A field experiment designed to test the hypothesis
that infragravity and lower frequency waves influence the
patterns of erosion and deposition on the beach foreshore
has been carried out. The data show coherent fluctuations
in the foreshore sediment level which can be related to low
frequency wave motions. The fluctuations have heights of
up to 6 cm with typical time scales of 8 to 10 minutes.
They can be characterized in two ways: by the progression
of the fluctuations up the foreshore slope (landward), and
by the decrease in the RNS height of the fluctuations as
they progress landward. The velocity of migration also
changes as the fluctuations progress landward. Analysis of
runup time series obtained by time-lapse photography concurrent
with the sediment level measurements reveals long-period
waves of undetermined origin at frequencies and
phases which strongly suggest that the waves force the
original perturbation in sediment level.
In order to better understand the characteristics of
these sediment level fluctuations, a numerical model of
sediment transport on the foreshore has been developed.
Gradients in sediment transport define erosional and depositional
areas on the foreshore. Runup velocities were
modeled and the results were used in the sediment transport
model. The model predicts that any perturbation in foreshore
elevation will progress landward while decreasing in
amplitude and in velocity, thereby matching the field
observations. Relationships between beach slope and the
profile response clarified by this model are used to explain
the initial formation of the perturbations of sediment
level. / Graduation date: 1984
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/27799 |
| Date | 10 February 1984 |
| Creators | Howd, Peter A. |
| Contributors | Holman, Robert A. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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