verification procedure could not be followed because of the enormous amount of 
unrecorded shore protection activity that has taken place and the recorded 
erratic movement of the shoreline position (cf., Appendix D). If the time 
history of all construction and beach fill activity were known, GENESIS could, 
in principle, incorporate it. As an acceptable alternative, calibration and 
verification were made for the critical zone of Sandy Hook, which is conti- 
guous with the north end of the project. This section of beach has exper- 
ienced minimal human intervention, except for occasional placement of beach- 
fill. Dates of major beachfills are believed to be known and could be 
avoided. Major beachfills were documented in the early 1960's, November 1982 
through August 1984, and in 1984 (Slezak et al. 1984). Thus, these intervals 
were not included in the calibration and verification. Phillips (1985) tenta- 
tively concluded that shoreline change at the critical zone could not be 
explained by any known process information. However, as described below, 
shoreline change at the critical zone occurring in recent times was readily 
amenable to quantification by GENESIS. 
108. In addition to the direct calibration and verification procedure, 
two indirect tests of model prediction were made. One was a qualitative check 
to ascertain that calculated and observed angles and sizes of groin fillets 
were in general agreement. Typical values of updrift fillet angle obtained 
from the model were 10-16 deg, whereas measured angles were in the range of 
14-16 deg. This is a qualitative verification of the sediment bypass algo- 
rithm. The other test (described in paragraphs 121-124) was calculation of 
the net longshore sediment transport rate at specified locations along the 
coast. 
109. In the calibration and verification procedure, visual comparisons 
were made by plotting calculated and measured shorelines. In addition, a dif- 
ference indicator Ydiff was devised to provide a more objective fitting cri- 
terion. The difference indicator is defined as the sum of the absolute dif- 
ferences between measured and calculated shoreline positions at each grid 
point: 
N 
Ydiff = )/ |Ymeas - Yeale| , (5) 
=H 
where the summation runs over all grid cells, and 
Ymeas = measured shoreline position 
Yeale = calculated shoreline position 
57 
