Rainfall-Runoff Event Analysis towards the Understanding of Hydrological Behaviour of a Headwater Catchment in Western Ghats, Karnataka, India – A Case Study

This study investigates the dominant runoff generation mechanisms and flood peak controls in a small forested headwater catchment located in the Western Ghats of South India – an ecologically sensitive and data-scarce mountainous region. Using high‐temporal‐resolution rainfall-runoff event analysis, the research reveals that streamflow response is primarily governed by subsurface flow pathways and saturation‐excess runoff, rather than Hortonian overland flow. Short lag times and low runoff coefficients across events highlight the significance of rapid interflow and shallow groundwater contributions, supporting the applicability of the Variable Source Area (VSA) concept in explaining hydrologic behaviour. Antecedent wetness conditions, quantified through antecedent precipitation and the Catchment Storage Index (CSI), were identified as stronger predictors of flood peaks and saturated area expansion than rainfall intensity or amount. The results emphasize the importance of internal storage dynamics and threshold responses in stormflow generation. The study demonstrates that reliable hydrological insights can be derived through event‐based correlation analysis even with limited data availability. Findings hold important implications for flood forecasting, hydrological modelling, and infrastructure planning, and highlight the need to explicitly incorporate subsurface processes, dynamic contributing areas, and antecedent conditions into modelling frameworks for VSA‐dominated catchments.