1928 F. S. Segura et al. Copyright © 2007 John Wiley & Sons, Ltd. Earth Surf. Process. Landforms 32, 1928–1946 (2007) DOI: 10.1002/esp Earth Surface Processes and Landforms Earth Surf. Process. Landforms 32, 1928–1946 (2007) Published online 11 April 2007 in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/esp.1506 Morphometric indices as indicators of tectonic, fluvial and karst processes in calcareous drainage basins, South Menorca Island, Spain Francesca S. Segura, 1 * Josep E. Pardo-Pascual, 2 Vicenç M. Rosselló, 1 Joan J. Fornós 3 and Bernadí Gelabert 3 1 Department of Geography, Universitat de València, València, Spain 2 Department of Cartographic Engineering, Geodesy and Photogrammetry, Universitat Politècnica de València, València, Spain 3 Department of Earth Sciences, Universitat de les Illes Balears, Palma de Mallorca, Balearic Islands, Spain Abstract This study proposes using morphometric indices to discriminate the processes that shape calcareous drainage basins. To illustrate this, a DEM of the southern part of Menorca Island (Migjorn) was created and basin slope, drainage density, hypsometric curve and integral, and the area occupied by open and closed dolines were extracted from it. These indices show an important dependence on tectonics, which govern the morphology of these drainage basins and encourage the predominance of karst and/or fluvial processes in the different sectors. The morphometric indices are clearly influenced by the geological Migjorn struc- ture, a carbonate Upper Miocene reef platform gently folded as an asymmetrical anticline. The hypsometric integral and curve discriminate the influence of tectonics and structure whilst the drainage density and the proportion of open dolines are associated with basins with more pronounced fluvial processes. A cluster analysis based on these indices discrimi- nated three sectors where different forms and processes are found. In the western and eastern sectors, rounded basins without major fractures predominate. The basins slope at less than 5°, and karst processes outweigh fluvial processes. The central sector, however, has steeper slopes, a clearly defined drainage system, and a predominance of fluvial over karst processes. Greater uplift in this sector has facilitated the formation of elongated basins that follow the main fracture lines. Copyright © 2007 John Wiley & Sons, Ltd. Keywords: morphometric indices; drainage basin processes; tectonics; geomorphometry; DEM *Correspondence to: Dr. Francesca S. Segura, Department of Geography, Universitat de València, Avenida Blasco Ibáñez 28, 46010 València, Spain. E-mail: Francisca.Segura@uv.es Received 6 July 2006; Revised 10 January 2007; Accepted 29 January 2007 Introduction The processes involved in landscape evolution can be difficult to detect and quantify. Since drainage basins are shaped by tectonic and erosional processes, the purpose of this study is to demonstrate the potential use of morphometric parameters extracted from DEMs to determine the relative importance of these processes. The study area is the south of Menorca Island, a carbonate Upper Miocene reef platform (Migjorn), which shows varied geomorphological evolution despite lithologic and climatic homogeneity. The lithologic and climatic uniformity of the Migjorn area allows exclusion of these variables, facilitating the interpretation of the role other factors have had in shaping the river basins. Geomorphological photointerpretation (Rosselló, 2004), field work (Rosselló et al., 2004) and the morphometric analysis of the entire area (Pardo and Porres, 2004), as well as sediment analyses of quaternary deposits of the ravines (Fornós and Segura, 2004) and wetlands (Segura et al., 1999; Pardo, 2003), have shown that there is an irregular distribution of the tectonic, karst and fluvial processes in the study area. Until recently it has been difficult to establish chronological and causal relationships between these processes, as well as their relative degrees of significance for the different drainage basins.