ASSESSMENT OF LAND COVER CHANGES ON FLOOD GENERATION IN A TYPICAL VITICULTURAL LANDSCAPE: THE VERNAZZA CATCHMENT, CINQUE TERRE NATIONAL PARK, LIGURIA, ITALY

Mediterranean catchments and in particular terraced landscapes are sensitive to temperature oscillations, rainfall intensity and human activities; all of these factors imply significant environmental problems in terms of soil erosion and control of the meteoric waters. The aim of this research is to assess the hydro-geomorphological effects of different land cover scenarios in Vernazza catchment (Cinque Terre National Park, Italy). It shows typical characteristics present in most of the Ligurian coastal terraced catchments: small catchment area, very steep slopes and particular land-use pattern. The slopes have been almost completely terraced for vineyards during the past millennium. Due to socio-economic changes, the traditional cultivations have been progressively abandoned over the last decades. Subsequently, Mediterranean scrub and pine vegetation succession replaced the former cultivated areas. The climate is Mediterranean, with hot and dry summers and mild winters. In particular, on October, 25th 2011 a heavy rainfall affected the area, with a cumulative daily rainfall of 539 mm recorded. This event triggered several slope movements and floods, causing 13 death casualties, as well as severe structural and economic damages. To evaluate the hydrological and geomorphological consequences of different land cover, we applied a simple Soil Conservation Service Curve Number (SCS-CN) method (SCS, 1956) which was implemented in a GIS. To assess the SCS-CN model scenario, four different land use scenarios under the recent flood were simulated:1) The landscape under present conditions; 2) The re-cultivation of all abandoned terraced vineyards; 3) The landscape covered by garrigue and pine (recent abandoned terraces); 4) The landscape completely covered with Mediterranean scrub and woods (long time abandoned terraces). From this preliminary study it seems that the recultivation of all abandoned terraces is not a good strategy to contrast runoff, while our model results enhance that forests with an excellent leaf cover reduce rainfall impact to soil and so runoff. The applied methodology represent an valuable tool for the preparation of plans and strategies of land use /risk management in the Cinque Terre National Park.