functioning or nonfunctioning was easily determined by visual inspection. 
101. Bypassing at groins. If only longshore sediment transport is 
considered, in principle, a high groin extending seaward well beyond the surf 
zone Will completely block the movement of sediment. In practice, the surf 
zone often extends beyond the end of a groin, allowing sediment to move past 
the structure. Rip currents and complex horizontal circulation patterns also 
act to transport sediment around a groin. During high tide and high wave con- 
ditions, suspended sediment moving alongshore may overtop a groin, i.e., the 
groin will function as a weir. If a groin contains voids, sediment tran- 
sported alongshore can pass through it. Recent groin inspection (Coastal 
Planning and Engineering, circa 1985) indicates that most functioning groins 
in the study area can be considered sediment tight. In the present report, 
longshore transport of sediment around the end of a groin is called bypassing, 
and transport of sediment over and through a groin is called transmission. 
There are no data sets available to directly estimate groin bypassing and 
transmission. 
102. Formally, GENESIS incorporates algorithms to represent sediment 
bypassing and transmission at groins. Transmission is represented by speci- 
fying a "permeability factor" ranging between O (no transmission) and 1 (com- 
plete transmission). Since the groins in the modeled area are mainly built of 
heavy, grouted stone, the permeability factor of functioning groins was set to 
0. It is recognized that a limited amount of overtopping will occur during 
high tide and high wave conditions, but specification of that effect is not 
possible at the present tiie. 
103. Bypassing of groins definitely occurs in the project area and must 
be represented in the model. In a theoretically complete analysis of the 
amount of sediment transported around a groin, both the cross-shore distribu- 
tion of the longshore sediment transport rate (Q in Equation 3) and the hori- 
zontal circulation and transport pattern must be known. Knowledge of the 
latter is beyond the present state of the art. For the former, there is not 
sufficient field data available to estimate the distribution of the transport 
rate. Although theoretical expressions exist to predict the cross-shore 
distribution of the longshore sediment transport rate, all pertain to ideal- 
ized conditions and none have been verified. In light of these circumstances, 
the simplest assumption that produces reasonable results is appropriate. 
104. In GENESIS, a “bypassing factor" is defined which ranges between 
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