size of the estuarine drainage area, estuary area and volume, riverflow, depth and salinity. In a 
more recent estuarine classification, Engle et al. (2007) updated the Burgess et al. (2004) 
classification scheme to incorporate average air and water temperature and surface and bottom 
water temperature and found that the estuaries clustered into 9 classes. Bricker et al. (in prep.) 
also used a cluster analysis to classify the same estuaries and they found that the estuaries were 
best clustered by estuary depth, tide, ratio of freshwater input to estuary area, temperature, and 
mouth openness, resulting in a classification with 10 classes of estuaries. 
Using the Engle et al. (2007) classification, the estuaries sampled in the Classification 
data set fall into two classes (Alsea and Umpqua in one; and Coos, Tillamook, and Yaquina in a 
second class). In the Bricker et al. classification, the estuaries sampled in the Classification data 
set fall into two classes; however, Alsea, Tillamook, Umpqua and Yaquina are in one class and 
Coos is in another. The Oregon estuaries sampled in the NCA data set fall into 3 classes in the 
Engle et al. (2007) classification with 8 of the 11 classified as within one class, while in the 
Bricker et al. classification these same estuaries fell into 2 classes with 9 of the 11 being in the 
same class. 
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