Monitoring and numerical modelling of riverbank erosion processes: a case study along the Cecina River (central Italy)

Abstract

Riverbank retreat along a bend of the Cecina River, Tuscany (central Italy) was monitored across a near annual cycle (autumn 2003 to summer 2004) with the aim of better understanding the factors influencing bank changes and processes at a seasonal scale. Seven flow events occurred during the period of investigation, with the largest having an estimated return period of about 1·5 years. Bank simulations were performed by linking hydrodynamic, fluvial erosion, groundwater flow and bank stability models, for the seven flow events, which are representative of the typical range of hydrographs that normally occur during an annual cycle. The simulations allowed identification of (i) the time of onset and cessation of mass failure and fluvial erosion episodes, (ii) the contributions to total bank retreat made by specific fluvial erosion and mass-wasting processes, and (iii) the causes of retreat. The results show that the occurrence of bank erosion processes (fluvial erosion, slide failure, cantilever failure) and their relative dominance differ significantly for each event, depending on seasonal hydrological conditions and initial bank geometry. Due to the specific planimetric configuration of the study bend, which steers the core of high velocity fluid away from the bank at higher flow discharges, fluvial erosion tends to occur during particular phases of the hydrograph. As a result fluvial erosion is ineffective at higher peak discharges, and depends more on the duration of more moderate discharges. Slide failures appear to be closely related to the magnitude of peak river stages, typically occurring in close proximity to the peak phase (preferentially during the falling limb, but in some cases even before the peak), while cantilever failures more typically occur in the late phase of the flow hydrograph, when they may be induced by the cumulative effects of any fluvial erosion.

Response of lateral channel dynamics of a lowland meanderingriver to engineering-derived adjustments - an example of theMorava River (Czech Republic)

“…Our nding stays in agreement with the works of many authors [e.g. [61][62][63][64] that emphasized the importance of local and/or temporal speci cs on pattern of river bank erosion.…”

Numerical simulation of hydrodynamics and bank erosion in a river bend

“…A detailed description of these activities, together with a discussion of the overall results, is reported by Luppi et al [2008]. For the purposes of this paper we focus on the first monitoring period, between October and December 2003.…”

Channel migration inferred from aerial photographs, its timing and environmental consequences as responses to floods: A case study of the meandering Topľa River, Slovak Carpathians

“…It leads to an increased rate of erosion/deposition processes in the channel (Hooke, 1979;Miller, 1990;Hrádek, 2000;Richard et al, 2005;Larsen et al, 2006;Kiss et al, 2008;Pišút, 2008). Bank erosion processes depend on the size of the discharge and the interactions between the ever-changing hydrological conditions (the flow velocity, local hydraulics, floods and their magnitude, frequency, duration and timing) and other factors contributing to bank erodibility (initial bank geometry, planform geometry, height and density of vegetation, volume of accessible sediments, sediment grain size) (Knighton, 1998;Russell et al, 2004;Luppi et al, 2009), as well as floodplain land cover and overall riverine landscape management.…”