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P. Wang et al. / Coastal Engineering 46 (2002) 175211
Fig. 11. Spectra of the temporal variations of suspended sediment concentration at the breaker line for spilling (upper panel) and plunging (lower
panel) cases.
1 cm above bed (not shown in Fig. 10) and not above
Overall, the shapes of the power spectral density of
this level. Across the mid-surf zone for both spilling
sediment-concentration variations are significantly
and plunging cases, temporal variation of sediment
different from those of water-level fluctuation and
concentration at the incident-wave frequencies can
cross-shore current. Generally, the spectral density
only be identified at 1 cm from bed. These indicate
did not exhibit a strong peak at the principal inci-
that signatures at the incident-wave frequencies are
dent-wave frequency, i.e., 1.5 s (0.67 Hz) for the
only evident in the region near the bed. The low-
spilling case and 3.0 s (0.33 Hz) for the plunging
frequency peaks at 50 s (0.02 Hz) to 100 s (0.01 Hz)
case. The spectra revealed slight peaks for the con-
in the concentration spectra are also artifacts of the
centration measured 3 and 7 cm above the bed at the
present spectral analysis method, similar to those in
plunging breaker line. At the spilling breaker line, a
longshore-current spectra (Fig. 8).
noticeable wave-frequency peak was only observed at
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