mound in models, 

 using different scales in order to eliminate possible scale effects. 



IV. SUBJECT HEADING INDEX 



15, 19, 20, 21, 22, 23, 



48, 51, 52, 53, 54, 58, 



80, 82, 85, 86, 87, 88, 



98, 100, 103, 104, 108, 109, 



110, 111, 112, 113, 121, 123, 127, 131, 132, 139, 140, 141, 142, 144, 



145, 147, 149, 152, 153, 155, 156, 157, 158, 159, 160, 161, 164, 167, 



170, 172, 174, 176, 182, 187, 190, 191, 192, 194, 198, 200, 202, 211 



Accretion: 















1, 3, 



4, 



6, 



8, 



10, 



13, 



14, 



24, 25, 



31, 



34, 



38, 



42, 



44, 



46, 



59, 65, 



66, 



67, 



72, 



73, 



76, 



77, 



89, 90, 



91, 



92, 



93, 



94, 



95, 



96, 



