Exploring the effects of hillslope-channel link dynamics and excess rainfall properties on the scaling structure of peak-discharge

Several studies revealed that peak discharges (Q) observed in a nested drainage network following a run-off-generating rainfall event exhibit power law scaling with respect to drainage area (A) as Q(A) = alpha A(theta). However, multiple aspects of how rainfall-runoff process controls the value of the intercept (alpha) and the scaling exponent (theta) are not fully understood. We use the rainfall-runoff model CUENCAS and apply it to three different river basins in Iowa to investigate how the interplay among rainfall intensity, duration, hillslope overland flow velocity, channel flow velocity, and the drainage network structure affects these parameters. We show that, for a given catchment: (1) rainfall duration and hillslope overland flow velocity play a dominant role in controlling theta, followed by channel flow velocity and rainfall intensity; (2) alpha is systematically controlled by the interplay among rainfall intensity, duration, hillslope overland flow velocity, and channel flow velocity, which highlights that it is the combined effect of these factors that controls the exact values of alpha and theta; and (3) a scale break occurs when runoff generated on hillslopes runs off into the drainage network very rapidly and the scale at which the break happens is determined by the interplay among rainfall duration, hillslope overland flow velocity, and channel flow velocity. (C) 2013 Elsevier Ltd. All rights reserved.