577 SESSIONE 17 Key words: Badlands, erosion rate, geomorphological hazard, multitemporal confrontation, Radicofani, reforestations, River Paglia Unit. INTRODUCTION The Radicofani Basin is one of the structural depressions (graben) trending NW - SE of southeastern Tuscany (LIOTTA, 1996), filled with Pliocene marine deposits. The municipality hill area of Radicofani consists mainly of the early Pliocene clayey sediments (River Paglia Unit). Slopes are often covered by colluvial deposits produced by the volcanic neck of Radicofani, consisting of late Pleistocene basalt – trachytic lavas of the Tuscan Magmatic Province. The slopes are widely affected by geomorphological hazard consisting of very frequent badland erosion (CICCACCI et alii, 2008). In this scenario many reforestations were carried out in the last fifty years with the aim at stabilizing slopes on about 320 ha of the municipal territory (Fig.1). Frugal conifers such as Cupressus arizonica, Cupressus sempervirens, Pinus nigra and Mediterranean pines planted in monospecific or mixed stands were mainly used for these forest works. The goal of our study is to evaluate through a multidisciplinary approach the impact of reforestations on the geomorphological instability of nine small drainage basins belonging to the rivers Paglia and Formone watersheds. The geological, geomorphological, hydrological and vegetational characteristics were analyzed by a multitemporal confrontation between the pre – reforestation and post – reforestation situations. The results of our study are a valuable tool to improve both knowledge of the historical morphological dynamics correlated to forest vegetation and land planning and management. METHODOLOGY Each elaboration has been carried out for the year 1954 (pre - reforestation) and year 2007 (post – reforestation). A DEM from historical cartography was constructed and compared with the actual DEM. The difference between the two DEMs leads to estimate the erosion/deposition annual rates for each drainage basin. The aerial – photo interpretation allowed to define areas affected by badland erosion and the results were reported on a GIS to calculate the surface area. The land use was described by the CORINE Land Cover methodology (BOSSARD et alii, 2000) using the ortho - photo interpretation. Furthermore the study of drainage networks on the aerial – photo and GIS environment (Fig. 2) led to calculate the hierarchal anomaly index and the indirect evaluation of denudation rate index (CICCACCI et alii, 1980; DELLA SETA et alii, 2007). Fourteen circular sample plots of ten meters radius were established in the five main forest types to work out the stand such as number of stems, mean diameter, basal area, top height and mean height. The forest survey allowed also to evaluate the adaptability of the tree species used in the reforestations to clayey substrate affected by a high geomorphological hazard setting. Evaluation of reforestation effects through multitemporal investigation in drainage basins affected by badland erosion, Radicofani (Tuscany) FABIO CASTALDI (*), UGO CHIOCCHINI (*) & LUIGI PORTOGHESI (*) Fig. 1 – Reforestation with Cupressus arizonica and Pinus nigra on a slope affected by badland erosion. _________________________ (*) Università della Tuscia, fabio_castaldi@libero.it, chiocchi@unitus.it, lporto@unitus.it