computed for each plan (Figure 56). The RMS is used because squared 

 amplification factors are indicative of wave energy, a more relevant basis for 

 comparison than wave height. In computing the RMS, frequencies lower than 

 0.0025 Hz (400 sec) were not included to avoid domination by the Helmholtz 

 peak common to all plans. 



The existing harbor and all plans show minimum values of the RMS amplifi- 

 cation factor around the middle of Pier 1 and end of Pier 2 (Basins 4 and 10). 

 Thus, these tend to be nodal areas. Another notable feature of the figure is the 

 exceptionally high amplifications at the proposed passenger pier in Plans 1 and 2. 

 Basin 30, representing the proposed barge pier for most plans, was inadvertently 

 omitted in Plan 2 long wave runs. Basin 31, which was very similar to Basin 30 

 in other long wave runs, is used in its place in the long wave summaries in this 

 report. 



Evaluation Against Operational Criteria for Long 

 Waves 



Procedures for evaluating the operational acceptability of different harbor 

 plans subjected to long waves are reviewed in Chapter 4. This study used a 

 variation of the most direct procedure (Seabergh and Thomas 1995). The 

 percent of observations with H slong greater than 10 cm was computed for each 

 basin and plan. However, the range of long wave frequencies was divided into 

 two segments having periods ranging from 30-100 sec and 100-400 sec. The 

 choice of 100 sec as the dividing point was based on an expected sensitivity of 

 barges to periods in the shorter period range and a lower confidence in that range 

 because of the concern that K r may be slightly high. H sUm is calculated as 



B +« = 4 



\ 



*• ampJfi 



^ amp'a 



X Earrayifi) (32) 



where 



N,,N 2 = spectral line numbers in model corresponding to the 

 period range being considered (30-100 sec or 100- 

 400 sec) 



(A-amJkBbariA-w^ana, = amplification factors for i* spectral line in model 



Earrajfi) = spectral energy at array for i* spectral line in model 

 (interpolated from gage data), in units of cm 2 



Amplification factor at the array is needed as a divisor because long waves can 

 easily reflect back to the array. Spectral energy at the array cannot be considered 



80 



Chapter 6 Harbor Oscillations 



