INTRODUCTION 
General Considerations 
Despite new and improved methods for measuring waves, currents, and 
other shore process elements, it remains relatively difficult to gain 
full understanding of the effects of wave and current systems on the 
size grading and sorting of beach and nearshore sands under natural field 
conditions. Simultaneous observation of water and sediment movement is 
complicated by the number of variables that must be measured, and by the 
local "noise" that tends to obscure underlying systematic effects. Asa 
result, an empirical model is commonly used, in which the patterns of 
areal variation in sediment properties are used to infer the nature of 
the process elements that are operative, and to evaluate their relative 
influence on the sediment properties. The empirical method generally in- 
cludes preparation of contour-type maps of the observed sedimentary 
attributes. These maps are useful for dynamical interpretations, but 
they may fail to bring out secondary effects; or, where these are dis- 
cernible, the maps may require highly subjective evaluation to distinguish 
between "meaningful" variations and local "noise."" Formal methods of map 
analysis (trend-surface analysis) have been applied successfully in 
various branches of geology, including the study of beach phenomena. In 
this paper the use of trend analysis is illustrated in a beach area in- 
volving a tidal inlet. 
Problem and Approach 
The problem under study is two-fold, involving (1) the distribution 
pattern of sediment size and sorting in the vicinity of the mouth of an 
inlet during an “instant" of maximum outflow, and (2) the pattern 
magnitude, and extent of inlet influence on the otherwise normal sediment 
distribution along the shore during this instant. Our approach to this 
problem is likewise two-fold, and involves (1) formulation of a model of 
the fluid-velocity distributions and resulting sediment responses associ- 
ated with the wave, longshore-current, and ebb tidal-current systems, and 
(2) analysis of the predicted trends in sedimentary responses, using 
appropriate natural data. 
THE MODEL 
A fluid process - sedimentary response model of an inlet entrance 
can be developed by first constructing the process-response model for an 
unmodified beach; i.e., one without an inlet. The general fluid motions 
over a gradually shoaling beach within the shoaling-wave, breaking-wave, 
and swash—backwash zones are described in various studies (cf. Eagleson, 
Glenne, and Dracup, 1963). Dynamic zones and directions of increase in 
