Regional mapping of carbonate karst landforms and landscape in Central Apennines (Abruzzo, Central Italy)

The Central Apennine is a key sector for karst studies in Italy, nevertheless recent systematic mapping of epigean karst landforms remains scarce. Despite extensive research on hypogene karst and springs, there is a lack of region-wide, high-resolution mapping of surface karst features using modern GIS-based approaches. This study addresses that gap by producing a new comprehensive, multiscale investigation, classification and mapping of karst landforms and landscapes in Central Italy (Abruzzo region)

Carbonate terrains, mainly Jurassic–Cretaceous limestones, cover about 70% of the chain sector of the region and are organized into morpho-structural units bounded by active normal faults. These tectonic features have fragmented ancient karst surfaces and influenced the development of endoreic basins and fluvio-karst drainage patterns. To address this complexity, the research workflow combined traditional geomorphological interpretation with semi-automatic detection techniques applied to multiresolution DTMs (10 m and 5 m), supported by 1 m LiDAR data where available.

The methodology was structured across three scale ranges: (i) small scale (1:200,000–1:50,000) for the definition of carbonate karst morpho-units (CKMUs); (ii) intermediate scale (1:50,000–1:25,000) for the delineation of the main karst areas within CKMUs; and (iii) large scale (1:25,000–1:5,000) for detailed mapping and classification of individual landforms. At the lower scale ranges manual remote mapping was used for larger features, whereas at higher scale, semi-automatic procedures were employed to map smaller features. The applied methods included: (i) fill-sinks algorithms for closed depressions (e.g. dolines, uvala); (ii) raster stacking of DTM-derived parameters (Sky View Factor, Topographic Position Index, curvature) for open depressions; and (iii) supervised filtering of karst valleys from the regional drainage network at 1:5,000 scale.

All outputs were validated through remote checks and field surveys in four representative test areas.

The research workflow led to the definition of:

• 12 CKMUs at regional scale, according to tectonic, morphostructural, and hydrogeological boundaries, which also provided criteria for defining additional sub-units;
• 347 main karst areas at intermediate scale, classified into six types based on landforms clustering: (1) areas with solution dolines; (2) areas with collapse dolines; (3) areas with karst valleys; (4) tectono-karst plains; (5) areas with solution dolines and karst valleys; (6) areas with solution dolines and tectono-karst plains;
• 53,887 landforms mapped at large scale, grouped into five classes: (1) 4,371 closed depressions (closed-contour dolines); (2) 30,247 open depressions (open-contour dolines); (3) 130 karst plains (large uvala, small poljes); (4) 14 poljes; and (5) 19,125 karst valleys (dry or blind valleys). Classification thresholds of depressions were based on surface extension (0.04 km² between dolines and karst plains; 2 km² between karst plains and poljes), with few outliers due to manual adjustments. The resulting dataset was compiled into a regional map (represented at 1:100,000 scale) and stored in a geospatial archive.

This integrated approach demonstrates the effectiveness of combining classic and GIS-based techniques for regional-scale karst feature mapping. The new map and archive provide a replicable framework for further studies and an essential tool for hydrogeological modelling, hazard assessment, and geodiversity management.