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RESEARCH PRODUCT

Morphological characterization of calanchi (badland) hillslope connectivity

subject

description

Calanchi, a type of Italian badlands created by a combination of water erosion processes and local geomorphological and tectonic controls, is a striking example of long-term landscape evolution. In small temporal/spatial scales, the calanchi exhibit many of the geomorphic processes and landforms that may be observed in fluvial landscapes, hence they may be considered as micro-basins where geomorphic dynamics and landscape features can be related. The goal of this research is testing the use of simple morphometric variables for assessing sediment connectivity of calanchi landforms. In order to detect the morphological characteristics controlling the landscape connectivity of calanchi basins, two areas located in Sicily (Italy) were examined. The investigated features were identified on 119 calanchi basins and mapped using orthophotographs and 2 m resolution DEMs. Application of Hack's law to the calanchi basins showed that the width/length ratio increases with the drainage area, suggesting that calanchi may have a limited connectivity of their hillslopes to the main channel. Moreover the analysis of the drainage network composition suggested that calanchi are sediment removal systems more efficient than river basins. The empirical frequency distribution of the travel time, which is the ratio between the length and the square root of the hillslope steepness, of each cell of the calanchi DEM was established. Finally, for each calanchi basin an index of hillslope connectivity was devised. This was explored as a function of the sediment transport efficiency, itself estimated by the travel time and the corresponding sediment delivery ratio of each calanco hillslope cell.