Title:
Linking Shifts in Historic Estuarine Vegetation to Salinity Changes Using a GIS
Linking Shifts in Historic Estuarine Vegetation to Salinity Changes Using a GIS
Author(s)
Smith, Carrie
Alber, Merryl
Chalmers, Alice
Alber, Merryl
Chalmers, Alice
Advisor(s)
Editor(s)
Hatcher, Kathryn J.
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Abstract
There are anecdotal reports that upstream
water withdrawals over the past 50 years have altered
the salinity structure of coastal Georgia estuaries.
Since few consistent salinity records exist, it may be
possible to use shifts in vegetation to document salinity
change. The purpose of this study was to use aerial
photographs and GIS analysis to determine if the
location of the brackish water interface in two Georgia
estuaries has changed. Current vegetation maps of the Satilla and Altamaha estuaries were constructed from 1993 USGS DOQQs. Vegetation was outlined and
classified as Juncus roemerianus, brackish marsh, fresh marsh, salt marsh, or other. Historic vegetation maps were similarly constructed from 1:77000-scale color infrared photographs taken in 1974 and 1:24000-scale
black and white photographs taken in 1953. Change
maps between all years were constructed for each river.
In the Altamaha River, 6,786 hectares of marsh area
were mapped, of which 77% did not change between
1953 and 1993; Of the 10,205 hectares of marsh area mapped in the Satilla, 87% did not change between 1953 and 1993. Shifts in Juncus constituted the primary vegetation change in both estuaries (95% in the
Satilla and 87% in the Altamaha). However, these
changes in Juncus do not necessarily reflect changes in
estuarine salinity, indicating a need for further
investigation of Juncus interactions in these systems.
Sponsor
Sponsored and Organized by: U.S. Geological Survey, Georgia Department of Natural Resources, Natural Resources Conservation Service, The University of Georgia, Georgia State University, Georgia Institute of Technology
Date Issued
2001-03
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Resource Type
Text
Resource Subtype
Proceedings