Preprints
https://doi.org/10.5194/egusphere-2023-2695
https://doi.org/10.5194/egusphere-2023-2695
08 Dec 2023
 | 08 Dec 2023

Exploratory analysis of the annual risk to life from debris flows

Mark Bloomberg, Tim Davies, Elena Moltchanova, Tom Robinson, and David Palmer

Abstract. Debris flows are hazardous yet often unrecognised and poorly understood by the public and natural hazards community. Some catchments generate debris flows with average recurrence intervals (ARIs) <10 years, but most debris flow catchments have ARIs ranging from decades to millennia. Consequently, many debris flow catchments pose an underappreciated hazard, especially where there are dwellings on debris flow fans and other depositional areas.

Here, we describe how to use simple and well-accepted methods to:

  • Make a preliminary identification of catchments that are susceptible to debris flows.
  • Estimate the threshold ARI for debris flows in a catchment below which there is an unacceptable annual risk to life for the occupiers of any dwellings.
  • Identify the "window of non-recognition" where debris flows are sufficiently infrequent within a catchment that it is not recognised as susceptible, yet frequent enough that the risk to life exceeds the accepted threshold.
  • Explore the influence of the important parameters driving the annual risk to life from debris flows.

We show that, given precautionary but realistic assumptions about debris flow hazards and the vulnerability of dwellings and their occupants, catchments with no history of debris flow activity can pose an unrecognised and unacceptable risk to life.

Mark Bloomberg, Tim Davies, Elena Moltchanova, Tom Robinson, and David Palmer

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-2695', Anonymous Referee #1, 23 Jan 2024
  • RC2: 'Comment on egusphere-2023-2695', Anonymous Referee #2, 31 Jan 2024
Mark Bloomberg, Tim Davies, Elena Moltchanova, Tom Robinson, and David Palmer
Mark Bloomberg, Tim Davies, Elena Moltchanova, Tom Robinson, and David Palmer

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Short summary
Debris flows occur infrequently, with average recurrence intervals (ARIs) ranging from decades to millennia. Consequently, they pose an underappreciated hazard. We describe how to make a preliminary identification of debris flow-susceptible catchments, estimate threshold ARIs for debris flows which pose an unacceptable risk to life, and identify the "window of non-recognition" where debris flows are infrequent enough that their hazard is unrecognised, yet frequent enough to pose a risk to life.