Event-based high-temporal resolution modeling of streamflow and sediment transport in a flood-prone catchment

To improve hydrological simulation in flood-prone catchments, it is important to capture event-scale dynamics while leveraging long-term records for event selection. In this study, the Soil and Water Assessment Tool (SWAT) was used to simulate event-scale hourly streamflow and sediment transport in a flood-prone steep-slope catchment. Ten events were selected based on their exceedance probabilities within the catchment over a 20-y period, and the model was calibrated and validated on an hourly timescale. Streamflow performance ranged from limited to very good, whereas sediment simulation ranged from limited to good. Peak magnitude and timing deviations further indicated limitations in simulating hourly peak behavior. The model performed better under moist antecedent conditions and low total precipitation than under drier antecedent conditions, suggesting that the performance of sediment transport simulations depends on both antecedent conditions and within-event precipitation characteristics. To enhance model-output interpretation, we applied the sediment yield per unit rainfall erosivity (SYRE) index, which links event sediment yield to rainfall erosivity. A key contribution of this study is the integration of hourly event-based SWAT sediment simulation with the SYRE index to compare rainfall-erosivity-normalized sediment responsiveness across both subbasins and extreme high-flow events in a large, steep mountainous catchment. SYRE revealed persistent high sediment responsiveness in several subbasins, together with event-to-event variability, indicating that sediment response was shaped by both spatial heterogeneity and event conditions. These findings highlight the importance of antecedent conditions, precipitation characteristics, and subbasin-specific properties in high-temporal-resolution modeling for flood and erosion-risk assessment.