profile change was smaller than that pertaining to the wave tank calibrations 

 involving monochromatic waves (field value: K = 0.7 10" 6 m 4 /N with a range of 

 0.4 10" 6 to 0.9 10" 6 m 4 /N). Values of e and D eq used in the field tests 

 were held the same as determined for the laboratory conditions; e = 0.001 

 m 2 /sec, and values of D eq specified to be 25% lower than those given by 

 Moore (1982). 



RESULTS 



Example of Model Test 



Figure 3a shows a comparison of measured and calculated profiles for CE 

 Case 400, for which: initial slope = 1/15; grain size =0.22 mm; wave height 

 and period of 1.62 m and 5.6 sec in the horizontal section of the tank (depth 

 = 4.42 m) ; and constant water level. These steep waves (H /L = 0.035) cut 

 back the foreshore to produce a vertical scarp, and a bar formed near the 

 break point which grew and moved offshore with continued wave action. The 

 numerical model satisfactorily reproduced the observed erosion and main bar 

 development. Simulated bar growth was initially rapid and gradually slowed as 

 the bar moved offshore to reach a location close to that of the observed bar 

 at the end of the run (40 hr) . 



Figure 3b shows the calculated result of a hypothetical situation in which 

 a seawall was placed at the initial still -water shoreline of Case 400. The 

 final calculated profile for the original situation (Fig 3a) is shown as the 

 heavier line. Development of the main breakpoint bar was quite similar for 

 the seawall -backed beach and natural beach, whereas the profile showed greater 

 erosion near the wall, representing local scour. In this example wave reflec- 

 tion at the wall was not taken into account. 

 Adjustment of Beach Fill to Wave Action 



The numerical model was applied to investigate the performance of repre- 

 sentative beach fill cross-sections. For this purpose, a design hydrograph 

 consisting of varying waves and water level was fabricated for use in the 

 simulations. A schematic of the time history of wave conditions and water 

 level for the 30 -day test period is given in Figure 4. 



The first 21 days consist of constant waves and water level, with a wave 

 height of 0.5 m and wave period of 8 sec. These values are meant to represent 



98 



