Landslide susceptibility mapping based on aerial photograph interpretation inventory for Tegucigalpa, Honduras: An application of the matrix method

Abstract

Tegucigalpa, the capital city of Honduras, is being affected by landslides every year during the rainy season. Although intense rainfall events are likely to be the main trigger of these landslides, anthropogenic disturbances significantly contribute to predispose the populated slopes to failures. Unfortunately, the lack of geotechnical, hydrological and geomorphological data for the study area limits the range of methods available for landslide susceptibility mapping. However, this study summarizes the employment of the matrix method for the development of a landslide susceptibility map; this method was chosen due to its successful application in other data-scarce regions. A landslide inventory based on an aerial photograph interpretation carried out in 2013 by the Japan International Cooperation Agency was used. The study area was divided into cells, and for each cell, the relationship between landslide occurrence and three variables-slope angle, geology and distance to rivers-was determined. For each of the variables, different classes were established. Cells having the same combination of classes were grouped into Unique Condition Units. The Landslide Susceptibility Index, which relates the number of landslide cells to the total number of cells in each Unique Condition Unit, was determined. Based on this index, the landslide susceptibility map was developed and five susceptibility classes were established. Two measures were determined to evaluate the map's performance in depicting landslide-prone areas. On the one hand, the success rate curve shows that the map has an efficiency of 80%. On the other hand, the Degree of Fit reveals that 73% of the landslide cells are successfully classified as having "very high" and "high" susceptibility classes, while 8% of the landslide cells belong to the "low" and "very low" susceptibility classes. Some important observations about the applicability and limitations of this landslide susceptibility map are also provided.