River Morphodynamic Evolution Under Dam-Induced Backwater: An Example from the Po River (Italy)

Abstract

The Isola Serafini dam interrupts the Po River continuity creating a backwater zone that modifies river hydrodynamics for up to 30 km upstream. Lateral migration rates of meanders reduce downstream, and coarse-grained channel-bars are progressively drowned and reworked over time. The size of river bed sediment decreases downstream across the backwater zone. The size of river bedforms increases downstream across the backwater zone. Dam-induced backwater forced an up-flow shift of the gravel-sand transition.

Ephemeral rollover points and clinothem evolution in the modern Po Delta based on repeated bathymetric surveys

“…Following the end of the Little Ice Age, a growth rate of 47 m/year is reported for the Po di Pila lobe, after 1886 AD (Correggiari, Cattaneo, & Trincardi, 2005a;Correggiari et al, 2005b), when the anthropic E-W straightening of the main branch of the Po River was carried out to protect the delta plain from flooding (Visentini & Borghi, 1938). After 1945, the entire Po Delta, including Po di Pila, underwent a generalised phase of degradation and partial retreat, primarily reflecting a decrease of sediment supply caused by dam construction (Maselli et al, 2018;Maselli & Trincardi, 2013), rapid subsidence of up to 1.5 cm/year (Teatini, Tosi, & Strozzi, 2011), and riverbed mining activities and channelization of watercourses (Stefani & Vincenzi, 2005). The most significant retreat phase, with rates in the order of tens of metres per year, reached its peak between 1954 and 1978.…”

Two Dimensional Model for Backwater Geomorphology: Darby Creek, PA

“…Approximately 7 rkm of the lower part of the creek is estimated to be in BW conditions. Water 2019, 11,2204 3 of 20 mainly limited to either a few years-worth or thousands years of geomorphic changes [29][30][31][32][33][34][35][36][37][38]. In contrast, the presented integrated model builds on the existing body of knowledge in geosciences which can predict geomorphological alterations in the BW zone of the rivers over a short to intermediate time scale applicable to civil engineering applications.…”

“…Water 2019, 11,2204 12 of 20 analysis between the dates does not discriminate between erosion and deposition (Figure 7a), the higher the reflectance, the more likely there will be increased land surface disturbance (erosion or deposition of the sediment) resulting from a flood event [68]. The output of the integrated model can predict and discriminate where erosion and deposition will occur (Figure 7b).…”

“…In addition to coastal areas, dammed rivers are also subjected to backwater (BW) conditions. Dams act as blocks on rivers and by forming backwater conditions, change the water surface profile upstream [7][8][9][10][11]. By 2018, there were more than 59,000 large dams built all around the world [8].…”

“…The vertical velocity distribution in BW conditions is less divergent compared to the one in a uniform flow [14]. These changes in the hydraulics of the vertical and horizontal flow velocity in BW zones consequently alter the sediment transport processes.Current approaches to BW in morphological studies are primarily based on either measured or estimated hydraulic parameters coupled with the estimated sediment transport [9,11,[15][16][17][18][19][20][21]. The studies of sediment transport in BW conditions are scarce due to the complex dynamics of the sediment transport in BW zones and the lack of field-measured data.…”