This study proposes slope surface flow monitoring via time-lapse cameras as a novel validation metric for hydrological modeling in steep forested catchments. We evaluated a kinematic wave-based distributed hydrological model (1K-DHM) using both river discharge and slope surface flow duration observed during flood events. While 1K-DHM reproduced hydrographs well, it significantly overestimated slope surface flow duration, indicating structural limitations in representing vertical infiltration. To address this, we incorporated a Green-Ampt (GA) percolation module into 1K-DHM. The revised model (1K-DHM-GA) improved both hydrograph reproduction (the Nash-Sutcliffe Efficiency: 0.848, RMSE: 0.021 m3/s) and slope surface flow duration agreement (Jaccard Index: 0.745). Results demonstrate that integrating vertical percolation improves runoff simulation and that slope surface flow monitoring provides valuable constraints for evaluating model structure under equifinality.
Choi et al. (Thu,) studied this question.