Sediment Processes and Bottom Environments
In order to design and implement a science-based management policy for the Hudson River Estuary, the New York State Department of Environmental Conservation (DEC) launched the Hudson River Estuary Benthic Mapping Project as part of their broader Hudson River Estuary Program. Through this project, the entire 240km (145 miles) length of the Hudson River Estuary has been mapped from the New York Harbor to the town of Troy, New York.
The Hudson River Estuary and areas of potential erosion and deposition that were identified by the Bottom Mapping. The inset map shows the extent of the whole Hudson River watershed (F. Nitsche).
This effort represents the first time an entire estuarine or river system has been mapped in such detail. The major goals of the project were 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 construction projects.
To obtain high-resolution maps, images and descriptions of the river bottom we used a combination of multibeam bathymetry, sidescan sonar and sub-bottom profiling. To validate the various acoustic data we collected 410 sediment cores and 600 grab samples of the river bottom that were analyzed for grain size composition and physical properties. A small number of the samples were also gamma-counted to determine the presence of cesium-137 and beryllium-7.
Based on grain-size analyses and backscatter acoustic data we were able to map the distribution of different sediment types such as mud (silt and clay), sand and gravel throughout the estuary. After combining all available data we identified signs of sediment erosion and deposition on the river bottom, as well as evidence of dynamic sedimentary regimes such as sediment wave fields, scour pools and debris flows.
This integrated analysis of multiple, complementary datasets provides powerful insights into the dynamics of the Hudson River estuarine system that would have been impossible using any single method.
The benthic mapping project is funded by the New York State Department of Environmental Conservation with funds from the Environmental Protection Fund through the Hudson River Estuary Program.
The project is conducted in collaboration with:
Stony Brook University
Institute for Ecosystem Studies
Queen College, City University of New York
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 and D. Strayer, "Integrative acoustic mapping reveals Hudson River sediment processes and habitats," EOS, Transactions, American Geophysical Union
, 2005, 86(24): 225, 229.