Area 2 - The Newburgh Bay Region: The 18.5 km Newburgh Bay segment extends from Storm King Mountain in the south to Wappingers Creek in the north (41° 26' N to 41° 36' N). In this reach river morphology changes from the narrow, deep channel associated with the Hudson Highlands, to the open expanse of Newburgh Bay, to narrow again north of Danskammer Point. The river in this area alternates between saline and freshwater flow during the year. The region is dominated by human activities, and the effects of bridge construction, the path of a cable crossing, and numerous dump sites are clearly imaged in the data. Recent deposition is closely associated with flow obstructions by natural (e.g., Diamond Reef) and man-made (e.g., Beacon-Newburgh Bridge) features. The southern portion of this region appears to be less impacted by recent human activities and contains Revolutionary War structures and records of ancient storms.

Area 3 - Kingston - Saugerties Region: This 18.5 km region extends from Kingston at Esopus Creek to Saugerties at Rondout Creek (41° 55' Nto42° 05' N). The river is freshwater here, and is dredged in some stretches. This region has been affected by large sediment inputs from Esopus Creek and Rondout Creek, which drain east from the Catskill Mountains. Alarge coarse sediment influxmaybe,inpart, responsible for the numerous large sand waves imaged in the area (color plate 2). Much of the modern hydrodynamics and the distribution of recent sediments may be linked to deepening of the western channel. This portion of the river includes Tivoli Bays, a component of the Hudson River Reserve (part of the National Estuarine Research Reserve System). As part of our study a pilot program in shallow water geophysics which included ground penetrating radar was carried out within Tivoli Bay.

Area 4 - Stockport Flats Region: The 18.5 km Stockport Flats survey area extends from the City of Hudson in the south to the town of New Baltimore in the north (42° 15' N to 42° 25' N). The section is tidal fresh water, and also includes the Stockport Flats National Estuarine Research Reserve site. This segment of the river has been impactedby 150 years of dredging, disposal of dredge spoils and the

Figure 5.2. Cartoon showing the operation of a multi-beam echosounder. Sound is transmitted in a swath across the ship track, and the returning sound is analyzed to provide a series of water depths across the profile. Figure from Konsgburg-Simrad, Inc.

building of dredge spoil islands such as the Stockport Middle Ground. Much of the deeper channel is characterized by large sand waves. The present flow regime inferred from channel morphology and bedform distribution appears to be largely controlled by dredging.

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