Using geomorphometric approach to investigate spatial pattern and intensity of erosional dissection in a block-faulted topography (Orlickie-Bystrzyckie Mountains, Central Europe)

Abstract

The paper presents an attempt to recognize areas of enhanced erosional dissection, based on a combined analysis of several geomorphometric variables and using four different approaches (rank-based, cold and hot spot analysis, k-means clustering of ‘raw’ data, and k-means clustering of local measures of spatial autocorrelation). The study area includes the Orlickie-Bystrzyckie Mountains Block (OBMB), which is a block-faulted range within the Sudetes Mountains, Central Europe, typified by fault-generated range fronts, remnant planation surfaces and topographic ramps due to large-scale tilting. Geology is diverse, with basement rocks and sedimentary cover, and the relevant timescale is late Cenozoic. Morphometric variables derived from a LiDAR-based DEM include contour length, standard deviation of elevation, median valley depth and standard deviation of curvature, and are considered to account for various morphometric signatures of erosional dissection. While deriving compound measures of dissection, three grid cell sizes were considered. Within the OBMB several areas were identified as erosionally dissected to a considerable degree. Their spatial pattern is complex and reflects several factors simultaneously. Differential uplift appears as the main trigger, but the erosional response varies, depending mainly on the size of runoff contributing area – itself related to the pattern of uplift, and the distance from the margins of elevated areas. Lithology (bedrock resistance to erosion) seems to play a subordinate role. We also discuss various issues related to the procedures themselves, pointing out their advantages and limitations. Procedural setups proposed in this paper are not site-specific and may be used in various topographic and geological settings.