Aim of the study:
Near-surface lateral flow (interflow) is an important component of runoff generation in hilly catchments; however, its direct identification in the field remains methodologically challenging. In many hydrological studies, this process is inferred indirectly from hydrograph analysis or numerical modelling, while field-based observations linking soil moisture dynamics, soil stratification, and event-based water balance are scarce. This study presents results from a small, forested hillslope catchment and aims to identify near-surface lateral flow using a combined, measurement-oriented field approach.

Material and methods:
Multi-depth soil moisture monitoring under undisturbed soil conditions was integrated with a controlled, plot-scale rainfall-infiltration experiment, enabling joint interpretation of vertical soil water storage dynamics and event-based water balance components.

Results and conclusions:
The measurements showed rapid wetting in the upper soil layers, while deeper layers exhibited delayed and attenuated responses. Event-based water balance calculations indicated that a substantial fraction of the applied water could not be detected in vertical soil water storage changes within the monitored profile, pointing to lateral redistribution within the near-surface soil layers. The results demonstrate that the applied measurement concept is effective for field-scale identification of near-surface lateral flow using indirect but physically interpretable indicators. The study highlights the importance of combining multi-depth soil moisture monitoring with controlled infiltration experiments to improve process-based understanding and representation of runoff generation mechanisms in forested hillslope catchments.