Application of historical cadastral maps and high resolution airborne LiDAR topography to distinguish anthropogenic from natural karst landforms: case study of karst dolines

Dolines are concave circular karst landforms that are clearly presented by topography data (topographic maps), especially on high-resolution LiDAR digital terrain models (DTM). In the karst landscape, man has reshaped natural dolines through centuries by collecting rocks and soil to increase the flat area of tillable (cultivated) land at the bottom of the doline. By this human-induced process, the natural doline was reshaped into a cultivated doline. Cultivated dolines have a rich historical legacy of use for local agricultural production, high geomorphological value for geodiversity and present an important habitat supporting biodiversity. They are an element of agro-karstic landscape (paysage agro-karstiques) and are distinctive of Mediterranean karst landscapes like Dinaric karst, Central massive, Apulia etc. Most of the cultivated dolines have been recently abandoned, and covered by forest, thus the human impact is not evident anymore so clearly.

In most studies on natural characteristics and processes in dolines, there is no distinct separation between natural and cultivated dolines and no consideration of past agricultural land use. Thus, the main goal of this study/presentation is to provide a geoinformatics methodology to separate cultivated dolines from natural dolines based on differences in micro-topography by using recent very high-resolution LiDAR topography data and historical cadastral maps (19^th century).

Using visualized LiDAR DTM the most evident morphometric differences between the natural and cultivated doline landforms were recognized. Cultivated dolines were characterized by (1) a circular concave landform with a flat bottom (2) the presence of anthropogenic elements, such as circular stonewalls at the upper doline edge, which provides evidence of stone-removal from the doline slopes (smooth surface). Additionally, in the 19th-century cadastral maps, only individual dolines with important land use were marked as special lots. Given the rural character of the landscape during that time, the only land use recorded in the concentric lots of the dolines was agricultural use (arable fields, gardens, meadows, and pastures). As a result, the number, location and surface coverage of cultivated dolines were precisely defined for classical karst regions in SW Slovenia. Based on Lidar data, bowl-shaped cultivated dolines with flat bottoms were separated from non-cultivated funnel-shaped dolines.