TY - JOUR
T1 - Simple rules to minimise exposure to coseismic landslide hazard
AU - Milledge, David G.
AU - Densmore, Alexander L.
AU - Bellugi, Dino
AU - Rosser, Nick J.
AU - Watt, Jack
AU - Li, Gen
AU - Oven, Katie J.
PY - 2019/4/17
Y1 - 2019/4/17
N2 - Landslides constitute a hazard to life and infrastructure and their risk is mitigated primarily by reducing exposure. This requires information on landslide hazard on a scale that can enable informed decisions. Such information is often unavailable to, or not easily interpreted by, those who might need it most (e.g. householders, local governments and non-governmental organisations). To address this shortcoming, we develop simple rules to minimise exposure to coseismic landslide hazard that are understandable, communicable and memorable, and that require no prior knowledge, skills or equipment to apply. We examine rules based on two common metrics of landslide hazard, (1) local slope and (2) upslope contributing area as a proxy for hillslope location relative to rivers or ridge crests. In addition, we introduce and test two new metrics: the maximum angle to the skyline and the hazard area, defined as the upslope area with slope > 40° from which landslide debris can reach a location without passing over a slope of < 10°. We then test the skill with which each metric can identify landslide hazard - defined as the probability of being hit by a landslide - using inventories of landslides triggered by six earthquakes that occurred between 1993 and 2015. We find that the maximum skyline angle and hazard area provide the most skilful predictions, and these results form the basis for two simple rules: "minimise your maximum angle to the skyline" and "avoid steep (> 10°) channels with many steep (> 40°) areas that are upslope". Because local slope alone is also a skilful predictor of landslide hazard, we can formulate a third rule as "minimise the angle of the slope under your feet, especially on steep hillsides, but not at the expense of increasing skyline angle or hazard area". In contrast, the upslope contributing area has a weaker and more complex relationship to hazard than the other predictors. Our simple rules complement but do not replace detailed site-specific investigation: they can be used for initial estimations of landslide hazard or to guide decision-making in the absence of any other information.
AB - Landslides constitute a hazard to life and infrastructure and their risk is mitigated primarily by reducing exposure. This requires information on landslide hazard on a scale that can enable informed decisions. Such information is often unavailable to, or not easily interpreted by, those who might need it most (e.g. householders, local governments and non-governmental organisations). To address this shortcoming, we develop simple rules to minimise exposure to coseismic landslide hazard that are understandable, communicable and memorable, and that require no prior knowledge, skills or equipment to apply. We examine rules based on two common metrics of landslide hazard, (1) local slope and (2) upslope contributing area as a proxy for hillslope location relative to rivers or ridge crests. In addition, we introduce and test two new metrics: the maximum angle to the skyline and the hazard area, defined as the upslope area with slope > 40° from which landslide debris can reach a location without passing over a slope of < 10°. We then test the skill with which each metric can identify landslide hazard - defined as the probability of being hit by a landslide - using inventories of landslides triggered by six earthquakes that occurred between 1993 and 2015. We find that the maximum skyline angle and hazard area provide the most skilful predictions, and these results form the basis for two simple rules: "minimise your maximum angle to the skyline" and "avoid steep (> 10°) channels with many steep (> 40°) areas that are upslope". Because local slope alone is also a skilful predictor of landslide hazard, we can formulate a third rule as "minimise the angle of the slope under your feet, especially on steep hillsides, but not at the expense of increasing skyline angle or hazard area". In contrast, the upslope contributing area has a weaker and more complex relationship to hazard than the other predictors. Our simple rules complement but do not replace detailed site-specific investigation: they can be used for initial estimations of landslide hazard or to guide decision-making in the absence of any other information.
UR - http://www.scopus.com/inward/record.url?scp=85064627224&partnerID=8YFLogxK
U2 - 10.5194/nhess-19-837-2019
DO - 10.5194/nhess-19-837-2019
M3 - Article
AN - SCOPUS:85064627224
SN - 1561-8633
VL - 19
SP - 837
EP - 856
JO - Natural Hazards and Earth System Sciences
JF - Natural Hazards and Earth System Sciences
IS - 4
ER -