Magnitude-frequency characteristics and preparatory factors for spatial debris-slide distribution in the northern Faroe Islands

Mads-Peter Jakob Dahl, Niels H. Jensen, Anita Veihe, Lis Mortensen

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The Faroe Islands in the North Atlantic Ocean are highly susceptible to debris-avalanches and debris-flows originating from debris-slide activity in shallow colluvial soils. To provide data for hazard and risk assessment of debris-avalanches and debris-flows, this study aims at quantifying the magnitude and frequency of their debris-slide origins as well as identifying which preparatory factors are responsible for the spatial debris-slide distribution in the landscape. For that purpose a debris-slide inventory was generated from aerial photo interpretation (API), fieldwork and anecdotal sources, covering a 159 km(2) study area in the northern Faroe Islands. A magnitude-cumulative frequency (MCF) curve was derived to predict magnitude dependant debris-slide frequencies, while preparatory factors responsible for spatial debris-slide distribution were quantified through GIS-supported discriminant function analysis (DFA). Nine factors containing geological (lithology, dip), geomorphological (slope angle, altitude, aspect; plan and profile curvature) and land use (infield/outfield, sheep density) information were included in the multivariate analysis. Debris-slides larger than 100 m(2) with magnitude expressed as topographic scar area can be predicted from the power-law function: Y = 936.26X(-1277), r(2) = 0.98 while a physical explanation is preferred for the roll-over pattern of smaller slope failures. The DFA is able to correctly classify app. 70% of the modeled terrain units into their pre-determined stable/unstable groups. Preparatory factors responsible for the spatial debris-slide distribution are aspect, slope angle, sheep density, plan curvature and altitude, while influence of the remaining factors is negligible. (C) 2012 Elsevier B.V. All rights reserved.
Sider (fra-til)3-11
StatusUdgivet - 2013


  • Debris-slides
  • Flow-type landslides
  • The Faroe Islands
  • Aerial photograph interpretation
  • Magnitude-frequency analysis
  • Discriminant function analysis

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