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Stage discharge estimation using a 1d river hydraulic model and spatially-variable roughness Blair, Timothy

Abstract

Stage-discharge relations (rating curves) are integral to stream gauging, yet the existing empirical calibration methods are expensive, particularly in remote areas, and are limited to low flows. Numerical modelling can provide stage-discharge relations from a single site survey, reducing the overall cost, and can be fit to changing surface conditions. This study explores a one-dimensional model to calculate theoretical stage-discharge relations for four field sites in British Columbia that range in bed stability, bed structure, hydrology and sediment supply. However, due to the non-linear relation between flow and roughness we do not assume the conventional reach-averaged roughness and instead employ a spatially-distributed roughness model. Furthermore, based on local grain size distribution and refined field survey technique, new formulae for wetted perimeter, flow area, and flow depth were developed that eliminate commonly held modelling assumptions and reduce topographic error. The results show (1) good agreement with Water Survey of Canada measurements, (2) distributed roughness provided an improvement over spatially-averaged roughness, (3) spatial variability of the geomorphology within the channel reach leads to shifts in the stage-discharge relations and high sediment amplifies those shifts, and (4) the relations must be re-evaluated following events that mobilize the bed. The method can be used to estimate high flows and flows in remote locations and it does not require calibration.

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Attribution-NonCommercial-NoDerivatives 4.0 International

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