systematic effects present along the whole stretch of beach. The local 
quadratic map in Figure 11, on the other hand, contains the regional 
effect as well as the influence of the inlet. As a result, we may sub- 
tract one map from the other to obtain a map of the area of influence of 
the inlet itself. This (Figure 15) shows that the inlet affects an area 
that extends as a bulge seaward from the inlet mouth, diminishing to zero 
in the vicinity of the pier as well as oceanward to the southeast. This 
bulge is somewhat asymmetrical, reflecting its distortion and displacement 
by the northward-flowing shore current. The maximum departure of particle 
size equals 0.12 mm. 
The implications of Figure 15 are that Rudee Inlet exerts an appreciable 
effect on the nearshore bottom sediment in a very limited area, in contrast 
to the length of the beach segment between Transects 1 and 3 in Figure 5. 
That is, the distance between the limiting zero contours in Figure 11 is of 
the order of 0.1 mile (0.16 km.), as against a length of more than 1.5 miles 
(2.4 km.) between the end transects. This, in turn, is a short segment of 
the essentially straight coastline extending south of Cape Henry for a 
number of miles. It may be anticipated from these relative scales that 
the influence of an inlet similar to the one studied here could very easily 
be missed in subsurface exploration of ancient sediments for oil or gas, 
say, or even in the study of present day beach patterns involving a closed 
inlet, where its effect would be that of a small deviation on a large-scale 
trend surface map. 
ANALYSIS OF SAND SORTING DATA 
The preceding discussion is based wholly on the patterns of areal 
variation in mean grain size. It is appropriate to ask whether the areal 
pattern of sediment sorting sheds any additional light on the area of 
influence of the inlet, or on the dynamic processes that take place in its 
vicinity. 
Figure 16 shows the observed map of the sorting coefficient, So, in 
the study area. Its pattern is distinctly different from that of mean 
particle size in Figure 8, although there is a tendency for low values 
(that is, good sorting) to lie approximately in the area of largest mean 
grain size. For example, the contour line 0.5 on the sorting map lies 
peripherally to the contour of maximum mean grain size (0.50 mm.). A 
dominant area of high values (poor sorting) lies beyond the breaker zone on 
the seaward side of the inlet current. In general,sorting becomes poorer 
to the east, whereas the mean particle size tends to increase northward. 
Trend Surfaces of the Sorting Coefficient. The linear, quadratic, 
and cubic surfaces were fitted to the observed S, data of Figure 16. The 
surfaces are very weak in comparison even with the mean size surfaces, as 
shown by the following sum of squares summary for S,: 
