PREDICTION OF 1999-SAN JULIAN DEBRIS FLOWS BASED ON DEPENDENT AND INDEPENDENT OCCURRENCES

Abstract

In this paper, a 1-D governing equations proposed by Egashira et al. is put forward first to describe the mechanics of debris-flow. Debris-flow simulations were conducted in order to understand what happens when rainfall occurs to cause numerous landslides on steep river basin, supposing several realistic occurrences in several tributaries. Multiple debris-flow surges were observed in 1999 San Julian debris-flow event, which was simulated in different contexts. The simulated results suggest that the different possible sequences can produce different amounts of sediment volume. Maximum sediment-volume difference between independent and dependent predictions was 0.12×10⁶m³, which is very large and cannot be neglected. This shows that the order of debris flow occurrences should be taken into account for simulating debris-flow behavior at the fan-head.