Rainfall can travel from mountain slopes to rivers far faster than expected in mountain catchments

Researchers at the University of Tsukuba have discovered that rainfall can trigger substantial runoff and sediment transport in mountainous regions much faster than previously thought. By monitoring river water levels and precipitation in mountainous catchments, the team found that this rapid response can occur even in catchments with slopes surpassing 500 meters in length.

The study, published in the Journal of Hydrology, analyzed 65 rainfall events across seven sites within the University of Tsukuba's Ikawa Forest in Japan. The findings indicate that rainfall-related effects can propagate from mountain slopes to rivers in as little as 160 minutes, challenging the previous assumption that these responses take longer to develop in steep, rugged terrain.

Such rapid hydrological responses in high-relief mountain catchments are crucial for understanding flood development and sediment-related hazards in steep mountainous regions. However, monitoring these environments is challenging due to intense water flow and sediment movement, which can damage equipment and restrict access to observation sites. Therefore, direct field observations in these high-relief, meso-scale catchments (1–10 km²) remain scarce worldwide.

The study's results could significantly improve the prediction of floods and sediment-related hazards in steep mountainous areas, contributing to better disaster prevention and sustainable land management strategies.