engleski

Object-based Mapping of Gully Erosion in Karstic Area Through the Use of Medium Spatial Resolution Morphometric Parameters

The mapping of gully erosion is important for better understanding of erosion spatial distribution and characteristics, as well as various factors associated with its occurrence. Detailed and accurate gully erosion mapping is especially challenging in remote areas, where high spatial resolution data is not available. Aim of this study was evaluation of potential of different morphometric parameters derived from available medium resolution digital elevation model (DEM) for gully erosion mapping. Mapping was based on object-based image analysis (OBIA) approach and application of multi-resolution segmentation algorithm on seven chosen morphometric parameters (slope, mass balance index, topographic position index, vertical distance to channel network, topographic wetness index, stream power index and planar curvature). This approach was tested on Pag island (284 km²), which is known for its bare karstic landscape and numerous active gullies. Classification was performed on segmented objects based on user-defined thresholds for each used morphometric parameter. As a result, 120 active gully erosion zones were detected and mapped within Pag island. Result validation was performed on 12 randomly chosen locations (10 % of all mapped zones). Extracted gully erosion zones were overlapped with reference data, derived by manual vectorisation from high- resolution orthophoto image. Overlap performance was further quantified through following accuracy indicators: Correctnes (COR), Completeness (COM), Overall Quality (OQ) and LOC measure (LOC). Validation has shown that proposed medium resolution morphometric parameters and object-based approach can be successfully applied for mapping of gully erosion in karstic areas with limited spatial resolution data available. Mapped gully erosion areas were used for determination of general characteristics and spatial distribution of affected areas and correlated with existing gully erosion susceptibility model of Pag island.

OBIA, gully erosion mapping, medium-resolution, morphometric parameters

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