Favorability values of geological,vegetation and relief factorsfor the development of soil creep landforms

摘要

Soil creep can produce small landforms on slope surfaces, such as lobes, terraces or steps, stripes and superficial irregularities or hummock topographies. The aim of the present study was to analyze the relationship between the cartographic distribution of these small landforms and some geological, geomorphologic, vegetation and relief variables. A total of 1,324 landforms produced by soil creep were mapped within a study area of 250 km2, located in an Atlantic mountainous zone in the north of the Iberian Peninsula. The variables considered in the analysis were: 1) geological-geomorphologic variables: bedrock geology, surficial formations (lithologic and genetic classification), vegetation and presence of rock area, and 2) relief variables: elevation, slope, aspect, curvature, relief index, flow accumulation and Compound Topographic Index (CTI). The influence of each variable in the development of the creep landforms was studied by favorability analysis. The results obtained show that presence of creep landforms is more frequent in slopes with calcareous lithologies and surficial deposits, and in those slopes with higher values of elevation, slope angles of approximately 25-35, high curvature value and relief index higher than 5 an lower than 9. Nevertheless, some relief variables, such as CTI or flow accumulation (which describes water movement and accumulation over the surface of the slope), do not appear to have a strong influence on the distribution of creep landforms.