Appendix C: Classification of Oregon Estuaries 
Of the estuaries that were sampled as part of the Classification and NCA data sets, the 
number of classes of estuaries (or types) depends upon the scale of the classification system as 
well as the classification system utilized (see Table C.l). Of the seven estuaries sampled by 
WED in 2004-2005 which form the Classification data set, five were also included in a NOAA 
classification scheme, with 4 estuaries classified as “river dominated with straits and terminal 
bay”, and 1 estuary classified as “coastal embayment - v-shaped and semienclosed.” Lee et al. 
(2006) classified all seven of the estuaries sampled in the Classification effort as “drowned river 
valley” and Bottom et al. (1979) classified 6 of them as “partially mixed” and the 7 th (Coos) as 
“well mixed.” For the Oregon estuaries sampled as part of the NCA effort, the NOAA 
classification would define eight as “river dominated with straits and terminal bay”; one as “river 
dominated with salt wedge” (Columbia), one as “coastal embayment” (Coos), and one as 
“lagoon” (Netarts). 
Quinn et al. (1991) classified West Coast estuaries based on their relative susceptibility to 
nutrient pollution, defined as an estuary’s capability to concentrate dissolved and particulate 
pollutants. In their 1991 study, Quinn et al. classified the estuaries by dissolved concentration 
potential (DCP), which is the ability of the estuary to concentrate dissolved substances, and 
particle retention efficiency (PRE), which is a measure of the ability to retain suspended 
particulates within the estuary. In this classification system, 8 Oregon estuaries (including Alsea, 
Coos, Nehalem, Netarts, and Siletz, Siuslaw, Tillamook, and Yaquina) classified as having 
“high” DCP and “low” PRE. Umpqua Estuary classified as “medium” (near border of high) 
DCP and “low” PRE, while the Columbia River Estuary had “low” DCP and “low” PRE. All of 
the Oregon estuaries classified as being in the medium category of nitrogen concentrations 
(estimated using the loadings and DCP). 
Burgess et al. (2004), Engle et al. (2007), and Bricker et al. (in prep.) classified estuaries 
of the United States using statistical cluster analysis of physical and hydrologic variables to 
determine the response of estuaries to nutrient loading. The Burgess et al. (2004) classification 
included physical and hydrologic parameters including estuarine area, estuary drainage area, area 
of mixing, seawater and tidal fresh portions of the estuary, tide, overflow, estuary volume, tidal 
prism volume, salinity, depth, DCP and PRE. The primary variables contributing to the 
separation of 11 clusters (or classes of estuaries) in the Burgess et al. (2004) classification were 
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