Physical modeling of baffles influence on landslide debris mobility

Debris flows surge downslope carrying destructive energy and can result in long runout distances. Structural mitigation is commonly installed along the flow path to impede debris flow mobility and protect downstream facilities. An array of baffles is a structural countermeasure frequently designed using empirical methods or prescribed to impede debris flow; nonetheless, its influence on reducing mobility is not well understood. A 5-m-long flume model is used to conduct a series of tests to systematically study the effects of varying baffle height, number of rows, spacing between rows, and degree of transverse blockage on mobility. Froude scaling is adopted to characterize initial upstream conditions. Debris runout, overflow, and frontal velocity reduction resulting from each baffle configuration used are examined. Experimental results reveal that it is imperative to adopt baffle heights taller than the approach flow depth (h) in order to suppress overflow and reduce runout. Adopting 1.5h-tall baffles can reduce runout and peak overflow depth by 19 and 20% compared to short baffles (0.75h), respectively. A single row of baffles is ineffective in reducing frontal debris velocity, whereas increasing the array to three rows leads to 65% reduction in runout and up to 57% reduction in frontal velocity. Increasing spacing between successive rows from 0.25w to 0.5w can reduce runout by up to 37%.