A Model for Debris accumulation and Mobilization in Steep Mountain Streams

1988

8 Abb., 17 Lit. Ang.

Unselbständiges Werk

8208

200026046

Previous work on the initiation of debris flows has emphasized the roles played by material strength, stream gradient, and fluid pressure, but in most published models the friction angle of the channel material is assigned some characteristic or constant value. The model presented here retainsgradient and pressure as variables, and considers the probable changes in (For mel) and hydraulic conductivity, K, of channel debris over time. Preliminary results from the Howe Sound area in southwest British Columbia suggest that stream reworking may lead to small increases in (Formel) and large increases in K, rendering debris more stable with time. This is partially offset by a local increase in channel gradient as debris accumulates. These factors favour the growthof large, marginally stable debris deposits, and may lead to high-magnitude, l ow frequency debris torrents in channels not steep enough to produce torrents directly from hillslope failure events.