After 100 hours the position of the outer edge of the inshore zone 

 became stable and the material was deposited farther offshore in depths 

 greater than 0.9 foot. After 135 hours the inner region of the inshore 

 zone was again eroded, creating a steeper slope in this region, while the 

 temperature dropped below 10° Celsius. The material was deposited at the 

 outer edge of the inshore zone in depths of 0.6 and 0.7 foot. 



The definite decrease in median grain size in the seaward direction 

 indicates that the finer material was eroded from the nearshore and depos- 

 ited offshore, as expected. 



b. Experiment 70X-1Q . Important changes in the profile shape, breaker 

 condition, and water temperature are summarized in Table 13. The daily 

 mean water temperature and the shoreline position are compared in Figure 37. 



During the first 10 hours the foreshore retreated at an average rate 

 of 0.05 foot per hour. As the foreshore retreated, a bar was formed in 

 the inner inshore region by the plunging breaker and the eroded material 

 was deposited at depths greater than 0.9 foot. 



From 12 to 62 hours the foreshore retreated at a faster rate [approxi- 

 mately 0.08 foot per hour). This further widened the inner region as the 

 position of the -0.5-foot contour remained stationary during the first 50 

 hours. As the material was deposited offshore, the seaward edge of the 

 inshore zone (-0.8-foot depth) moved seaward, creating a flatter outer 

 region of the inshore zone and a steeper offshore slope. 



After 40 hours the breaker began to move seaward (with the -0.6-foot 

 contour) , and between 62 and 70 hours the breaker type changed from plung- 

 ing to spilling as the slope in the inshore zone became flatter. After 

 84 hours the waves broke at a depth of 0.7 foot. From 40 to 94 hours the 

 bar in the inner inshore disappeared as the breaker moved seaward and 

 changed from plunging to spilling. 



No apparent lateral variation occurred in the development of the outer 

 edge of the inshore zone; i.e., the movement of the -0.8-foot contour 

 intercept. However, the changes within the inshore zone did vary laterally. 

 Along each profile, as the bar in the inner region disappeared, the shelf 

 in the outer region developed (see Fig. 21). The time when this change 

 occurred varied laterally across the tank, starting first along range 1 

 and later along range 9. 



The inner inshore remained stable from 94 to 160 hours while the beach- 

 fill material was eroded at the average or an above average rate and was 

 deposited in the offshore zone. After 125 hours, more material was depos- 

 ited on the left side (ranges 5, 7, and 9) than on the right (ranges 1 and 

 3). 



After 160 hours, however, the beach-fill material was eroded at an 

 average or below average rate while the inner inshore along ranges 1 and 3 

 experienced further erosion. If the experiment had continued past 210 



73 



