5
Development of
Overtopping and Stage-
Frequency Relationships
Overtopping-frequency relationships were developed for the project area
along the north side of Cabras Island, Guam, in four tasks. First, the training set
of storms was developed from a storm database for the western Pacific Ocean,
and the PBL model was applied to calculate wind fields associated with each
storm in the training set. Second, the storm-surge model was applied with wind
and atmospheric pressure forcing from the PBL model as time-dependent input.
Time-series of storm-surge elevations associated with each storm were calcu-
lated for specified stations. Third, time series of wave parameters were calcu-
lated by application of the wave and wave-transformation models. Time series of
ponding level, setup, runup, and overtopping were calculated for each profile
location in the study site. Fourth, the EST was applied to compute overtopping-
frequency relationships based on the typhoon event parameters and calculated
overtopping rates.
The harbor side analysis included two additional tasks. First, wind, offshore
wave, and storm surge information from ocean modeling tasks was used to
develop storm water level elevations at the commercial dock along the south side
of Cabras Island. Second, the EST was applied to compute stage-frequency
relationships based on typhoon parameters and calculated water levels due to
storm surge and waves.
This chapter briefly reviews procedures implemented for developing over-
topping and stage-frequency relationships for the study area and presents study
results. Previous chapters give more detailed background on some aspects of the
study. The set of historical storms included in the training set is given in and
discussed in Chapter 2 (Table 1). Storm tracks are provided in Appendix A.
Detailed discussion of the modeling approach is given in Chapter 3.
Storm Surge/Tidal Elevation Relationship
Storm-surge elevations are dependent on water depth as well as intensity and
angle of approach of the storm. The most accurate method for calculation of
36
Chapter 5
Development of Overtopping and Stage-Frequency Relationships
Previous Page
