Assessment and Quantitative Evaluation of Loess Area Geomorphodiversity Using Multiresolution DTMs (Roztocze Region, SE Poland)

Abstract

The geodiversity of loess areas is reflected in the characteristic dataset of loess landforms, with the dominance of several types of valley forms (mainly gullies). The availability of satellite elevation data and high-resolution aerial topography scanning data provides an opportunity for quantitative assessment of geomorphodiversity. This is done through the analysis of topographic texture, delimitation and statistical characterization of the topographic parameters of erosional landforms, such as volume and degree of dissection (density of valleys) or the degree of ‘coverage’ of the area by valley forms. An important factor affecting the accuracy of the estimation is the accuracy of the underlying digital terrain model (DTM). This study compares three digital terrain models, with cell sizes of 30, 10 and 1 m, generated from satellite altimetry data and airborne laser scanning (ALS) data. The subregion of Szczebrzeszyn Roztocze (Western Roztocze Region, SE Poland), i.e., one of the most typical loess relief regions in Poland, was selected as the study area. Selected topographic texture analyses were carried out using the SLRM (Simple Local Relief Model) algorithm. Delimitation of valleys was performed by delineating the extent of slope change in two key steps: (1) detection of areas below the average topographic surface; (2) delimitation using supervised classification of DTMs. The results of the study show that the accuracy of delimitation of valleys increases inversely proportional to the DTMs resolution. Automated topographic texture analysis allows delimitation and extraction, as well as statistical analysis of parameters of valleys. Finally, two indicators have been proposed, Relative Valley Area (RVA) and Area-normalised Valley Cubature (AVC), which can be used in geomorphodiversity studies of a geologically homogeneous area. The dimensionless RVA index can also be expressed as a percentage (%) of the area of valley forms in a basic field of 1 km2. Furthermore, the AVC index shows the dynamic character of the main relief features of the analysed area.

Keywords

• geomorphodiversity of loess areas
• loess relief
• gullies
• multiresolution DTMs
• automatic landforms detection