Uncertainty of bankfull discharge estimations

Recently, public regulatory agencies have expressed concern over the general condition of streams and stream channels within rural and non-rural watersheds. Their concerns have centered around providing improvements to the physical condition, water quality effectiveness and terrestrial and aquatic habitat values of degraded stream channels. Accordingly, the engineering community is faced with the task of providing remedial repair design recommendations to facilitate these improvements; however, concise and universally accepted methods for providing these design recommendations currently do not exist. In this paper, the relative uncertainty in determining the bankfull discharge for gaged and ungaged watersheds is quantified. Based on the results, the use of hydraulic geometry relationships currently used by engineers to predict the desired stream channel restoration design parameters will be assessed.