wave field sufficient to significantly perturb the near-bottom 

 pressure field. A summary of the data provided by the gage is 

 shown in Figure 3-91. These plots show the results of simple 

 spectral analysis of near-bottom pressure. Only the higher 

 frequency components representing perturbations in hydrostatic 

 pressure associated with the wind-driven surface wave field were 

 plotted, with variations associated with the tidal system not 

 represented. 



The spectral plots clearly show the effects of Hurricane 

 Gloria on the surface wave-associated pressure field. Beginning 

 at approximately 1215 EDST on 27 September, the amplitude of 

 wave-associated bottom pressures progressively increased to a peak 

 near 1415 EDST, approximately coincident with the observed minimum 

 in barometric pressure (Figure 1-3) . As previously noted, winds 

 during this period were primarily from the south to southeast 

 directions providing sufficient fetch to allow generation of 

 significant surface wave energy. After this peak occurred, the 

 amplitude of the surface wave-associated pressure perturbation 

 progressively decreased coincident with decreasing wind speeds and 

 a general shift in direction from the south to the southwest and 

 eventually northwest. These data indicate that significant surface 

 wave generation and associated pressure and velocity perturbations 

 produced by the passage of Hurricane Gloria were essentially 

 confined to the immediate storm period. Beyond this time, the 

 sediment-water interface was effectively isolated from surface wave 

 effects by the overlying water column. 



3.7.5 Suspended Material Characteristics 



Prior to the passage of Hurricane Gloria, near-bottom 

 suspended material concentrations in the vicinity of the deployment 

 point at NLON displayed ah average value of approximately 2 mg/1 

 (Figure 3-92) . Previous deployments near this site showed that 

 concentrations vary regularly over each tidal cycle (Bohlen, 1982) . 

 This signature, although weak, appeared to be present in the 

 pre-storm record. The onset of Gloria produced a significant 

 perturbation in near-bottom concentrations with peak values 

 increased by more than a factor of eight. This perturbation was 

 relatively short-lived, however, and essentially confined to the 

 immediate stoirm period. This response and the coincidence with 

 the period of maximum surface wave generation suggests that the 

 increase in near-bottoitL suspended materials resulted primarily from 

 resuspension of materials from the sediment-water interface under 

 the combined effects of wind wave-induced velocities and the tidal 

 stream. As noted above, both of these factors decreased sharply 

 following storm passage, the waves decaying due to variations in 

 the surface wind field and tidal velocity decreasing due to 

 storm-associated perturbations in the local tidal system. In the 

 absence of these forcing functions, the high settling velocities 

 characterizing the reworked materials residing along the 

 sediment-water interface favored a rapid decay in suspended 



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