Comparing landslide inventory maps Mirco Galli, Francesca Ardizzone, Mauro Cardinali, Fausto Guzzetti ⁎ , Paola Reichenbach CNR-IRPI, via della Madonna Alta 126, 06128 Perugia, Italy Received 15 July 2005; received in revised form 25 February 2006; accepted 9 September 2006 Available online 14 June 2007 Abstract Landslide inventory maps are effective and easily understandable products for both experts, such as geomorphologists, and for non experts, including decision-makers, planners, and civil defense managers. Landslide inventories are essential to understand the evolution of landscapes, and to ascertain landslide susceptibility and hazard. Despite landslide maps being compiled every year in the word at different scales, limited efforts are made to critically compare landslide maps prepared using different techniques or by different investigators. Based on the experience gained in 20 years of landslide mapping in Italy, and on the limited literature on landslide inventory assessment, we propose a general framework for the quantitative comparison of landslide inventory maps. To test the proposed framework we exploit three inventory maps. The first map is a reconnaissance landslide inventory prepared for the Umbria region, in central Italy. The second map is a detailed geomorphological landslide map, also prepared for the Umbria region. The third map is a multi-temporal landslide inventory compiled for the Collazzone area, in central Umbria. Results of the experiment allow for establishing how well the individual inventories describe the location, type and abundance of landslides, to what extent the landslide maps can be used to determine the frequency-area statistics of the slope failures, and the significance of the inventory maps as predictors of landslide susceptibility. We further use the results obtained in the Collazzone area to estimate the quality and completeness of the two regional landslide inventory maps, and to outline general advantages and limitations of the techniques used to complete the inventories. © 2007 Elsevier B.V. All rights reserved. Keywords: Landslide map; Inventory; Density; Susceptibility; Map comparison; Umbria 1. Introduction Landslides play an important role in the evolution of landforms (Harmon and Doe, 2001), and represent a serious hazard in many areas of the World (Brabb and Harrod, 1989). Several investigators have attempted to identify landslides and to produce landslide maps. Depending on the purpose and the available resources, landslide inventory maps are compiled at different scales, from the local to the national, using a variety of techniques, including the analysis of stereoscopic aerial photographs, geomorphological field mapping, engi- neering-geological slope investigations, and the exam- ination of historical archives (Guzzetti et al., 2000). A combination of these techniques is often used. Landslide inventory maps are prepared for different purposes, including: (i) showing the location and type of landslides in a region (Antonini et al., 1993; Cardinali et al., 2001; Antonini et al., 2002a), (ii) showing the Available online at www.sciencedirect.com Geomorphology 94 (2008) 268 – 289 www.elsevier.com/locate/geomorph ⁎ Corresponding author. Tel.: +39 075 5014421; fax: +39 075 5014420. E-mail address: Mirco.Galli@irpi.cnr.it (M. Galli). 0169-555X/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.geomorph.2006.09.023