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BANKFULL DISCHARGE RECURRENCE INTERVALS AND REGIONAL HYDRAULIC GEOMETRY RELATIONSHIPS: PATTERNS IN THE PACIFIC NORTHWEST, USA 1
Author(s) -
Castro Janine M.,
Jackson Philip L.
Publication year - 2001
Publication title -
jawra journal of the american water resources association
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.957
H-Index - 105
eISSN - 1752-1688
pISSN - 1093-474X
DOI - 10.1111/j.1752-1688.2001.tb03636.x
Subject(s) - ecoregion , streams , hydrology (agriculture) , vegetation (pathology) , channel (broadcasting) , environmental science , precipitation , physical geography , geology , geography , meteorology , medicine , computer network , ecology , geotechnical engineering , engineering , pathology , computer science , electrical engineering , biology
The model bankfull discharge recurrence interval (annual series) (T a ) in streams has been approximated at a 1.5‐year flow event. This study tests the linkage between regional factors (climate, physiography, and ecoregion) and the frequency of bank‐full discharge events in the Pacific Northwest (PNW). Patterns of Ta were found to be significant when stratified by EPA Ecoregion. The mean value for T a in the PNW is 1.4 years; however, when the data is stratified by ecoregion, the humid areas of western Oregon and Washington have a mean value of 1.2 years, while the dryer areas of Idaho and eastern Oregon and Washington have a mean value of 1.4 to 1.5 years. Among the four factors evaluated, vegetation association and average annual precipitation are the primary factors related to channel form and T a . Based on the results of the T a analyses, regional hydraulic geometry relationships of streams were developed for the PNW, which relate variables, such as bank‐full cross‐sectional area, width, depth, and velocity, to bankfull discharge and drainage area. The verification of T a values, combined with the development of regional hydraulic geometry relationships, provides geographically relevant information that will result in more accurate estimates of hydraulic geometry variables in the PNW.