Author(s): Kwan Tun Lee; Jen-Kuo Huang; Yi-Ru Chung
Linked Author(s):
Keywords: Runoff nonlinearity; Watershed scale; Kinematic-wave-based geomorphologic IUH
Abstract: The nonlinear properties of runoff response induced by storm magnitude and watershed size are discussed. For nonlinearity in storm magnitude aspect, the analysis of hydrological records at three study watershed in Taiwan illustrates the intrinsic nonlinear transform in rainfall-runoff procedure. The using of linear hydrological models (unit hydrograph and linear reservoir models) and nonlinear ones (variable instantaneous unit hydrograph and kinematic-wave based geomorphic instantaneous unit hydrograph models) for unit hydrology derivation display that a high-intensity rainfall will result in greater peak discharge and shorter time to peak. A low-intensity rainfall leads to opposite results. This is contradictory to the concept in conventional hydrology that a unique unit hydrograph can be specified for a watershed. For nonlinearity in watershed size aspect, the effects of watershed scale and of storm magnitude are investigated by surveying the variation of scaling exponent in the widely-used power-law function. The results show that the runoff response is tended to become more nonlinear as watershed scale increasing. The same trend can also be obviously observed when a watershed is subjected to small magnitude rainfall input. The upstream runoff contributing condition and the partial storm area coverage would be the reasons for such results. The critical transition threshold area that translates runoff response from linearity to nonlinearity is also detected for study watersheds.
Year: 2013