at different stations along the channel. The sign convention that erosion 

 rates are positive and deposition rates are negative is used hereafter. 



108. Testing procedure. At the start, the sediment model used the 

 bathymetric information from field surveys 1 and 2 for the channel. Outside 

 the channel, the bath3Tnetry used was identical to that used by the tide, wave, 

 and wave-induced current models for base condition since better detailed 

 Information was not available. 



109. To generate a wave sequence for 1 year for the verification and 

 base tests of the sediment model from the waves given in Table 3, the follow- 

 ing procedure was used. Each wave event in the sequence was assumed to be 

 steady with a duration of 4 hr. This is a reasonable assumption from field 

 experience and measurements, provided extreme storms are ruled out as done 

 here. Each wave condition (1 to 80) of Table 3 was identified with a fre- 

 quency of occurrence. During the running of the sediment model, wave condi- 

 tions were selected such that each of the 80 conditions occurred at the 

 frequency shown in Table 2. Thus, the waves used by the sediment model re- 

 flected nature in terms of wave statistics provided by WESWIS. The same waves 

 were used for base and Plan 1 tests. 



110. The sediment model used a time-step of 1 hr. This value was 

 considered optimum on the basis of testing and previous experience. The 

 computational sequence employed by the sediment model consisted of the fol- 

 lowing steps: 



a. Read in the local bathymetry. 



b. Pick the first wave condition. 



£. Read in the corresponding wave information (wave height, 



angle, period, wave-induced velocities, and setups/setdowns) . 



d. Read in the first hour of the tide data (tidal velocities and 

 elevations) . 



e. Combine the above quantities to obtain a total velocity field, 

 wave field, and local depth. 



f^. Compute sediment transport quantities and the associated ero- 

 sion and deposition rates. 



g. Repeat steps d, e, and £ at 1-hr intervals for a total of 

 4 hr. 



h. Pick the next wave condition and continue steps c through £, 

 etc. 



As indicated previously, the local still-water depth h for each cell was 



updated at each time-step based on the erosion or deposition in the cell. The 



62 



