REMOTE SENSING AND MAPPING OF COASTAL WETLANDS 
by Robert B. McEwen 
U.S. Geological Survey 
Reston, Virginia 
ABSTRACT 
The U.S. Geological Survey conducted & research project in the vicinity 
of Sapelo Island, Georgia, to investigate procedures for interpreting, 
delineating, and mapping coastal wetlands using remote sensing and photo- 
grammetric techniques. The study area contains a variety of coastal marsh 
conditions, from saline to brackish, and extends from a maînland river 
through sea island marshes to the Atlantic Ocean. Orthophotoquads were 
prepared at 1:10,000 scale with a format of 2.5 minutes of latitude and 
3.75 minutes of longitude. Coastal wetland boundaries and species associ- 
ations were interpreted from color infrared photographs and delineated on 
the orthophoto base. The primary objective is to evaluate the accuracy, 
time, and cost for mapping coastal wetlands. This paper describes some of 
the legal, engineering, and cartographic criteria that must be satisfied by 
the image interpretation. The results should be of value to Federal and 
State agencies with responsibilities for mapping or regulating the coastal 
zone. 
INTRODUCTION 
This paper has been adapted from an earlier publication, "Coastal Wetland 
Mapping," by Robért B. McEwen, William J. Kosco, and Virginia P. Carter. Some 
clarifications have been inserted and new information related to coastal mapping 
has been added. The specific techniques of vegetation analysis from imagery are 
not included; rather the intent is to illustrate the legal, engineering, and 
cartographic criteria which must be satisfied by the image interpretation. 
With the increased environmental interest in the coastal zone, there 
are many published papers on applying remote sensing to wetland interpre- 
tation. Ownership and use of riparian lands in the coastal zone of the 
United States is adjudicated according to several State and Federal laws, 
and the regulation of land use is increasing to control development. The 
U.S. Geological Survey (USGS) has evaluated the requirements for wetland 
delineation on 1:24,000-scale standard topographic maps and followed the 
progress of other projects at larger scales. The USGS works closely with 
the National Ocean Survey (NOS), which has primary responsibility for coastal 
navigation charts, geodetic control surveys, and tidal surveys. The two 
agencies are preparing a Coastal Mapping Handbook and are cooperating in the 
publication of topographic/bathymetric maps. 
The coastal zone is not precisely defined but is generally agreed to extend 
at least from the national seaward boundary to coastlands under the influence of 
the sea. For different purposes, the zone has been traditionally mapped by both 
USGS and NOS, as well as the U.S. Army Corps of Engineers and the coastal States.