Seonjun Choi, Tomohiro Tanaka, Kazuaki Yorozu, Yasuto Tachikawa
Received 22 July, 2025
Accepted 30 September, 2025
Published online 25 March, 2026

Seonjun Choi¹⁾, Tomohiro Tanaka²⁾, Kazuaki Yorozu²⁾, Yasuto Tachikawa¹⁾

1) Graduate School of Engineering, Kyoto University, Japan
2) Disaster Prevention Research Institute, Kyoto University, Japan

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.

[Full Text]

Copyright (c) 2026 The Author(s) CC-BY 4.0