(2) 1.90-Second Wave . The most dramatic evidence for a tempera- 

 ture effect was in experiment 70X-06. At 22 hours the water temperature 

 dropped from 28° to 18° Celsius and the shoreline recession rate increas- 

 ed from 0.06 to 0.14 foot per hour (Fig. 62, a). (After sand feeding was 

 begun the experiments had little value to this analysis.) In experiment 

 70X-10 (Fig. 62, b) temperature data collection did not begin until 38 

 hours and the comparison of shoreline recession and temperature between 

 38 and 62 hours is not very conclusive. The temperature was fairly high 

 (25° to 30° Celsius) and the shoreline recession rate was 0.08 foot per 

 hour. 



In experiments 71Y-06 and 71Y-10 (Fig. 63) the shoreline recession 

 rates were high during the first few hours (0.113 foot per hour in ex- 

 periment 71Y-06 and 0.133 foot per hour in experiment 71Y-10). However, 

 the shoreline recession rate soon decreased to 0.025 foot per hour in 

 experiment 71Y-06 and 0.016 foot per hour in experiment 71Y-10, although 

 the temperature remained at a high value. The recession rate remained 

 constant throughout the remainder of the experiments, even though the 

 temperature dropped sharply several times, which tends to disprove the 

 effect suggested by experiment 70X-06. However, the mutual agreement 

 between experiments 70X-06 and 71Y-06 is important. Between 10 and 50 

 hours the recession rate was quite high in experiment 70X-06 while the 

 temperature dropped and the recession rate was much lower in experiment 

 71Y-06 while the temperature remained high. 



In experiment 72D-06 the shoreline retreated at a rate of 0.05 foot 

 per hour, which means that the volume rate of erosion was continually 

 increasing, while the temperature decreased from 20° to 6° Celsius (Fig. 

 64) . The erosion of the trough in the inshore zone after the shoreline 

 recession stopped occurred when the temperature was at its lowest values. 



(3) 2.35-Second Wave . In experiment 72B-06 (Fig. 65, a) the 

 shoreline was stable and the profile was at equilibrium, even though the 

 temperature took two 8° drops. In experiment 72B-10 (Fig. 65, b) the 

 shoreline retreated at a very slow rate, which varied between 0.004 and 

 0.018 foot (0.12 and 0.55 centimeter) per hour, while the temperature 

 varied between 30° and 20° Celsius, with drops of 5° and 9°. Compared 

 to the 1.90-second experiments (Figs. 62, 63, and 64), the temperature 

 remained fairly high and the recession rate was small. 



(4) 3.75-Second Wave . In experiment 72A-06 (Fig. 66, a) the 

 shoreline recession rate was constant, meaning that the volume erosion 

 rate was increasing, while the water temperature increased. In experi- 

 ment 72A-10 (Fig. 66, b) the shoreline was stable as the profile was at 

 or near equilibrium and the temperature rose initially and then remained 

 fairly constant. 



(5) Discussion . Experiment 70X-06 supports the hypothesis that 

 decreasing water temperature causes increasing erosion. Although the 

 shoreline recession rate did not respond to sharp drops in temperature 



in experiments 71Y-06, 71Y-10, 72D-06, 72B-06, and 72B-10, the comparison 

 of those experiments with 70X-06 supports the general hypothesis that the 



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