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One of the key ideas of river restoration is that restoring rivers to a more natural status is desirable not only for pure environmental reasons but also to combat flood and geomorphic risk. This paper investigates whether this can be true even in a Mediterranean context, quite different from that of Northern Europe where European river restoration was born. Specifically, we evaluate whether the savings obtained from not implementing new protection works and from maintenance costs not spent – because of elimination of several existing works – exceed the likely increment of flooding and hydromorphological risk. Different conceptual approaches to the decision problem of flood control are synthesised within an integrated, three‐level, evaluation framework. The proposed evaluation framework is applied to a case study on the Chiese River (Po River basin, Italy). Results for this case study are presented. Finally, findings, limitations and potential for application are discussed, concluding that river restoration offers a viable pathway for improving the river environment while not incurring additional economic costs associated with classic flood risk management.

This work aims at integrating the understanding of the river geomorphic dynamic into planning of reservoir operation rules. The case study is a 112 km long reach of the Po river in Italy, from Piacenza to Boretto. The Isola Serafini (IS) gate serves a large run-of-the-river hydroelectricity plant since 1962. The dam blocks a relevant amount of sediments and is cause, together with intense sand mining, for the river bed incision immediately downstream that has made several navigation and irrigation devices unusable during low flow periods, leading to expensive and recurrent works to restore their functionality. The operational rule of IS gate was modelled using 4 parameters and a number of experiments were simulated adopting alternative operating policies over a 10-years period. A 1D hydraulic numerical model with mobile bed has been used to estimate bed degradation trends. The results show that there is space for a meaningful trade-off between the conflicting objectives of hydropower production and reduction of river bed degradation. The analysis provides operative rules able to effectively tackle river bed incision with moderate loss in hydropower production

This paper proposes a tool which river managers may need to ascertain whether the key idea of River Restoration is valid, i.e. that rivers in more natural status are desirable not only for pure environmental reasons, but also to combat flood and geomorphic risk. The point addressed is how to predict the morphology and geometry that a river will assume after the application of a River Restoration project which foresees significant changes in the system of defence and exploitation works as well as morphological adjustments (e.g. reconnection of an incised main channel with the surrounding ex-floodplain). To this aim we developed a semi-quantitative methodology that integrates several differing criteria: from historical analysis of geomorphic evolution, expert-based mechanistic reasoning, checking with empirical qualitative formulas and analytical support from fluvial geomorphology and classic hydraulics. The development of the methodology has taken place on a case study along the 80 km of Chiese River, downstream of Idro lake, in northern Italy. Although the product to be considered is just a pilot one, we see it as a promising tool, which also opens several challenging questions suited for further fascinating research work.