SUMMARY REMARKS 
A model (Figure 4B) of sedimentation at the mouth of a small, con- 
trolled tidal inlet has been developed from anticipated fluid-—velocity 
distributions. It deals with the distributions of mean size (Mz) and 
degree of sorting (Sj), in response to forces induced by the ebb flow 
from the inlet channel and by wave fronts that approach the shoreline 
obliquely. 
The model predicts that the largest particle sizes and the best 
sorting will occur in the region where the longshore and inlet currents 
intersect, that sorting will be poorest just seaward of this intersection 
(also seaward of the breaker zone), and that mean size will decrease and 
sorting improve in directions of decreasing velocity gradient beyond the 
breaker zone. Observed patterns of Mz and Sy agree with these predictions. 
The model also predicts that particles of relatively small diameter 
(originating in the inlet and longshore currents) will be deposited upon 
a surface of normally sized and sorted beach sands on either side of the 
outflowing current. The prediction is confirmed by analysis of weak 
trends for Mz and Sg shown on residual maps for cubic trend surfaces, for 
the regions flanking the inlet outflow. (The trends can be understood by 
assuming that the Mz and S, patterns of the depositional surface have 
been inherited from normal fluid-velocity distributions common to the 
shoaling wave zone of the previous high tide.) 
It is demonstrated that it is possible to delimit the boundary, 
estimate the magnitude, and describe the pattern of inlet influence for 
a given sediment property (such as Mz and So) upon an otherwise unmodified 
beach by subtracting the trend surface for the area of the inlet entrance 
from the corresponding trend surface for the unmodified beach. 
The present study illustrates that trend surface analysis furnishes 
a method for "taking apart'' raw observations in order to distinguish 
between large-scale (systematic) effects and small-scale (presumably non- 
systematic) effects in map data. It is noteworthy in this study that the 
deviation maps are on the whole more informative than the trend surface 
maps, although the low-order surfaces, despite their relative weakness on 
a sum of squares basis, do present geologically reasonable patterns in 
relation to outflow from Rudee Inlet. The large content of the original 
map variability contained in the deviation maps, especially for the 
sorting coefficient, implies that a substantial amount of geological in- 
formation is contained in the deviations, which definitely cannot be 
discarded simply as random noise. 
In the long run an essential element in beach studies will be the 
dynamic model postulated for the situation. If the particular model can 
be expressed quantitatively (as it can in some instances), field 
