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 structure, 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 discriminated 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.In our recent research (Gelabert et al., 2005) we found that the higher elevation of the carbonate platform is a fundamental element for the configuration of the Migjorn relief, as deduced from the orientation of the fractures and the distribution of the fluvial network. To confirm this, we performed a geomorphological characterization based on basin measurements that were statistically tested. The purpose was to objectively assess the importance of tectonics, karst and fluvial activity, as well as their interdependence. Consequently, a series of morphometric indices (slope, drainage density, hypsometric integral and curve, and percentage of closed and open dolines) were analysed to explain the irregular distribution of fluvial, karst and tectonic processes detected in the study area. The first three morphometric indices were used to explain the formation of the drainage network and the degree of basin evolution; the latter two were introduced to characterize the karst. The presence of tectonics can be deduced from most of the indices used.Drainage density reflects the factors governing dissection of the basins. Numerous studies relate this index to climate, vegetation (Gregory and Gardiner, 1975;Schumm, 1997) and lithology (Schumm, 1997;Tucker et al., 2001). More interesting for our work are the studies that show that drainage density is sensitive to slope. Some studies suggest drainage density is higher on steep slopes with a predominance of overland flow (Dietrich et al., 1992(Dietrich et al., , 1993Montgomery and Dietrich, 1994). Other authors, however, have found a ...
