ABSTRACT
Debris žows are geophysical phenomena intermediate in character between rock avalanches and žash žoods. ›ey commonly originate as water-laden landslides on steep slopes and transform into liqueŸed masses of fragmented rock, muddy water, and entrained organic matter that disgorge from canyons onto valley žoors. Typically including 50%–70% solid grains by volume, attaining speeds >10 m/s, and ranging in size up to ∼109 m3, debris žows can denude mountainsides, inundate žoodplains, and devastate people and property (Figure 43.1). Notable recent debris-žow disasters resulted in more than 20,000 fatalities in Armero, Colombia, in 1985 and in Vargas state, Venezuela, in 1999.
