Relationships between a new slope morphometric index and calanchi erosion in northern Sicily, Italy Marcello Buccolini a, ⁎,LauraCoco a , Chiara Cappadonia b , Edoardo Rotigliano b a Dipartimento di Geotecnologie per l'Ambiente ed il Territorio, Università “G. d'Annunzio” Chieti-Pescara, Via dei Vestini 30, 66013 Chieti Scalo (CH), Italy b Dipartimento di Scienze della Terra e del Mare, Università degli Studi di Palermo, Via Archirafi 20, 90123 Palermo, Italy abstract article info Article history: Received 13 August 2011 Received in revised form 24 December 2011 Accepted 17 January 2012 Available online 24 January 2012 Keywords: Slope morphometry Badlands processes Drainage network The Italian badlands, or “calanchi”, are common landforms in Mediterranean areas including central and southern Italy. Calanchi landforms may be compared to small hydrographic basins. These landforms are characterised by dense, hierarchical and rapidly evolving drainage systems carved into steep clayey slopes and by a sharply alternating pattern of furrows and narrow, generally sharp crests. This work presents a study of morphometric characteristics and a statistical analysis for two sites in northern Sicily(Italy),onoutcropsofsilty-claydepositsaffectedbyactiveerosionprocesses,whichgivethisareaatypical calanchi landscape. In particular, factors closely linked to the characteristics of the hydrographic network and slope morphometry were considered and analysed. The initial geometry of the slopes was reconstructed and statisticallycomparedwiththatofthecurrent calanchi slopesincludingthedrainagenetwork. Anewmorphometricindex(MorphometricSlopeIndex, MSI)wasdefinedtorepresenttheinitialslopegeome- tryasawhole.Thisindexwasfoundtobeeffectiveindefiningthestructureofhydrographicnetworks,summar- ising the characteristics and type of slope evolution, and quantifying the rate of soil erosion. The rate was determined based on both linear (gully erosion) and areal (landslides, sheet and rill erosion) morphogenetic processes, and our analysis based on MSI indicates the dominance of areal erosion. MSI couldalsobeusedfor basinslargerthan calanchi torepresentthecharacteristicsofgeomorphicprocesses. © 2012 Elsevier B.V. All rights reserved. 1. Introduction cThebadlandsinItalyaretypicallycharacterisedbytwotypesofland- form: “biancane” and “calanchi”. Biancane (plural of biancana) are small clay domes that are found in groups, with the sides crossed by micro- rills and micro-pipes, and they are often covered by vegetation and sur- rounded by micro-pediment (Torri and Bryan, 1997; Farifteh and Soeters, 2006). Among the forms of accelerated erosion characterising the clay landscapes of Italy, calanchi (plural of calanco) are perhaps the most spectacular. Calanchi widely occur in hilly and mountain areas in and around the Apennines of central and southern Italy, namely Emilia, Marche, Abruzzo, Puglia, Basilicata, Tuscany, Lazio, Calabria and Sicily. Calanchi canbedefinedasverydense,hierarchisedandrapidlyevolving drainage systems carved into steep clayey slopes, characterised by a sharply alternating pattern of furrows and very narrow and generally sharp crests with a height between a few and several tens of metres (Castiglioni, 1933; Vittorini, 1977; Alexander, 1980; Dramis et al., 1982; Clarke and Rendell, 2000; Moretti and Rodolfi, 2000). The genesis of theselandformsiscontrolledbythemechanicalandchemical/mineralog- ical characteristics of the lithotypes involved, their particle size composition and the structural setting of the geological substratum (Vittorini, 1977; Rodolfi and Frascati, 1979; Bryan and Campbell, 1986; de Lugt and Campbell, 1992; Torri and Bryan, 1997; Regüés et al., 2000; FariftehandSoeters,2006;DellaSetaetal.,2007).Thepresenceofsteep vegetation-freeclayslopesisaprerequisiteforthedevelopmentof calan- chi (Castiglioni,1933;Guasparri,1978;Dramisetal.,1982).Also,climatic conditionsinfluencethemorphogenesisofthe calanchi;itisfavouredby strong seasonal contrasts typical of the Mediterranean climate (Csa of Köppen,1936).Theseasonalcontrastsarerelatedtothedeepdesiccation ofsoilsinsummerandintensehydrationcyclesinwinter. The evolution of the drainage network can produce calanchi land- forms, which may be compared to a small drainage basin or hydro- graphic unit. Erosion processes in calanchi include both linear erosion (gully erosion, rill erosion and piping) and areal erosion (slide or flow-type landslips and sheet erosion) (de Lugt and Campbell, 1992; Torri and Bryan, 1997; Moretti and Rodolfi, 2000). Linear erosion requiresasufficientlysteepslope,thelackofwhichmayleadtoreticu- larpipingandtheemergenceof biancane. The research described in this paper started from the assumption thatthemorphometriccharacteristicsoftheslopesignificantlyaffect the calanchi dynamics. There have been limited morphometric stud- ies concerning the slope characteristics of calanchi, and they refer mainly to slope steepness (Castiglioni, 1933; Sfalanga and Rizzo, 1974; Rodolfi and Frascati, 1979). Other studies mainly analysed the Geomorphology 149-150 (2012) 41–48 ⁎ Corresponding author. Tel.: +39 0871 3556424; fax: +39 0871 3556146. E-mail address: buccolini@unich.it (M. Buccolini). 0169-555X/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.geomorph.2012.01.012 Contents lists available at SciVerse ScienceDirect Geomorphology journal homepage: www.elsevier.com/locate/geomorph