3.0
2.0
1.0
0.0
-1.0
0
100
200
300
400
500
600
700
800
Number of Observation - Jan 97
Figure 10. Tide gauge data, Apra Harbor, January 1997 (To convert feet to
meters, multiply by 0.3048)
complete data year, also illustrates that high tides are generally near msl while
low tides can deviate significantly from msl (Figure 11).
Because measurements are available at only one location, the model could
not be tested for accuracy at other locations in the study area. However, because
the inner regions of bays and harbors are relatively difficult to calibrate in com-
parison to deeper coastal and open ocean regions, it is expected that accurate
calculated water levels in the harbor assure accurate water-level calculations in
other regions of the model domain.
Calibration of the storm-surge model was conducted by driving the model
with six tidal constituents and comparing the results to gauge data. Table 6 gives
the tidal constituents at Apra Harbor as determined by NOS. The model was run
for a time period of eight days at the beginning of January 1997. The simulated
water level time series at the gauge location compares favorably to measure-
ments, which have been adjusted to msl during the simulated time period to
provide a consistent basis for comparison (Figure 12). This calibration was
considered sufficient for purposes of the present study.
Validation of Storm Surge Model
The storm surge model was validated by comparison of measured and calcu-
lated time-series water levels at Apra Harbor gauge for the period when Typhoon
33
Chapter 4
Implementation of Storm Surge Model
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