Quantifying the spatial variability of rainfall and flow routing on flood response across scales

The different spatial patterns of hydrologic processes always lead to different flood responses, and this effect varies with environment and scale. In this paper, we evaluate the sensitivity of hydrologic response to the spatial variability of rainfall and flow routing by a variability framework, which explicitly expresses the main features of hydrology in terms of the spatial-temporal variability of rainfall, runoff and flow routing. For a more general conclusion, a stochastic rainfall generator is used as input of the variability framework. We perform the numerical experiments at the Yanduhe Basin and its 64 subcatchments, with area ranging over three orders of magnitude. The results suggest that the sensitivity of hydrologic response to the spatial variability of rainfall depends on the characteristics of rainfall and antecedent soil moisture. The contribution of spatial variability of rainfall reaches the peak in the case of relatively small rainfall event or antecedent dry condition. Influenced by the characteristics of local rainfall, the contribution of spatial variability increases with the subcatchment size at the Yanduhe Basin. The hillslope routing is dominant for slow runoff or small catchment. With the increasing of flow velocity and catchment size, the importance of channel routing significantly increases.