52 



in the navigation openings. Undesirable current velocities in ungated 

 navigation openings might also be prevented by use of auxiliary sluice 

 gates as mentioned above. 



77- It will be noted that current velocities measured in the navi- 

 gation openings in the model are appreciably less than those measured in 

 the flume containing the undistorted models of the navigation openings 

 for comparable conditions of head differential. The major difference be- 

 tween velocities for the two conditions is attributable to location of 

 the points of measurement; the verticals observed in the model were 

 located on the center of the sills^ while the cross sections observed in 

 the flume were located in the most contracted portion of the jet. Meas- 

 urements made at identical points in the model and flimie for comparable 

 head differentials indicate that use of steady state flows in the flume 

 resulted in velocities about five per cent higher than occurred in the 

 model under tidal flow conditions, for the reason that velocities ap- 

 parently do not quite attain steady state values under tidal conditions. 

 Velocity data presented on figs. 19 through 22 are therefore considered 

 to be of the order of five per cent higher than can be expected in nature 

 under tidal conditions . 



