What river morphology after restoration? The methodology VALURI

Abstract

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.

Process‐based assessment of success and failure in a constructed riffle‐pool river restoration project

“…This gap is perpetuated by a lack of effective post-construction monitoring of instream restoration projects (Bernhardt et al, 2007;Miller & Kochel, 2009;Morandi et al, 2014;Poppe et al, 2016). Assessment of restoration project performance is often done through hydraulic simulations and predictive models (Khosronejad et al, 2013(Khosronejad et al, , 2014Krapesch et al, 2009;MacWilliams et al, 2006;Nardini & Pavan, 2012;Rhoads et al, 2008).…”

River restoration: not only for the sake of nature but also for saving money while addressing flood risk. A decision‐making framework applied to the Chiese River (Po basin, Italy)

“…There are also technical limitations: Hydraulic prediction (the quasi‐2D simulation model adopted) can be certainly improved specifically to determine flooded areas (see Koivumäki et al ., for a thorough discussion of this type of uncertainty). The prediction of the future river geomorphology corresponding to each ALTernative (not discussed in this paper, see Nardini and Pavan, ) is a challenging task definitely affected by high uncertainty. Vulnerability is certainly quite rough and should be refined. …”

“…a coordinated set of actions within each action line aiming at achieving the desired objectives, inspired to Approach d: ‘multi‐objective (QoL)’ ; definition of ALTernatives : each one specifies a possible course of actions within the same strategy; prediction of effects for each ALTernative : in particular, this has to deal with the geomorphic evolution of the river, i.e. predicting the new morphology corresponding to the new future dynamic equilibrium – this is presented in Nardini and Pavan () – and corresponding eroded and flooded areas under a specified Scenario , for several recurrence times T R (in the case study: 2, 5, 10, 20, 50, 200, 500 years); integrated comparative evaluation of the ALTernatives as close as possible to the three‐stage framework presented earlier through calculation of relevant evaluation indices and due sensitivity analysis; negotiation and choice ; specification with implementation plan . …”

“…Longitudinal works are represented by their cumulative length in kilometres, while punctual works are represented by their total number. The corresponding morphological evolution is not presented here for reasons of space (see Nardini and Pavan, 2012 time TR and the water storage of upstream water reservoirs before the flood comes, which determines flood peak reduction. Other important Scenario variables -not considered in our case study -include urbanisation patterns (e.g.…”

A Qualitative Hydro-Geomorphic Prediction of the Destiny of the Mojana Region (Magdalena-Cauca Basin, Colombia), to Inform Large Scale Decision Making

“…(viii) Mapping of sediment sources should cover the whole region and models estimating supply-based on empirical formulas like for instance the RUSLE [45]-should be calibrated by performing historical sediment budgets of relevant reaches and reservoirs, which would take into account morphological changes and all inputs/losses. (ix) A "story of the river" for relevant, representative river reaches would be elaborated which would describe synthetically and systematically the changes experienced so far, capturing amongst others those changes that are due to damming (the idea is introduced in [46], a very nice example is provided by [47]). (x) The historical mobility space of the rivers should be determined as a reference [48].…”