"One Aspect of the Dynamics of a Coast OOOOGROOOl 



Partly Protected by a Row of Groynes" 

 Bakker, W. T. , Unpublished Manuscript. 

 (TC337 .B168) 



A mathematical theory is given about phenomena caused by groin 

 construction. Onshore and offshore transport are considered, but 

 not the influence of wave refraction and diffraction. Effects of 

 groins found in this study are: (1) in the middle of the protected 

 part of the coast the same processes occur as without groins, but 

 slower; (2) there are edge effects at the ends of a system where much 

 more accretion and erosion occur than without groins; and (3) the rate 

 of effect of the system depends upon the spacing of the groins. 



Key Words - Theory/Erosion/Accretion/System/Transport -normal/ 



"The Coastal Dynamics of Sand Waves and the 0000GR0002 



Influence of Breakwaters and Groynes" 

 Bakker, W. T. , Unpublished Manuscript, 

 pp. 1-7. (V.F. 3249-a BAK) 



At a coastline where littoral transport by waves prevails, pro- 

 gressive sand waves can exist, if there is a periodical varying dis- 

 turbance at one point on the coast and the coastline is at rest at 

 more than half a wavelength distance. These sand waves (or mega- 

 ripples) move from the point of disturbance to the part of the coast- 

 line that is at rest, independent of the direction of the littoral 

 transport. Wavelength increases with the period, but the velocity 

 of propagation decreases. A groin reflects a part of the sand wave. 

 The amplitude of the sand wave near the groin on the side of the 

 disturbance increases; a decrease occurs on the other side of the 

 groin. 



Key Words - Theory/lmpermeable/Erosion/Accretion/ 



"Influence of Protective Works on the Erosion 0000GR0003 



of the West Coast of Sylt, North Sea Coast of 



Germany" 



Fischer, 0., Translation, 12 pp. (TC273 .F9) 



Measurements of the beach on the west coast of Sylt showed that 

 groins and other existing protective structures were independent of 

 subsequent successions of accretion and erosion. The author proposes 

 that original studies maintained over a short period of time were 

 applied to a long period and did not constitute a proper basis for con- 

 clusions for beach protection. 



