traditionally judged to "feel" the bottom. Therefore, an investigation into 
the effect of the borrow sites on the wave refraction pattern was made. 
Emphasis was given to calculations for the northern site as it contains more 
suitable and more plentiful quantities of usable fill material, and is the 
probable major source. 
67. Previous studies. The phenomenon of wave refraction over dredged 
holes has received little attention. Only two technical papers could be found 
(Motyka and Willis 1975; Horikawa, Sasaki, and Sakuramoto 1977) that treat the 
subject. In addition to investigating wave refraction over dredged holes, 
both studies employed a simple version of the shoreline model described in 
Part IV to calculate shoreline change. These studies were of a preliminary 
nature but do provide some practical guidance. As expected, the refraction 
pattern was found to notably change with increase in dredged depth at a given 
water depth and with increase in wave period. Motyka and Willis (1975) state 
that, at the time of their study, beach mining in the United Kingdom was 
restricted to depths greater than 18 m (60 ft). 
68. Calculation conditions. Two subgrids derived from the main depth 
grid were used in calculation of refraction over the borrow sites. The sub- 
grid for the northern site ran from Long Branch to Sandy Hook Lighthouse, and 
the subgrid for the southern area ran from Manasquan Inlet to Deal Lake. 
Table 4 (northern site) and Table 5 (southern site) list the calculated com- 
binations of deepwater wave conditions and dredged depths. 
69. As described in Appendix E, the northern site cannot be dredged 
uniformly because the usable sediment source lies in irregularly-shaped lenses 
of varying thicknesses. For greater dredged depths, the borrow hole was "dug" 
on the grid at allowable depths in the appropriate regions. Three borrow hole 
configurations were simulated for the northern site and two for the southern 
site. 
Calculation results 
70. The 20 refraction run conditions for the northern site are listed 
in Table 4, and the 15 conditions for the southern site are listed in Table 5. 
A wave direction of 7.5 deg corresponds to a wave out of the east, the quad- 
rant associated with much higher than average wave heights in the hindcast 
(Table 2). For this direction, waves of three periods (4, 8, and 12 sec) were 
run to investigate the effect of wave period. The effect of incident wave 
direction was investigated by specifying waves out of the east-northeast 
42 
