Abstract:
The article presents the results of GIS-based terrain analysis for identification and extraction of relevant landforms and landform elements in Archaro-Orsoyska lowland (Northwestern Bulgaria). The methodology used includes calculation of local (e.g. slope and aspect) and compound geomorphometric variables (e.g. vertical distance to channel network, distance to channel network, topographic wetness index, and others), as well as landform elements such as valleys, depressions, slope elements, ridges, and summits. Spatial analysis methods such as zonal statistics, overlay functions, and visualization of obtained results, were used for identification of the landforms in the investigated area. To outline the landform elements was used the concept of geomophons (geomorphologic phonotypes) (Neteler, Mitasova, 2007; Jasiewicz, Stepinski, 2013; Stepinski, Jasiewicz, 2011) giving lookup distance L (in meters) and flatness threshold t (in degrees) to allow extractions of landforms and their elements with different sizes. Based on the methodological approach used in this study, the following main landforms in the Archaro-Orsoyska lowland were identified: natural loess leveés, flat and negative relief forms in floodplains, abandoned channels, sand bars, artificial dikes and embankments, remnants of river terraces, landslides, hilly loess accumulative surfaces, undulated through rills and dray valleys. The obtained results were compared with previous geomorphologic studies and satellite images, and will be used for a reconnaissance survey and geomorphologic mapping in order to create a geomorphological classification of genetic types of deposits and landforms in the study area.