ANALYSIS OF WIND‐ AND SHIP‐INDUCED SEDIMENT RESUSPENSION IN DULUTH‐SUPERIOR HARBOR1

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Abstract
Suspended solids and ammonium concentration profiles measured at five locations in Duluth‐Superior Harbor during July‐October 1985 were analyzed to quantify wind and ship effects on sediment resuspension and resulting harbor water quality. Wind components from the SE quadrant correlated strongly with depth‐averaged suspended solids concentrations that were unaffected by ship passage or thermal stratification. Winds from that quadrant have the largest fetch in the harbor. The highest correlation (r2= 0.93) was with the 6‐hour average of the ESE wind velocity component. Multiple linear regression analysis of data from post‐ship passage concentration profiles yielded numerical estimates of settling velocities of 0.08 to 0.25 cm s−1, typical of ship‐resuspended sediments, and vertical eddy diffusivities of 4 to 13 cm2 s1. The results suggest that ambient vertical eddy diffusivities in the harbor are less than 4 cm2 s−1 in the absence of ship passages and with winds less than 5 m s−1 (10 knots).

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