Investigating the effects of spatial heterogeneity of multi-source profile soil moisture on spatial–temporal processes of high-resolution floods

Abstract

Reliable spatial–temporal simulation and forecast of flood are crucial for accurate flood control. Profile soil moisture (PSM) is a key intermediate variable in rainfall-runoff transformation, its spatial heterogeneity affects the spatial–temporal processes of floods. However, soil moisture data in the current flood modeling researches are only the intermediately simulated values that lack spatial validation, how spatial heterogeneity in soil moisture affects high-resolution flood processes is still unclear. In contrast, soil moisture data derived from satellites are spatial observed values that can better represent real spatial distribution. This study is first to incorporate satellite-based data and hydrological modeled data to identify the effects of different spatial patterns of profile soil moisture on spatial–temporal processes of floods at 1 km × 1 km resolution. The distributed hydrological model (DDRM) and the European Space Agency Climate Change Initiative (ESA CCI) products are chosen to provide different PSM spatial patterns, under which, the DDRM is used to investigate corresponding spatial–temporal processes of floods. Four modeling scenarios (two DDRM-only scenarios and two assimilation scenarios) in two humid and one semi-arid catchments are set to see the different effects, and the spatial–temporal statistical analysis and the semi-variogram method are used to identify the spatial heterogeneity. Results indicate that both PSM and runoff show strong spatial heterogeneity with the values of C/(C0 + C) in the semi-variogram method higher than 0.8; for different periods, the decrease of spatial heterogeneity in PSM corresponds to the decrease of spatial heterogeneity in runoff; for different scenarios, soil moisture storage capacity (SMC) affects spatial heterogeneity of runoff more in the semi-arid catchment, and the change of sensitive parameters of spatial soil moisture is the main driver to change the spatial heterogeneity of runoff. The findings of the study would enhance the development of refined modeling of floods, and have practical implications for flood risk management and early flood warning systems.