Hydro‐sedimentological processes in meandering rivers

Blanckaert, Koen

doi:10.1002/9781119424437.ch12

Cited by 5 publications

(2 citation statements)

References 114 publications

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“…Hydrodynamic modelling can provide meaningful scenarios for water resources management and allow the assessment of interactions between hydromorphological processes and landforms (Blanckaert, 2018; Mosselman, 2005). Increasing the modelling accuracy and capacity over larger areas promotes the knowledge of ongoing dynamics, which is particularly important for the prediction of events with extreme magnitude, i.e., flash floods.…”

Section: Introductionmentioning

confidence: 99%

Enhancement of two‐dimensional hydrodynamic modelling based on UAV‐ flow velocity data

Wolff,

Lotsari,

Spieler

et al. 2024

Earth Surf Processes Landf

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Abstract2D hydrodynamic models deepen the understanding of hydromorphological processes in fluvial systems. UAV (Unoccupied Aerial Vehicles) can record complementary calibration and validation data for these models of large areas. In this study, we created a 2D hydrodynamic model of the Pulmanki River in Northern Finland under shallow, open‐channel conditions based on three calibration sets. We examined the potential of UAV‐flow velocities for model validation. Here, we applied a cross‐validation approach comprising the conversion from surface to depth‐averaged velocity and vice versa using fixed velocity coefficients (α). We further assessed the conversion performance including hydraulic variables to evaluate this coupled numerical‐experimental concept. Our model showed good performance in the three calibration runs for water level and depth‐averaged velocity. The calculation of surface to depth‐averaged velocity identified the coefficient α = 0.8 as the best choice with R2 = 0.62 for the straight river reach, indicating a good agreement between converted velocity and the reference data. A poor agreement, however, is evident for the meander section with R2 = 0.406. While there were no statistically significant relationships between the conversion performance and hydraulic variables, there were observable trends in the residuals indicating over‐ and underestimation of converted velocities, particularly in relation to bathymetry and distance to the channel centre, with variations based on the river structure. Our study demonstrates that UAV reference data has the potential to enhance 2D hydrodynamic models but particularly improves our understanding of spatial flow distribution.

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Section: Introductionmentioning

confidence: 99%

Enhancement of two‐dimensional hydrodynamic modelling based on UAV‐ flow velocity data

Wolff,

Lotsari,

Spieler

et al. 2024

Earth Surf Processes Landf

View full text Add to dashboard Cite

show abstract

“…Point‐bar deposits are formed by lateral stacking of inclined beds (Bridge et al ., 1995; Moody & Meade, 2014), which can vary in grain size from mud to gravel (Bridge et al ., 1995; Kostic & Aigner, 2007; Simon & Gibling, 2017). Sediment is transported along the bend in a three‐dimensional flow configuration, which is characterized by a secondary helical circulation developed downstream of the bend apex (Hooke, 1975; Ferguson et al ., 2003; Blanckaert, 2019). This secondary circulation moves sediment from the thalweg zone towards the inner bank, allowing the bar to accrete laterally.…”

Section: Introductionmentioning

confidence: 99%

Reconstruction of an extreme flood hydrograph and morphodynamics of a meander bend in a high‐peak discharge variability river (Powder River, USA)

Ghinassi

Moody

2021

Sedimentology

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Understanding of morphodynamic processes associated with large-scale floods has recently improved following significant advances of modern technologies. Nevertheless, a clear link between flood discharge and in-channel sedimentation processes remains to be resolved. The hydrological and geomorphological data available for the meandering Powder River (Montana, USA) since 1977 makes it a perfect laboratory to investigate connections between flood discharge and point-bar sedimentation processes. This study focuses on a pointbar that accreted laterally ca 70 m during a 50-year recurrence flood, which lasted about 14 days in May 1978. In September 2018, a trench ca 2 m deep and 70 m long was excavated through the axial point-bar deposits, and the 1978 flood deposits were delineated based on georeferenced pre-flood and post-flood cross-section surveys. Sedimentological data show that point-bar deposits accumulated at the early and late flood stages, when the flow was confined to the channel, and have similarities with classical facies models in terms of palaeocurrent patterns and vertical grain-size trend. However, during high-stage flood conditions, when the flow overtopped the bar, cross-cutting of the bar and armouring were typical processes. Integration of sedimentological and palaeo-hydrological data highlight that the relation between channel cross-sectional area and flood discharge play a key role in preserving bar deposits. The integrated approach adopted here provides a basis for advancing palaeoflood hydrology beyond the stage of estimating peak discharges to the next stage of estimating palaeoflood hydrographs.

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Distinguishing mid‐channel and bank‐attached fluvial bars by flow divergence: Implications for the interpretation of stratigraphic records

et al. 2021

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The characterization of ancient fluvial-channel bars informs predictions of sedimentary facies distribution, and hence they are critical for interpreting river morphodynamics through time. Within active fluvial channels, sediment storage occurs along the banks or along their axial portion, generating bank-attached or mid-channel bars, respectively. This study introduces the angle of flow divergence (Δf), measured as the angle between the azimuths of bar accretionary slopes and local dune migration, and quantitatively explores its distribution in 103 channel reaches that have a sandy bed load and clear water. This dataset includes both mid-channel and bank-attached bars from low-variable peak discharge rivers of Russia and Brazil. Remotely sensed evidence shows that dune migration transverse to the dip azimuth of bar slopes (Δf ≅ 90-110°) occurs both in mid-channel and bank-attached bars, contradicting the long-standing tenet that palaeoflows nearly orthogonal to the dip azimuth of large-scale inclined strata are indicative of sinuous, single-thread palaeochannels. Only Δf values significantly higher (>140°) or lower (<60°) than 90°discriminate mid-channel and bank-attached fluvial bars. Comparisons between Δf values and bar-accretionary styles suggest that mid-channel bars formed by high-peak and low-peak variable discharge rivers tend to preserve axially and laterally accreting deposits, respectively. Nearly orthogonal divergence angles are found in bank-attached bars irrespective of peak-discharge variability. While stressing that analyses akin to the one presented here are to be complemented with additional sedimentological information from high-quality outcrops, this study proposes a new, quantitative, approach to better distinguish fluvial bars, and hence possibly the planform pattern of associated channel bodies, from sedimentary successions. In particular, the data show that a reliable distinction between mid-channel and bank-attached bars should be based on comprehensive palaeocurrent and architectural information from various portions of preserved bar bodies, and that inferences based on limited datasets should be considered with caution.

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Hydro‐sedimentological processes in meandering rivers

Cited by 5 publications

References 114 publications

Enhancement of two‐dimensional hydrodynamic modelling based on UAV‐ flow velocity data

Enhancement of two‐dimensional hydrodynamic modelling based on UAV‐ flow velocity data

Reconstruction of an extreme flood hydrograph and morphodynamics of a meander bend in a high‐peak discharge variability river (Powder River, USA)

Distinguishing mid‐channel and bank‐attached fluvial bars by flow divergence: Implications for the interpretation of stratigraphic records

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