Date Awarded


Document Type


Degree Name

Master of Arts (M.A.)


Virginia Institute of Marine Science


Landsat images are analyzed to investigate the causes of turbidity variations in lower Chesapeake Bay surface water. Visual analysis and image enhancement are used in association with optical film density data obtained along selected Bay transects. The optical density data of all images, inversely related to surface turbidity, are used to produce residual turbidity profiles showing turbidity above and below average conditions. meteorological conditions have Images with similar tidal or their residual optical density data averaged to identify probable causes of above average turbidity levels. Freshwater discharge does not directly contribute suspended sediment to Chesapeake Bay, except from the Potomac River during times of high freshwater flow. Much of the detected surface turbidity is associated with resuspension by tidal currents. Flood currents cause higher surface turbidity along the Eastern Shore frorn the Bay mouth to off the Rappahannock River mouth. High ebb-related turbidity occurs north of the Rappahannock River and in the western half of Chesapeake Bay south of Wolf Trap Shoals. Currents during spring tide produce higher surface turbidity south of the Rappahannock River than currents during other portions of the lunar cycle. Strong wind causes greater surface turbidity than low wind except when wind direction opposes tidal currents. A large fetch (20 km) parallel to wind direction results in higher surface turbidity downwind. A correlation exists between surface turbidity and water depth. Surface turbidity is lower in deeper water due to the weaker effect of tidal and wind resuspension. Resuspension of bottom sediment affects surface in waters as deep as 40 feet.



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