The influence of environmental and lithologic factors on rockfall at a regional scale: an evaluation using GIS

Analysis of the spatial distribution of rockfall deposits at a regional scale (over an area of 250 km2 of northern Spain) using a cartographic database supported by a Geographic Information System (GIS) reveals several relationships between rockfall activity and environmental variables. Recent rockfall activity is inferred when recent scree is preserved at the bottom of the rock slopes. In order to identify the slope source areas of the scree we have mapped the depositʹs drainage basin, applying topographic criteria, and we have combined these basins with the rock slopes map. A method for setting the basin boundaries automatically will replace manual cartography. This method is based on algorithms available within many commercial software programs and originally planned to analyse the behaviour of fluids over a topographic surface. sults obtained by combining the rockfall area source map with the geology and DTM show the relationships between the distribution of rockfall deposits and lithology, elevation and slope of the rockwall and a strong control of the joint type and density. Elevation influence on rockfall has been associated with climatic variations with elevation. Other variables, such as orientation, show complex influences that are difficult to interpret.