Percent Percent 
Sum of Squares Sum of Squares of 
Attributable to Deviations from 
Surface Surface Surface 
Linear Wile 88.8 
Quadratic 55 84.5 
Cubic 20.9 79.1 
Thus, the net contribution of the quadratic component is only 4.3 percent, 
and that of the cubic is only 5.4 percent. Nevertheless, we present the 
linear and cubic surfaces and their deviations to illustrate some aspects 
of the sorting pattern. 
Figures 17 and 18 show the linear surface and the deviations from it. 
The linear S, trend surface slopes to the east, or roughly perpendicular 
to the slope of the linear trend surface for mean grain size. The linear 
deviation map for sorting shows that the best sorting can be expected at 
the point where the inlet current intersects the breaker zone. This 
position coincides with the zone of greatest turbulence, as supported by 
field measurements (Harrison and Morales-Alamo, 1964) and theoretical 
models of beach dynamics (Miller and Zeigler, 1958), which suggest that 
it is in this zone that the best sorting and the largest grain sizes occur. 
Figures 19 and 20 show the cubic surface of the sorting coefficient 
and the deviations from the surface. The pattern on the cubic trend map 
is noticeably different from the cubic mean size map, in that the sorting 
surface rises from a low just north of the Rudee Inlet jetty, to high 
areas (i.e., poor sorting) seaward to the southeast of the inlet and to 
the northeast along the pier. 
Analysis of the cubic deviation map for Sg shows the best sorting 
to be centered at the intersection of the breaker zone with the combined 
flow of the inlet current and the longshore current. This is the zone of 
maximum turbulence, as noted previously. The zone of best sorting rapidly 
gives way to the zone of worst sorting (contour + 0.4) in a down-current 
(decreasing-velocity) direction. The actual center of the poorest sorting 
is seen to be just seaward of the central zone of inlet outflow. This is 
believed to reflect the rapid decrease of the longshore current component 
of the combined flow as it passes through the breaker zone. Hence, the 
coarser materials in transport along the shore appear to be deposited over 
a region of originally fine-grained sand. Thus the spread of the particle 
size distribution is greatest here, as shown by the large values represent— 
ing poorest sorting. 
