Risk assessments for debris flows

Increasingly, debris-flow hazard assessments based on largely arbitrary design return periods are being replaced by risk assessments because the inclusion of consequences is ultimately required for sound management decisions. A full quantitative risk assessment of debris flows requires high-quality and well-researched input parameters in order to obtain defensible results. It adds a degree of sophistication that may not be warranted for all applications because of its higher intensity of field and office effort. For high-consequence cases, however, it appears to be an indispensable tool. This chapter details methods that can be applied to assessing debris-flow risk to fixed developments as well as linear facilities, and highlights the various caveats associated with each method.