How natural are Alpine mountain rivers? Evidence from the Italian Alps Francesco Comiti* Faculty of Science and Technology, Free University of Bozen-Bolzano, Bolzano, Italy Received 27 April 2011; Revised 8 November 2011; Accepted 8 November 2011 *Correspondence to: Francesco Comiti, Faculty of Science and Technology, Free University of Bozen-Bolzano, piazza Università 5, 39100 Bolzano, Italy. E-mail: francesco. comiti@unibz.it ABSTRACT: Historical, human-induced channel adjustments in lowland gravel-bed rivers have been documented in several geographical contexts worldwide. In particular, it is now widely accepted that the vast majority of European rivers are far from any natural, reference state prior to anthropic disturbances, and a ‘complete’ restoration is hardly achievable. However, few inves- tigations have addressed changes that have occurred in mountain rivers of the Alps, and these channels are commonly reckoned quite ‘natural’ by society. This paper intends to describe how human pressure on Italian Alpine basins has been quite relevant for several centuries – in terms of land-use variations, in-channel structures, timber transport (splash damming) and riparian vegetation management – such that nowadays ‘reference conditions’ cannot be found even in small mountain creeks. In addition, recent natural climatic variations (e.g. the Little Ice Age) are superimposed on human disturbances, thus defying the definition of any ‘equilibrium’ morphological conditions even under ‘human-free’ states. A summary of published as well as unpublished works on historical channel adjustments in rivers of the Italian Alps is presented in order to document the impacts deriving from human pressure at different basin scales and for different river morphologies, from steep confined streams to large unconfined rivers. General options for river management and restoration actions aiming to combine geomorphological functionality and flood hazard mitigation are discussed, in the light of the current European legislative context. Copyright © 2011 John Wiley & Sons, Ltd. KEYWORDS: environmental history; hydromorphology; river restoration; Water Framework Directive Introduction European society looks at mountain creeks and rivers of the Alps as paradigmatic of quasi-natural ecosystems. In Italy such view is probably even more rooted in the population as a result of the very dense urbanization of its limited lowland territory, whereas the upper mountain valleys of the Alps and of the Appennines may appear as areas of limited anthropic altera- tions. The perception of mountain streams is thus of greater naturalness compared to lowland rivers because the latter feature widespread embankment and straightening, flow through cultivated and urban lands, and are generally characterized by a reduced water quality due to agricultural, industrial and urban wastes. Indeed, water quality (i.e. pollution) is still the main charac- teristic of rivers cared of by the average ‘man of the street’ as well as by most public administrators, where water quality and river quality are interchangeable categories. Water quality of mountain streams is actually mostly good throughout the Alps, apart from short reaches downstream of the largest towns and of occasional industrial areas (Alpine Convention, 2009). Furthermore, fish are relatively abundant in most mountain rivers, even though their populations are the result of heavy fish- ery management. As a consequence, Alpine mountain rivers are perceived neither as human-modified nor at risk by the popula- tion, similarly to other regions of the world (Wohl, 2001). However, the ‘Water Framework Directive’ (2000/60/EC, hereafter WFD) issued by the European Union is forcing river managers and thus society to change attitude towards river quality. In fact, WFD requires European States to assess the ecological integrity of their internal water bodies with respect to ‘natural reference conditions’ (European Commission, 2000). The ecological quality of a water body is established as the combination of physiochemical, hydromorphological (where ‘hydromorphology’ is defined by WFD as ‘the physical characteristics of the shape, the boundaries and the content of a water body’, a term less commonly used in the scientific community than ‘hydrogeomorphology’, which will be uti- lized in the paper hereafter) and biotic characteristics, and is classified into five classes. Member states are obliged to take to ‘good’ status (the second quality class below the highest one) before 2015 all natural water bodies featuring lower status by means of restoration actions, apart from the case of ‘highly modified water bodies’ (HMWB). Therefore, a sound understanding of the hydrogeomorphological quality and ‘naturalness’ of river channels is needed for the application of WFD. Indeed, the much wider scope of hydrogeomorphol- ogy in the evaluation of river ecology and in guiding river restoration is widely accepted (see e.g. Newson and Large, 2006; Bertoldi et al., 2009; Vaughan et al., 2009) and should be borne in mind by river managers, beyond the mere appli- cation of WFD. EARTH SURFACE PROCESSES AND LANDFORMS Earth Surf. Process. Landforms (2011) Copyright © 2011 John Wiley & Sons, Ltd. Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/esp.2267