On the West Coast, the large tidal amplitude experienced over much of the 
region means that a large proportion of total estuarine area is intertidal. For example, 
intertidal habitat constitutes 52% of the estuarine area averaged over all Pacific 
Northwest estuaries, and can constitute as much as 90% in some systems (e.g., Netarts 
Bay; Lee et al., 2006). The initial development of methods and indicators for 
assessment of condition in the NCA were for sampling of subtidal habitats within 
estuaries of the Atlantic and Gulf coasts. Because the Western component of the NCA 
began as a pilot program, there was an opportunity to test development of a variety of 
modified methods and additional indicators for assessment of condition in the extensive 
estuarine intertidal zones prevalent in West Coast estuaries. 
Therefore a pilot assessment of the intertidal habitat of the states of Washington, 
Oregon, and California was carried out in the summer of 2002. This report provides a 
technical summary of the data from this assessment. 
2.0 Methods 
Methods for the 2002 intertidal survey were in general the same as those 
developed for the EPA National Coastal Assessment (Nelson et al., 1999), with 
modifications to reflect the intertidal nature of the resource being assessed. Because 
of the intertidal focus of the survey, water quality and fish tissue samples were omitted 
while vegetational-quadrat and transect samples were added. 
2.1 Sampling Design 
The target resource assessed was the intertidal zone of the states of 
Washington, Oregon and California, with the exception of the estuarine portion of the 
Columbia River. The Columbia was extensively sampled by EMAP surveys conducted 
in 1999, 2000, and 2001, and additional sampling was deemed to be redundant. 
The sample frame is a map defining the target resource. The principal map 
coverage used to develop the 2002 intertidal GIS data layer that was the sample frame 
was the National Wetlands Inventory (NWI) in Arclnfo format. An Arclnfo coverage of 
San Francisco Bay baylands, created by the San Francisco Estuary Institute (SFEI), 
was selected as the map source in the San Francisco Bay area. In some cases, digital 
coverage was lacking, and hard copy maps were scanned and georeferenced, and 
estuarine polygons were hand digitized. 
In order for a polygon to be included in the sample frame coverage for all areas 
except San Francisco Bay (see below), the polygon had to have the following attributes: 
it had to be classified as intertidal, and not classified as hard substrate, high marsh, 
diked, or artificial substrate. Several codes within the NWI coverages were interpreted 
as follows: ‘irregularly exposed’ was interpreted as below Mean Lower Water, and 
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