Terraced Landscapes and Hydrogeological Risk. Effects of Land Abandonment in Cinque Terre (Italy) during Severe Rainfall Events

Abstract

During 25 October 2011, an extremely intense rainfall event occurred in Eastern Liguria and Northern Tuscany. Severe damages were registered in the Monterosso and Vernazza basins, located in the famous area of Cinque Terre, which have been affected by hundreds of landslides, mud flows, and erosions. The main feature of the Cinque Terre landscape is the presence of terraced cultivations on steep slopes facing the sea. The area represents a remarkable cultural landscape, is a National Park, and is included in the World Heritage List of the UNESCO. This work aims to analyze the effect of abandoned terraced land on hydrogeological risks and in landslide prevention, by comparing what happened in Cinque Terre to other experiences presented in scientific literature. The cessation of maintenance of dry stone terraces due to the crisis of traditional agriculture was identified as the main cause of failure during the heavy rainfall event. However, we found some contrasting and, in some cases, unexpected results in the literature regarding the effects of the vegetation that develops on abandoned terraces. This paper compares different results in order to better understand what the future of terraced landscapes is and which are the best management strategies for such complex and fragile territories. In particular, where they represent a cultural heritage and a resource for the rural economy.

Terraced Landscapes on Portofino Promontory (Italy): Identification, Geo-Hydrological Hazard and Management

“…The largely abandoned terraces in the studied areas represent a possible cause of hazard [12,20,34,37]: erosion and collapse of terraces may be an additional source area for debris, general instability and shallow landslides. Recently, many events of collapse involved terraced areas in the region in a similar context, due to high rain intensity phenomena: in 5 Terre (close to La Spezia- Figure 2A) in 2011, more than 300 small debris caused a total amount of approximately 100,000 m 3 in a 5.4 km 2 catchment [13,32,33] and in 2014 in Leivi, approximately 12 km east from the studied area (close to Chiavari- Figure 2A), debris moved from a terraced area, causing two casualties [40]. Another shallow landslide event happened in late November 2019, impacting a highway pier and causing its collapse close to Savona, in the wester Riviera at approximately 60 km west from the studied area.…”

“…This superficial alteration modified the water cycle at terrace, slope and landscape scale. In many steep slope-or soildegraded agricultural areas, terracing practice and maintenance may represent a contribution to decrease the geo-hydrological hazard: soil erosion, shallow landslides, debris flow and flash floods effects may result mitigated [10,[20][21][22][32][33][34][35]. Particularly, flash flood effects may decrease both at the local scale and at the basin one, with the risk mitigation for the exposed elements that are in the lower part of basins: population, buildings and infrastructures.…”

“…Particularly, flash flood effects may decrease both at the local scale and at the basin one, with the risk mitigation for the exposed elements that are in the lower part of basins: population, buildings and infrastructures. The lack of stone walls maintenance may cause an increase of geo-hydrological risk: their possible collapse may represent a source area for debris/hyper-concentrated flow with a possible high damaging power [32,33,[35][36][37]. A similar lack of maintenance of older, pre-1950s surface and subsurface drainage structures is recognized in localities with increasing landslide hazard [38].…”

Evaluación de los servicios ecosistémicos proporcionados por las terrazas agrícolas

“…Cyprus Galletti et al, 2013Spain Arévalo et al, 2017Arnáez et al, 2015;Asins 2006Asins , 2009García Ruíz et al, 2013;Lasanta, 1990Lasanta, , 2014Lasanta et al, 2001Lasanta et al, , 2013Ramos & Martínez-Casanovas, 2006;Reynes Trias, 2006;Romero Díaz et al, 2007Romero Martin et al, 2016. Greece Koulouri & Giourga, 2007;Price & Nixon, 2005 Italy Agnoletti et al, 2019;Bazzoffi et al, 2006;Brandolini et al, 2017;Paliaga et al, 2016;Tarolli et al, 2014Portugal Pacheco et al, 2014Czech Republic Dumbrovsky et al, 2014Kovár et al, 2016;Kosulic et al, 2014Russia Borisov et al, 2012Slovenia Ažman et al, 2016Kladnik et al, 2016 evaluating the environmental and socioeconomic impacts and the cost-benefit ratio of the implementation and maintenance of agricultural terraces; (ii) determining the ES provided in different countries and climates; and (iii) contrasting these results with the data from the scientific literature concerning the impacts of terraces on ES.…”

Geomorphological Landscape Research and Flood Management in a Heavily Modified Tyrrhenian Catchment

“…The research focuses on important landscape features such as terraces and built up surfaces, and on the urbanisation and modification of the riverbed. Terraces are particularly important as deep modifications of natural geomorphological dynamics artificially inducing a reduction of slope gradient and solid transport, [16][17][18]. It is argued that sustainable landscape management policies for marginal and rural areas aimed at the reduction of flood hazard and vulnerability have to combine a qualitative and quantitative approach.…”