hours along ranges 1 and 3, at 18 hours along range 5, and at 20 hours 

 along ranges 7 and 9. Near the end of the experiments the -0.8-foot con- 

 tour was nearly horizontal indicating possible equilibrium in the 6-foot 

 tank and was sloping downward in the 10-foot tank indicating continued 

 deposition at tliis depth. 



After the outer region had developed into a wide, flat shelf after 76 

 hours in the 6-foot tank and after 94 hours in the 10-foot tank, the depth 

 over the shelf varied laterally. In the 6-foot tank the depth increased 

 from 0.5 to 0.7 foot from range 1 to 5; in the 10-foot tank the depth 

 increased from 0.5 foot along range 1 to 0.9 foot along range 9. 



Near the end of each experiment the inner region was further eroded 

 forming a steeper slope just below the foreshore. In the 6-foot tank this 

 erosion (movement of the -0.5-foot contour) occurred after 135 hours and 

 with little lateral variation; in the 10-foot tank this erosion began at 

 160 hours along range 1 and 170 hours along range 3. Similar erosion may 

 have begun along the other three ranges during the last 5 hours of testing 

 as shown by the movement of the -0.2-foot contour along range 5, the -0.2- 

 and -0.3-foot contours along range 7, and the -0.2-, -0.3-, and -0.4-foot 

 contours along range 9 (see Figs. 13 to 17). 



(3) Offshore Zone . No significant difference was observed between 

 the 6- and 10-foot tanks in the way the offshore developed initially, and 

 only minor differences in the rate of deposition. The major difference 

 between the two tanks was the deposition after 100 hours. In the 6-foot 

 tank, material was deposited at depths of 1.0 foot and greater and the 

 shoreward boundary (-0.8-foot contour) of the offshore zone was stationary; 

 in the 10-foot tank, material was still being deposited at depths of 0.8 

 foot and greater as indicated by the seaward movement of the -0.8-foot 

 contour. 



The 6-foot tank had little lateral variation in the offshore zone, but 

 the 10-foot tank had significant lateral variation in rates of deposition 

 offshore and some lateral variation in the slope of this zone. Along range 

 1 the offshore was very steep and the -2.1-foot contour moved only 1.5 feet 

 in the 210 hours. Along range 9 the slope was not as great and the -2.1- 

 foot contour moved 4 feet (1.22 meters) in the 210 hours. 



2. Profile Reflectivity . 



The basic profile shapes which evolved during the profile development 

 are shown in Figure 9. Early profiles (broken line in Fig. 9) had a 

 steep foreshore, a short inshore with a longshore bar formed by the plung- 

 ing breaker, and a gently sloping offshore zone. Later profiles (dashline 

 in Fig. 9) also had a steep foreshore, but the inshore zone widened to a 

 long, flat shelf which terminated in a relatively steep offshore zone. 



Chesnutt and Galvin (1974) discussed the processes which reflect wave 

 energy from the movable bed in these experiments. The processes include 

 the conversion of potential energy stored in runup on the foreshore into 

 a seaward-traveling wave, the seaward radiation of energy from a plunging 



76 



