After the season of hurricanes and other tropical storms is 

 passed and all the possible desirable wave records have been obtained, the 

 field work will be completed. The remaining period of the contract will 

 be devoted to the analysis of the wave records and the interpretation of 

 the wave data. 



V. Waterways Experiment Station, Vicksburg, Mississippi, Progress 



Report on Model St^dy of the Effects of Tidal Inlets on Adjacent 

 Beaches . 



Progress during June 19^2 



1, Operation of the model for the first test was completed. Op- 

 erating conditions for this test are described in the following subparagraphs, 



a. Waves . The waves generated dxiring the test had a height of 0.1 

 ft. at mean tide level, a length of U.O ft., and a refsulting height/length 

 ratio of 0.025. The schedule of operation for positioning the wave machine 

 is given in the following tabulation. 



No. of Tidal Cycles Wave Direction From Direction of littoral Current^ 



Downbeach 



Downbeach 



None 



Downbeach 



Downbeach 



Downbeach 



»The littoral current is generated by pumping water from the basin 

 at one end of the beach and returning it at the opposite end. 



b. Littoral Currents . The characteristics of the littoral 

 currents generated are described above. 



c. Tides . The tides generated had a range of 0.1 ft. and a 

 period of 20 minutes. 



2. Stability of the unbroken beach required operation for 120 

 cycles, or two coiaplete cycles of wave positions as outlined in subpara- 

 graph 1 a above. An inlet 2.0 ft. wide, 8.0 ft. long, and 0.2 ft. deep 

 at mean tide level was then cut through the beach, and the cycle of wave 

 positions was resumed. The inlet closed off completely during tidal cycle 

 U2 after being opened, or imiaediately following the change in wave machine 

 position from 15° downbeach to l5° upbeach. The beach was surveyed at the 

 end of tidal cycles 60 and 120 before the inlet was cut through, and at 

 the end of cycle U2 after the inlet was cut through (cycle l62 from start 

 of test). The littoral drift was collected and measured at the downbeach 

 end at intervals of 5 tidal cycles. After being measured, the material was 

 returned to the basin at the upbeach end between the high water and low 

 water lines* 



29 



10 



15° 



Upbeach 



10 



30° Upbeach 



10 



15° 



Downbeach 



10 



15° 



Upbeach 



10 



30° 



Upbeach 



10 



0° 





