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Insight on the Variable Nature of Channel and Bank-Forming Discharges

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Paper number  032279,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.13824) @2003
Authors:   Andy Ward, Dan Mecklenburg, Dawn Farver, Jon Witter, Anand Jayakaran
Keywords:   Bankfull, Effective Discharge, Sediment, Recurrence Interval, Fluvial Geomorphology

The goal of the paper is to provide insight on why various terms are used to describe the channel forming discharge and how these discharges are related to recurrence interval, sediment transport, channel dimensions, and drainage area. Results are presented of studies by the authors on low gradient streams in Ohio. A review is presented of studies of discharges that are most influential in shaping streams. Historically, there are many examples of stream modifications that paid little attention to the discharges that naturally shape a stream. To some extent this oversight has been alleviated in the last decade by also considering a bankfull or effective discharge. These discharges are sometimes incorrectly identified or evaluated and we have a societal fixation in tying them to a 1 to 2 year recurrence interval. Inadequate attention has been paid to reports in the literature by eminent geomorphologists who provide extensive discussion on the relationship between the effective discharge, bankfull discharge, other discharges, sediment transport, and recurrence interval. For the streams in this study there was close agreement between bank-forming discharges associated with effective discharge and bankfull discharge concepts. All of the streams suggested that the bank-forming discharges are associated with a range of discharges. Calculation of the effective discharge was sensitive to the subdivision of the sediment and discharge data into unequal bin sizes. The bank-forming discharges were primarily related to the transport of the middle 50% of the total sediment load. The recurrence interval of the bank-forming discharges generally ranged from 0.8 to 1.0-years. A study of the frequency of daily discharges that equal or exceed the bank-forming discharges suggests that for these streams these flows occur several times annually and the annual peaks approach is a poor indicator of the actual frequency of the flows. eave the word "Abstract." then type your abstract here. For a new paragraph, do not tab over or indent, just hit the Enter key. It will look like a double space between paragraphs. If your abstract is long, choose a smaller font or let it run onto the next page.

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