EXECUTIVE SUMMARY (continued) 



approximately 1 m or less for the other three seasons. Maximum significant wave heights 

 were roughly 3 m in summer, compared to 6 m in winter, and 7 m in spring and fall. 



Quantitative analysis of storm waves revealed 72 events during the 3.4-year analysis 

 period that had significant wave heights between 3 and 4 m; average durations for these 

 wave events were only 6 to 8 hrs. Wave heights in the range of 5 to 6 m were observed 

 only 22 times with average durations of less than 3 hrs. 



The wave records from March through May 1996 exhibited nine storm events 

 attaining significant wave heights greater than 2 m, with one reaching 5.8 m. This storm 

 activity was similar to that during other recent years, and sufficient for analysis of storm- 

 generated currents as they affect bottom sediment resuspension. 



The three consecutive deployments of moored instrumentation at the PDS yielded 

 nearly complete records of near-bottom currents, water temperature, pressure, and relative 

 turbidity over the period from late February to mid-May 1996. Hourly averaged near- 

 bottom current speeds during the measurement period ranged from to approximately 

 0.4 knots (~20 cms" 1 ), with the majority of the variability occurring at periods of 

 approximately 12 hr in association with the semi-diurnal tide. Tidal harmonic analysis of 

 the current velocity data revealed that the amplitude of the M 2 semi-diurnal tidal current is 

 weak (approximately 3 cm-s" ), but significantly stronger than all other tidal constituents. 



The mean current speed for each of the three deployments was very consistent (7.0 

 ±0.4 cms" 1 ), but the mean direction varied greatly among the deployments, presumably 

 due to rough topography (e.g., boulders and rock ledges) in close proximity to the moored 

 instrumentation. Analysis of residual currents (after the mean current and the tidal 

 currents had been removed from the observed records) revealed that storms had almost no 

 effect on hourly averaged near-bottom currents at the PDS. 



Time-series measurements of near-bottom turbidity during the 78-day measurement 

 period were acquired using optical sensors at levels of 33 and 81 cm above the seafloor. 

 Both sensors provided excellent quality data (with no appreciable biofouling) such that 

 small turbidity fluctuations above a consistently low background level could be 

 distinguished. Near-bottom turbidity data acquired during the nine storm events having 

 significant wave heights greater than 2 m (from late February through mid-May 1996) 

 revealed that substantial quantities of ambient bottom sediments were resuspended during 

 two storms having maximum significant wave heights in excess of 3 m. However, 

 sediment resuspension was minimal or nonexistent for seven other storms having maximum 



