Run 4

fully developed experiment for detailed data collection. Other initial conditions

determined from the previous preliminary experiments were used. Initial mini-

mum cross-sectional area was 0.04 sq m (0.45 sq ft). After 15 tidal cycles of

tides-only condition, the minimum area had stabilized at 0.05 sq m (0.57 sq ft).

The inlet width remained close to the initial width of 0.6 m (2.0 ft), with only

slight slumping of its steep sides. Depths had increased from 0.07 to 0.09 m (0.22

to 0.29 ft). The sediment removed from the channel had transported both seaward

and bayward initiating the creation of ebb and flood shoals, respectively. Starting

with cycle 16, the 1-sec, 3-cm wave was initiated, with the generator parallel to

the beach. The response was a slight widening at the oceanward side of the inlet

(Figure 6, hour 31) and a bayward migration of the inlet itself as sediment was

removed gradually from the inlet shoulders and introduced into the ebb and flood

shoals. Figure 7 shows the inlet at the conclusion of the test at tidal cycle 144.

The minimum area had migrated bayward and channel length shortened.

The bay tide range was nearly constant for the entire experiment, with a span

between 0.3 and 0.33 cm (0.12 and 0.13 in.), which was one-tenth the ocean

range. Figure 8 shows the ocean and bay tides. Velocity measurements were col-

lected at one location within the inlet. Because the sensor was on a three-legged

stand in the channel, it was not moved during the study. As the cross section in

the channel changed, minimum area migrated. Also, a shoal developed, then

moved. Therefore, a variation in velocity accompanied channel morphological

variations. However, as the experiment was concluding, the velocity measure-

ment, though not in the center of the minimum cross section, was located such

that measurements representative of those in the minimum cross section were ob-

tained. Maximum currents were 0.31 m/sec (1.03 ft/sec) at cycle 144 at a mini-

mum area of 0.0606 sq m (0.652 sq ft).

Run 5

This experiment was conducted with the 105-min tide period. Based on re-

sults of the previous experiment, the inlet length was decreased to reduce run

time. The inlet area increased from an initial minimum cross-sectional area of

0.053 sq m (0.57 sq ft) to an equilibrium area of 0.12 sq m (1.30 sq ft) by tidal

cycle 16 with a maximum current of 0.29 m/sec (0.94 ft/sec). Figure 9 shows the

widening of the inlet from the tide-only condition. The wave generator was then

run with the standard wave condition until a new equilibrium was reached after

an additional 13 tidal cycles. The minimum area increased to 0.148 sq m

(1.59 sq ft), with the maximum current dropping to 0.27 m/sec (0.89 ft/sec). Fig-

ure 9 shows the widening of the channel caused by the tidal currents. It is inter-

esting to note from Table 2 that the tidal prism is significantly larger for Run 5

due to the longer tidal period, allowing greater filling of the bay and different

Chapter 4 Experiments and Results