slope, which continued to erode as the foreshore retreated. The eroded 

 material was deposited mostly at depths of 0.7 and 0.8 foot up to 35 

 hours, which at 20 hours caused the breaker type to become mixed between 

 plunging and spilling. From 35 to 85 hours, the foreshore and inner 

 inshore continued to erode and the material was deposited in the offshore 

 zone at various depths . Between 60 and 65 hours the outer inshore eroded 

 at the 0.6-foot depth and thereafter the elevation remained below -0.6 

 foot. Between 75 and 95 hours significant erosion occurred at -0.7 foot 

 across the entire outer inshore. 



From 85 to 125 hours the foreshore and inner inshore continued to re- 

 treat as sand was eroded and deposited in large amounts in the outer 

 inshore and offshore zones. Deposition occurred first (85 to 95 hours) 

 in the higher elevations of the offshore zone, then in the outer edge of 

 the outer inshore (95 to 120 hours), and finally, throughout the offshore 

 zone after 120 hours. With the inshore zone much longer and flatter at 

 100 hours, the breaker at the seaward edge of the inshore zone became 

 consistently spilling and a secondary plunging-type breaker developed at 

 the shoreward edge of the inshore zone. 



At 125 hours the erosion of the foreshore and inner inshore ceased 

 and for the next 10 hours material was deposited in this region, with 

 some of this sand from erosion near station 8 (shoreward end of the 

 outer inshore) . After 135 hours the foreshore and inner inshore stabi- 

 lized, but the trough near station 8 continued to deepen as material 

 eroded from this region. Between 135 and 140 hours the shelf in the 

 outer inshore eroded to below -0.7 foot and thereafter the elevation re- 

 mained below -0.7 foot. Material continued to be deposited at depths of 

 -0.8 foot and lower. 



The daily mean water temperature with shoreline position is compared 

 in Figure 20. The figure shows no obvious correlation between erosion 

 rates and water temperature. The development of the trough near station 

 8 beginning at 110 hours coincided with the permanent temperature drop 

 below 10° Celsius at 110 hours, but that may have been coincidental. 



2. Profile Reflectivity . 



The basic profile shapes which evolved during the profile development 

 are shown in Figure 6. Early profiles (solid line in Fig. 6) had a steep 

 foreshore, a long flat shelf within the inshore, and a slightly steeper 

 offshore zone. Later profiles (broken line in Fig. 6) had a steep fore- 

 shore, a wider inshore with a large trough at the shoreward end, and a 

 relatively steep offshore zone. 



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

 energy from movable beds for four experiments with the same wave conditions 

 as used in this experiment. The processes include the conversion of poten- 

 tial energy stored in runup on the foreshore into a seaward-traveling wave, 

 the seaward radiation of energy from a plunging breaker, and the reflection 

 of the incident wave from the movable bed, particularly where the depth 

 over the movable bed changes significantly. Depth changes are significant 



46 



