Evaluating landslide susceptibility using environmental factors, fuzzy membership functions and GIS

A methodology for landslide susceptibility assessment to delineate landslide prone areas is
presented using factor analysis and fuzzy membership functions and Geographic Information
Systems (GIS). A landslide inventory of 51 landslides was created in the mountainous part of Xanthi
prefecture (North Greece) and the associated conditioning factors were determined for each
landslide by field work. Six conditioning factors were evaluated: slope angle, slope aspect, land use,
geology, distance to faults and topographical elevation. Fuzzy membership functions were defined
for each factor using the landslide frequency data. Factor analysis provided weights (i.e., importance
for landslide occurrences) for each one of the above conditioning factors, indicating the most
important factors as geology and slope angle. An overlay and index method was adopted to produce
the landslide susceptibility map. In this map 96% of the observed landslides are located in very high
and high susceptibility zones, indicating a suitable approach for landslide susceptibility mapping.