fluid velocities are sketched diagrammatically in the left half of 
Figure 1. A model of the changes (responses) in grain size and sorting 
for this dynamic pattern was proposed by Miller and Zeigler (1958), and 
it is shown in the right half of Figure 1. The largest grain sizes and 
best sorting may be expected in the highest energy zone - that of the 
breaking waves - where the greatest turbulence exists. Because the fluid 
velocities diminish in directions away from the breaker zone, the mean 
particle size decreases and the sorting becomes poorer, as explained below. 
(Sorting worsens as more size classes are significantly represented in the 
size distribution.) The second step in construction of the inlet model 
studies here involves consideration of the velocity distribution of the 
"jet" issuing from the inlet channel into the ocean (Figure 2A) and its 
effect, in the presence of waves, upon the sediments at the entrance. 
French (1960) derives the velocity distribution at the exit for a two- 
dimensional channel issuing into relatively deep water. Bates and 
Freeman (1952) demonstrate that the theory of a two-dimensional jet issu- 
ing from a slot may be applied to sediment-laden inlet water entering the 
ocean, and that the theory explains the lunate shape of bars found off 
tidal inlets. For the velocity of outflow and channel dimensions of the 
inlet studied here, the angle of separation of the still-water boundaries 
approximates that shown in Figure 2B. 
A more realistic dynamic model requires assessment of the idealized 
jet flow (Figure 2B) both in the presence of waves and at a shoaled 
entrance. Figure 3A shows the general geometry of the nearshore bottom, 
based partly upon the scale model study of inlet development made by 
Saville, Caldwell, and Simmons (1957, Test 5) for an inlet system of 
similar dimensions to the natural inlet of this study, and partly upon 
the model postulated by Bruun and Gerritsen (1960, Figure 53). The zone 
of greatest turbulence in this model lies within the zone of breakers 
where they are intersected by outflow from the inlet (Figure 3B). The 
model predicts that the mean particle size (Mz) will decrease and the 
degree of sorting (Sj) will generally become poorer in directions of 
decreasing velocity gradient, as shown in Figure 3C. The progressive 
decrease in mean size is anticipated because of the well-established 
relation between bottom shear stress and transporting power (cf. Bruun 
and Lackey, 1962). A study of the sediments of the Beaufort Inlet area, 
North Carolina, by Batten (1962) shows this expected distribution of mean 
particle size. The fact that sorting will generally become poorer in 
directions of decreasing velocity gradient is dependent upon certain 
additional factors and assumptions. 
The sediment load in the outflowing current of the particular inlet 
under study has its origin in essentially one source, that caused by 
stirring up of material from the channel under turbulent flow conditions. 
This material consists of sand with a grain size distribution extending 
over five Wentworth sizes classes, as well as coarse silt and granules, 
usually as less than 8 percent of a given sample. 
