Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2011
Publication Date: 5/1/2012
Publication URL: http://handle.nal.usda.gov/10113/56443
Citation: Fry, B.E., Ward, A., King, K.W. 2012. The frequency of channel-forming discharges in a tributary of Upper Big Walnut Creek, Ohio. Journal of Soil and Water Conservation. 67:173-182. Interpretive Summary: Headwater streams account for greater than two-thirds of all stream miles in any given watershed. Typical rainfall events often result in flows exceeding the streams banks. Quantifying the frequency and magnitude of flows that extend out onto the floodplain is imperative for managing these riparian areas for maximum water quality benefits. We evaluated several locations on a tributary headwater stream located in Upper Big Walnut Creek watershed, Ohio. Thirty-eight percent of the locations studied had flows that extended onto the floodplain for one-third of all measured rainfall events. The findings suggest that the management and environmental benefits of floodplain interaction should be quantified.
Technical Abstract: The goal of this study was to determine the frequency and magnitude of annual out-of-bank discharges in Sugar Creek, a tributary of the Upper Big Walnut Creek, in Ohio. To address this goal: a stream geomorphology study was conducted; measured discharge data at a downstream location were used to develop a calibrated discharge versus recurrence interval relationship; and the HEC-HMS and HEC-RAS simulation models were used to develop out-of-bank discharge recurrence interval relationships for selected locations along Sugar Creek. Much of Sugar Creek was in dynamic equilibrium, and had an extensive floodplain with entrenchment ratios ranging from 2 to 18. At the 8 locations studied, 38% experienced bankfull or larger discharges an average of 12 times per year, with about a 0.2-year recurrence interval for the bankfull discharge. Seventy-five percent of the locations experienced bankfull or larger discharges an average of at least 3 times per year, with about a 0.8-year recurrence interval. All of the locations experienced out-of-bank discharges an average of at least once per year, with the 2-year recurrence interval discharge. The annual out-of-bank discharges at each location ranged from 0.4% to 13% of the average annual flow volume. Based on the results of this study, it was recommended that research be conducted in the Sugar Creek watershed to quantify the water quality benefits of a system in dynamic equilibrium and a well attached active floodplain.