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

Abstract

Research Article| October 16, 2018 River Morphodynamic Evolution Under Dam-Induced Backwater: An Example from the Po River (Italy) Vittorio Maselli; Vittorio Maselli 1University of Aberdeen, School of Geosciences, Aberdeen, U.K. 2Institute of Marine Sciences, ISMAR-CNR, Bologna, Italy Search for other works by this author on: GSW Google Scholar Claudio Pellegrini; Claudio Pellegrini 2Institute of Marine Sciences, ISMAR-CNR, Bologna, Italy Search for other works by this author on: GSW Google Scholar Fabrizio Del Bianco; Fabrizio Del Bianco 3Consorzio ProAmbiente, Bologna, Italy Search for other works by this author on: GSW Google Scholar Alessandra Mercorella; Alessandra Mercorella 2Institute of Marine Sciences, ISMAR-CNR, Bologna, Italy Search for other works by this author on: GSW Google Scholar Michael Nones; Michael Nones 4Research Centre for Constructions, Fluid Dynamics Unit, University of Bologna, Bologna, Italy Search for other works by this author on: GSW Google Scholar Luca Crose; Luca Crose 5Agenzia Interregionale per il Fiume Po, AIPO, Settore Navigazione Interna, Parma, Italy Search for other works by this author on: GSW Google Scholar Massimo Guerrero; Massimo Guerrero 6Department of Civil, Chemical, Environmental and Material Engineering, University of Bologna, Bologna, Italy Search for other works by this author on: GSW Google Scholar Jeffrey A. Nittrouer Jeffrey A. Nittrouer 7Rice University, Department of Earth, Environmental, and Planetary Sciences, MS-126, Houston, Texas 77005, U.S.A. Search for other works by this author on: GSW Google Scholar Journal of Sedimentary Research (2018) 88 (10): 1190–1204. https://doi.org/10.2110/jsr.2018.61 Article history first online: 16 Oct 2018 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Tools Icon Tools Get Permissions Search Site Citation Vittorio Maselli, Claudio Pellegrini, Fabrizio Del Bianco, Alessandra Mercorella, Michael Nones, Luca Crose, Massimo Guerrero, Jeffrey A. Nittrouer; River Morphodynamic Evolution Under Dam-Induced Backwater: An Example from the Po River (Italy). Journal of Sedimentary Research 2018;; 88 (10): 1190–1204. doi: https://doi.org/10.2110/jsr.2018.61 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentBy SocietyJournal of Sedimentary Research Search Advanced Search Abstract River systems evolve in response to the construction of dams and artificial reservoirs, offering the possibility to investigate the short-term effects of base level oscillations on fluvial architecture. A major effort has been dedicated to the understanding of river response downstream of large dams, where deep channel incisions occur in response to the removal of sediment that is sequestered in the upstream reservoir. Integrating field observations and numerical-modeling results, this work quantifies the sedimentary and morphological changes of the Po River (Italy) upstream of the Isola Serafini dam to investigate the impact of dam-induced backwater on river morphodynamics. The construction of a reservoir generates a new base level that forces an upstream shift of alluvial lithofacies and a change in the planform geometry of the river. The lateral migration rate of the channel is up to 45 m/yr upstream of the influence of backwater flow and ca. 10 m/yr at the transition from normal to backwater flow conditions (30 km from the dam). Within this reach, a reduction of the bed shear stress promotes deposition of coarse-grained sediment and the emergence of the gravel–sand transition of the river. The lateral migration of the channel continuously decreases over time, and rates < 5 m/yr can be observed in the reservoir backwater zone. This trend is accompanied by the drowning of channel bars, the reduction of river competence, and an increase in bedform spacing. Oscillatory backwater and drawdown surface water profiles can be observed closer to the dam, which are associated with varying low-discharge and high-discharge events, respectively. While low-flow conditions, persisting for much of the year, allow the deposition of fine-grained sediment, high-discharge events promote not only the resuspension and transport of fine material but also the progressive erosion of channel bars and the overall deepening of the thalweg. This study provides a clear picture of the river evolution in response to the construction of a hydropower dam that may be of help in predicting how other fluvial systems will respond to future human interventions. Moreover, the result of how changes in base level and oscillations in water surface profile (backwater and drawdown) control river hydro-morphodynamics and sediment transport may provide new insights when reconstructing ancient fluvial and deltaic sequences. You do not currently have access to this article.