Characterizing the effects of dry antecedent soil moisture conditions, channel transmission losses, and variable precipitation on peak flow scaling

Abstract

Peak discharge to drainage area relationships are widely applied engineering solutions for design flood estimation in ungauged basins. In this study we investigated the effects of antecedent moisture conditions (AMC), rainfall duration, and channel transmission losses on discharge-drainage area power law scaling relationships. The spatial organization of peak discharges were evaluated through coupled surface-subsurface physics based numerical modeling. We take advantage past research and the detailed flexibility of HydroGeoSphere, the numerical modeling platform, to systematically vary AMC and rainfall depths evolving the current understanding of the effects on discharge-drainage area relationships. Channel network dynamics in the Beaver Creek watershed dominated the location of a scale break, or the location where the log-log linear relationship between peak discharge and drainage area is best described by two or more slopes. Single peaked hydrographs and high-quality power law scaling relationships resulted from wet AMC conditions or high precipitation depths. As we reduced the AMC, under low rainfall depths, the hillslope response diverged from the channel response, providing an unorganized system response no longer fitting the power law scaling relationship. Additionally, when initializing the system under losing stream conditions, where the stream channel is assumed unsaturated, a single peaked response ensued whereby the channel and hillslope responded in unison. This study adds to our current understanding of the physical basis of the variability of the scaling structure of peak discharges that is observed in single rainfall-runoff events by investigating the spatial organization of peak discharges under exceedingly dry antecedent soil moisture conditions.