NO. 122 - November 1960 



" Effects of Reefs and Bottom Slopes on Wind set-up in 

 Shallow Water " by E. G. Tickner 



Wind tides in shallow water were studied in a laboratory 

 channel with a reef, with various widths of openings, 

 located near the center of the channel and with various 

 slopes of the channel bottom other than horizontal. The 

 reef increased the set-up over a smooth bottom condition 

 by a factor of two for a solid reef and somewhat less 

 than this if the reef had an opening in it. The cross- 

 sectional integration procedure adequately describes the 

 surface profile for the sloping bottom, while the esti- 

 mated set-up assuming a constant depth equal to the 

 deepest part underestimates the actual set-up as much 

 as 2.75. 



NO. 123 - January 1961 



"Transient Wind Tides in Shallow Water " by E. G. Tickner 



Transient wind tides were studied in a laboratory channel 

 with various water depths and wind velocities. The 

 studies were divided into two parts, the first being 

 concerned with the surface time history and the second 

 the transient water motion. Results of the first part 

 indicate water surface "set-up" will overshoot its steady 

 state value by a factor of 2, being slightly higher for 

 deeper water depths and lower for shallower water depths. 

 Harder' s theory is adequate for predicting shallower 

 water set-up history, but not for deeper depths. Results 

 of the second part of the study indicate the surface 

 current reaches steady state very quickly and has a 

 value of 1/30 of the average wind velocity passing over 

 the surface for Reynold's number 2 x 10 3 or greater. 

 The water also oscillates and its oscillatory magnitude 

 can be predicted by using standard wave equations with 

 the wave height as the maximum set-up. A return flow 

 in the lower layers overcomes the slowly damped oscilla- 

 tory motion and a steady state flow is established. 



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