Susceptibility factors of drainage basins to shallow landslides in coffee-growing areas in the Department of Caldas, Colombia

Due to its geo-environmental complexity and its climatic conditions, the coffee-growing region of the Department of Caldas, Colombia is affected by shallow landslides triggered by rainfall. With the objective of characterizing the factors affecting the susceptibility to mass movements in regional drainage basins and to contribute to an understanding of the susceptibility of landslides in coffee-growing regions, the present study was conducted in the Mica Basin of the Municipality of Pacora, Colombia, at 5°32′28.14′′ N, 75°29′15.35′′ W. With the support of the GIS platform, the inventory of landslides was carried out using orthophotographs and Light Detection and Ranging (LiDAR) information from 2014 at a 10 m × 10 m resolution. This inventory was complemented with field surveys that included susceptibility factors and the influence of the roads. The predisposing factors to landslides were studied using frequency ratio (FR) analysis and multiple logistic regression (MLR) analysis. The FR analysis showed a close relationship among landslides (FR index > 1) with a slope between 27° and 65°, an altitude between 2100 m and 2420 m, a distance to natural drainages between 0 and 40 m, a distance to geological faults between 0 and 200 m, a distance to roads between 20 and 400 m, basic and ultrabasic geological units, soil compounds derived from volcanic ash, and plane curvatures of concave and convex types. The MLR model showed a maximum likelihood ratio of certain factors, such as geology, relief forms, slope angle, altitude, flow direction, plane curvature, distance to natural drainage, distance to faults, and distance to roads, with the probability of landslide occurrence.