EM 1110-2-1100 (Part III)
30 Apr 02
Figure III-2-48.
Wave transformation hindcast to RCPWAVE grid (Gravens 1990a)
(f) Potential longshore sand transport rates were calculated using the transformed wave estimates and
relationships similar to Equation 2-7 for the various shoreline orientations within the project reach. These
potential transport rates are presented in the form of a total littoral drift rose (Walton 1972, Walton and Dean
1973) (Figure III-2-49). The curve with the circular symbols in Figure III-2-49 represents the average
downcoast littoral drift for the 20-year Northern Hemisphere hindcast of sea and swell wave conditions. The
curves with "x" symbols and "" symbols in Figure III-2-49 represent the average upcoast littoral drift for
the available 2 years of Southern Hemisphere swell wave estimates. It is interesting to note that there is a
reversal in the direction of the average net longshore littoral drift and that this reversal occurs at different
shoreline orientations depending on the time series of southern swell wave conditions used in the calculation.
(g) The results of the final model calibration simulation, 1963 to 1970, are presented in Figure III-2-50.
In model calibration, the calibration parameters K1 and K2 ranged between 0.8 and 0.2; values of these
parameters that best estimated gross and net longshore sand transport rates and reproduced observed shoreline
change were determined to be K1 = 0.45 and K2 = 0.4. Calibration results lead to three general observations.
First, in the Anaheim Bay entrance area (between alongshore coordinates 220 and 260), there are significant
differences between the calculated and measured shoreline positions. These differences are due in part to the
reflection of waves from the east Anaheim Bay jetty (a process which was not modeled) and to a massive
(4 million-cu-yd) renourishment of the Surfside-Sunset feeder beach in 1964. The percentage of fine material
contained in the beach fill is unknown; consequently, the initial losses of fill material could not be estimated
or accounted for in the model. Model results in this region should be viewed with caution.
III-2-84
Longshore Sediment Transport
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