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	A multi agency project funded by US EPA's STAR Program

Defining coastal margin segments

The challenge was to divide the approximately 8000 linear kilometers (about 5000 miles) of US Great Lakes coastline into sampleable units. As a first step, we divided the entire coastline into discrete segments such that every meter of coast was part of one and only one segment.

We based these coastline segments on streams flowing into the lakes. Geographic information systems (GIS) were used to locate 2nd order (Strahler stream order) and larger streams. Then the coastline was divided so that segment endpoints were midway between adjacent streams. Thus, each segment contained only one such stream.

Next we needed to associate these coastal segments with land-based environmental factors that might be affecting them. This was accomplished by using digital elevation models (DEMs) to delineate the runoff areas for each segment. These runoff areas are essentially the watersheds of the coastal margin segments.

The resulting 762 "segment sheds" encompass the entire US Great Lakes coast from Grand Portage, Minnesota, to Watertown, New York.