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This paper focuses on the temporal elements of the REFORM hydromorphological framework, illustrating these elements with an analysis of information from the lower Tagliamento river, Italy. It presents an analysis of historical channel adjustments at segment and reach scales over the last two centuries, reflecting human pressures that are summarised but not fully developed in this paper, and an analysis of data from aerial photographs, topographic surveys, and river flow records. This is followed by an assessment of likely future changes over the period 2012-2035 based upon both a conceptual model founded on the historical analysis and numerical modelling. The Tagliamento river has gone through three main phases of adjustment. The first two phases, characterized by narrowing and incision, were driven primarily by human interventions (i.e. sediment mining and channelization). The most recent phase represents an attempt of the river to achieve a new equilibrium condition and is mainly controlled by flow regime (i.e. frequency and magnitude of formative discharges) and vegetation establishment. As for future channel evolution, both models showed that slight width changes are likely to occur over the period 2012-2035. Channel widening, that could be expected as a response to an excess of unit stream power, will be hampered by vegetation establishment. Finally, the 'no intervention' strategy seems to be the best option for leading the river towards a new equilibrium condition and to achieve different goals (e.g. flood mitigation, conservation or improvement of ecological status). [ABSTRACT FROM AUTHOR]

Abstract: Interpretation of channel changes is not always straightforward since it requires a detailed reconstruction of the evolutionary trajectory of channel morphology, a quantitative analysis of controlling factors and, finally, identification of links between evolutionary trajectories and controlling factors. The aim of this paper is to explain channel adjustments and controlling factors in the Tagliamento River, a large gravel-bed river in northeastern Italy. Traditional methods for studying historical channel changes (i.e., use of aerial photos, topographic data) were employed, but numerical modelling turned out to be very useful for the quantification of bedload transport and for supporting interpretation of past changes and likely future channel evolution. River channel underwent three main phases of adjustment over the last 200years. The first two phases, from the end of the nineteenth century to the early 1990s, were characterized by narrowing (channel width decreased from 1250 to 540m) and incision (about 1m); and the third phase, from the 1990s to present day, by widening (from 540 to 600m) and slight aggradation (about 0.2m). Combining evolutionary trajectories of channel morphology and analysis of controlling factors we argue that the long-term channel evolution of the Tagliamento River was driven mainly by human intervention at the reach scale (i.e., sediment mining and channelization). Changes in sediment supply in the catchment area had no, or minor, effects in the study reach. The most recent changes (i.e., widening and slight aggradation) are explained as a response to past disturbances that have produced a remarkable change of channel geometry and an increase of unit stream power in the reach. Magnitude and frequency of formative discharges are a key driving factor of the intensity of recent changes, while this was not the case during the previous phases of adjustment. [Copyright &y& Elsevier]