Knowra Debris flow Debris flow A rapid downslope flow of water mixed with abundant sediment, rocks, and sometimes organic material. Its dense, poorly sorted mixture can carry large clasts and damage areas far from its source.
Pore-water pressure : The pressure exerted by water within the pores of soil or rock. Rising pore-water pressure reduces grain contact and can help a slope mixture begin flowing.
Mass wasting : The downslope movement of rock, soil, or sediment under gravity. Debris flows are one rapid form of gravity-driven mass wasting.
Debris-flow hazard : The potential for debris flows to cause harm to people, infrastructure, or ecosystems. Flow speed, reach, and impact make hazard assessment central to managing exposed areas.
Intense rainfall : Rain falling at a high rate over a short period or a limited area. Intense rainfall can saturate slopes, raise pore-water pressure, and trigger flows.
Montecito debris flows : The destructive debris flows that struck Montecito, California, in January 2018. The event followed wildfire and intense rainfall, illustrating how hazards can compound.
Shear strength : A material's resistance to deformation by forces acting parallel to a surface. Debris flows begin when downslope stress overcomes the sediment's shear strength.
Landslide : The movement of rock, earth, or debris down a slope. The term covers slope movements that may transform into debris flows.
Debris-flow warning system : A system that detects conditions or signals associated with imminent debris flows. Rain gauges and flow sensors can provide warning when conditions favor rapid flows.
Snowmelt : The conversion of snow into liquid water as temperatures rise or energy is supplied. Rapid snowmelt can supply water that mobilizes loose sediment on steep terrain.
Armero tragedy : The 1985 destruction of Armero, Colombia, by lahars from Nevado del Ruiz. The disaster shows how volcanic debris flows can travel far beyond a crater.
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