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River Bottom Habitats

What are they?

Map of the river bottom
Colored shaded relief map of a portion of the floor of
the estuary off the mouth of Wappinger Creek.
Blue is deeper water; red is shallower water.
Image courtesy of Roger Flood, SUNY Stony Brook.

Underneath the surface of the Hudson River Estuary exists a wide range of river-bottom habitats-from the shallow, muddy bottom in the Tappan Zee and other shallow near-shore areas, to the deep, sandy bottom in the navigation channel that runs north to Albany.

Why are they important?

River-bottom habitats are important for various fish species that spawn or feed on the bottom, for placement of structures such as underwater cables, pipelines, and piers, and for their historical record - there are many ship wrecks on the river bottom, some of which may have great historic values.

Where are they?

The Hudson River Estuary Benthic Mapping Project has mapped much of the physical environment of the Hudson River estuary bottom that extends from New York Harbor to Troy. The major goals of the project are to provide a base map of benthic (river bottom) habitats, to identify areas where sediments collect or erode, and to obtain the detailed information necessary for permitting and regulation of future human activities such as dredging, fishing, and construction projects. This project has produced the first-ever images of the floor of the estuary.

Water depth in Haverstraw Bay
This map shows water depth in a portion
of Haverstraw Bay.
More maps available in PDF, (4.8 MB)

To obtain high-resolution maps, images and descriptions of the river bottom scientists use various sonars to image the river bottom and the layers of sediment beneath the bottom. To interpret the acoustic images in terms of sediment properties scientists have collected and analyzed over 1000 samples of the river bottom sediment for grain size composition and physical properties. To learn more about the surveying technologies go to "Sea Floor Mapping Technology" in the "Links Leaving DEC's website" on the right sidebar.

By combining sediment sample data with acoustic imaging data scientists are able to map the distribution of different sediment types such as mud (silt and clay), sand and gravel over much of the estuary. Scientists are also able to map areas of sediment erosion and deposition on the river bottom. These maps of sediment environment are important when decisions are made about the placement of underwater structures such as pipelines and cables - buried pipelines and cables must be placed in the bottom in areas where they will stay buried. Many of these mapping products are available to the public online at NYSDEC's Benthic Mapper and Mapping Gateway at the NYS GIS Clearinghouse (see the "Links Leaving DEC's website" on the right sidebar). One will need specialized geographic information (GIS) software to view the information found at the Clearinghouse. MapWindow GIS and gvSIG are a couple of free GIS software packages available to the general public (see the "Links Leaving DEC's website" on the right sidebar).

How are they changing?

image of scientists taking a core sample
Scientists take a core sample to look at sediment of
the river bottom.
Image courtesy of Robin Bell, Columbia University.

Many areas of the river bottom change with time as river currents bring in fresh sediment after storms or erode previously deposited sediment. Mapping the river-bottom provides a framework to better understand and manage the resources dependent on these diverse habitats. Sediment samples were analyzed for radio isotope content in order to determine the age of the sediment. Sediment cores were analyzed for lead content, another way of dating the sediment layers. Scientists are able to combine the dated sediment samples with remote sensing sonar data to create maps showing areas of recent sedimentation.

How are we conserving them?

Various state and federal laws help protect the river bottom resource. These include the federal Abandoned Ship Wreck Act of 1987 that establishes government ownership over most abandoned shipwrecks in the country's waters and protects the wrecks from looting, and the federal Endangered Species Act of 1973 designed to protect and recover imperiled species and the ecosystems upon which they depend. Within New York State a body of law called the Environmental Conservation Law established NYSDEC and authorizes its programs to manage New York's marine and coastal resources and administer fish and wildlife laws, carry out sound fish and wildlife management practices, and conduct fish and wildlife research.

Peer-reviewed reports on benthic mapping

Bell, R.E., R.D. Flood, S. Carbotte, W.B.F. Ryan, C. McHugh, M. Cormier, R. Versteeg, H. Bokuniewicz, V.L. Ferrini, J. Thissen, J.W. Ladd, E. A. Blair, 2006, Benthic Habitat Mapping in the Hudson River Estuary, in J. Levinton (editor), The Hudson River Estuary, Cambridge Univ. Press, pp. 51-64.

