Hurricane event-based method to create regional hazard maps for heavy rainfall-induced translational landslides

Abstract

This paper proposes a hurricane event-based method to construct a map for heavy rainfall-induced translational landslides. This method involves five steps: (1) construct a GIS-based geotechnical database; (2) identify the areas in the vicinity which are susceptible to translational landslides based on the slope of the terrain and the geological information available; (3) characterize the heavy rainfall hazard due to hurricanes (typhoon) as a set of collectively exhaustive and mutually exclusive stochastic events, that fully describe spatial distribution and annual frequency of occurrence (in accordance with storm category, storm position, distance between the eye of the storm and the site of interest, among others factors); (4) compute the ratio between the steady-state rainfall produced by a hurricane event affecting the tributary area of the slope under analysis, Qs, and the critical steady-state rainfall necessary to trigger slope instability, Qc, and finally; (5) carry out a probabilistic translational landslide hazard analysis to estimate the exceedance rate of a given ratio Qs/Qc. This method is applied to maps of Mexico for return periods of 50 and 150 years. The results shown in these maps are estimates of where the translational landslides may occur, and they should be useful to carry out local studies and to elaborate recommendations of site-specific hazard reduction plans as well as to calculate insurance rates. In addition to this, these results are useful for identifying actions of civil protection, regional and local risk management, and land use planning, as well as the promotion of more detailed vulnerability and risk studies on different scales.