Carbotte, S.M., R.E. Bell, W.B.F. Ryan, C. McHugh, A. Slagle, F.O. Nitsche , J. Rubenstone, 2004, Environmental change and oyster colonization within the Hudson River estuary linked to Holocene climate, Geo-Marine Letters., 24, 212-224.

Flood, R.D. and R.M. Cerrato, 2010, Scales and Significance of Sediment Variability in the Hudson River, report to the Hudson River Foundation, 83 pages.

Kenna, T.C., F.O. Nitsche, et al, 2011, Evaluation and calibration of a Field Portable X-Ray Fluorescence spectrometer for quantitative analysis of siliciclastic soils and sediments, Journal of Analytical Atomic Spectrometry, 26(2), 395-405.

McHugh, C.M.G., Pekar, S.F., Christie-Blick, N., Ryan, W.B.F., Carbotte, S., Bell, R., 2004. Spatial variations in a condensed interval between estuarine and open marine settings: Holocene Hudson River Estuary and adjacent continental shelf. Geology, 32 (2): 169-172.

McHugh, C.M.G., Pekar, S.F., Christie-Blick, N., Ryan, W.B.F., Carbotte, S., Bell, R., 2004. Spatial variations in a condensed interval between estuarine and open marine settings: Holocene Hudson River Estuary and adjacent continental shelf. Geology, 32 (2): 169-172.

McHugh, C.M.G., S. Pekar, N. Christie-Blick, W. B. F. Ryan, S. Carbotte, R. Bell, 2004, Spatial Variations in a condensed interval between estuarine and open-marine settings: Holocene Hudson River estuary and adjacent continental shelf, Geology, v.32, 169-172.

Nitsche, F.O., Bell, R., Carbotte, S.M., Ryan, W.B.F., Flood, R., 2004. Process-related classification of acoustic data from the Hudson River Estuary. Marine Geology, 209(1-4): 131-145.

Nitsche, F.O., et al., 2005, A seabed classification approach based on multiple acoustic sensors in the Hudson River Esutary, in D.M. FitzGerald and J. Knight (eds) High Resolution Morphodynamics and Sedimentary Evolution of Estuaries: Springer, pp 33-55.

Nitsche, F.O., R. Bell, S.M. Carbotte, W.B.F. Ryan, A. Slagle, S. Chillrud, T. Kenna, R. Flood, V. Ferrini, R. Cerrato, C. McHugh, D. Strayer, 2005, Integrative Acoustic Mapping Reveals Hudson River Sediment Processes and Habitats, EOS 86(24), pp 225-229.

Nitsche, F.O., Slagle, A., Ryan, W.B.F., Carbotte, S., Bell, R., Flood, R., 2011. Chapter 6 - Human impacts on Hudson River morphology and sediments - a result of changing uses and interests. In: R. Henshaw (ed.), Hudson River Environmental History. State University of New York Press, 53-65.

Nitsche, F.O., T.C. Kenna, M. Haberman, 2010, Quantifying 20th century deposition in complex estuarine environment: An example from the Hudson River, Estuarine, Coastal and Shelf Science, 89, 163-174.

Nitsche, F.O., W.B.F. Ryan, S.M. Carbotte, R.E. Bell, A. Slagle, C. Bertinado, R. Flood, T. Kenna, C. McHugh, 2007, Regional patterns and local variations of sediment distribution in the Hudson River Estuary, Estuarine, Coastal and Shelf Science, 71, 259-277.

Pekar, S.F., McHugh, C.M.G., Christie-Blick, N., Jones, M., Carbotte, S.M., Bell, R.E., Lynch-Stieglitz, J., 2004. Estuarine processes and their stratigraphic record: paleosalinity and sedimentation changes in the Hudson Estuary (North America). Marine Geology, 209(1-4): 113-129.

Strayer, D.L., M.M. Malcolm, R.E. Bell, S.M. Carbotte, F.O. Nitsche, 2006, Using geophysical information to define benthic habitats in a large river, Freshwater Biology 51, 25-38.