Modelling the effect of time‐dependent river dune evolution on bed roughness and stage

Paarlberg, Andries; Dohmen-Janssen, Catarine M.; Hulscher, Suzanne J.M.H.; Termes, A.P.P.; Schielen, Ralph Mathias Johannes

doi:10.1002/esp.2074

Cited by 61 publications

(83 citation statements)

References 38 publications

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“…Although their formation and geometry of inclined co-sets is at least partially dependent on the erosive nature of the separated flow in the lee of the downslope-migrating bedforms, the behavior of (interacting) separated flow patterns (Fernandez et al 2006) within a larger-scale non-uniform flow is not known. Moreover, bedform superimposition is both caused and affected by flow unsteadiness (Allen and Collinson 1974;Allen and Friend 1976;Allen 1982;Ten Brinke et al 1999;Kleinhans 2002;Leclair 2002;Paarlberg et al 2006;Paarlberg et al 2007;2009;Paarlberg et al 2010). Inclined sets do provide useful information on the sedimentary dynamics despite these gaps in our understanding.…”

Section: Foresets: Inclined Co-setsmentioning

confidence: 99%

Evidence of Bedform Superimposition and Flow Unsteadiness In Unit-Bar Deposits, South Saskatchewan River, Canada

Reesink¹,

Bridge²

2011

Journal of Sedimentary Research

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Unit-bar deposits are ubiquitous components of river-channel deposits and strongly influence their hydrological properties, yet they are not easy to interpret. This paper concerns details of the internal structures of six unit bars from the South Saskatchewan River, Canada, that were investigated using trenches, epoxy resin peels, and 900 MHz ground-penetrating radar (GPR) profiles. The composition of unit bars depends on flow unsteadiness and superimposed bedforms. Flow unsteadiness causes changes in the mean grain size of the sediment in transport, but is expressed primarily as a change in the type and direction of migration of smaller ripple-and dune-scale bedforms superimposed on unit bars. Superimposed bedforms with heights that exceed 25% of the host bedform height reduce their host's slope and generate inclined sets. Host bedforms with smaller superimposed bedforms form angle-of-repose cross strata with a visible pre-sorting pattern. The relationship between the formative host-and superimposed bedforms and such pre-sorted cross strata can be used to interpret numerous aspects of the three-dimensional geometries of the bedforms. Such detailed interpretations rely on: (i) regularly spaced finegrained drapes deposited during the passage of troughs of superimposed bedforms, (ii) grain-size sorting patterns generated by sorting within the superimposed bedforms before deposition, (iii) grain-size sorting during deposition by grainfall and intermittent grainflows down the bar lee-slope, and (iv) the presence and nature of low-angle reactivation surfaces.The detailed interpretations revealed that the deposits of dam-related floods were significantly smaller than the deposits of individual unit bars in this study. The unsteady flow and sediment transport conditions are reflected by changes in the structural composition of the unit bars. Reactivation surfaces associated with flow unsteadiness, as opposed to those formed by large superimposed bedforms, were characterized by changes in mean grain size, the buildup of sediment at the base of the bar lee slope, and changes in structures formed by superimposed bedforms. Reactivation surfaces generated by large superimposed bedforms indicate that bedform preservation is likely increased in areas of flow deceleration. The trough deposits of exposed unit bars contained bubble sand, planar laminae due to upper-stage plane beds, and low-angle inclined laminae due to antidunes. These structures indicate that unit-bar troughs can act as ephemeral channels. The composition of the investigated unit bars thus emphasizes the interplay between flow unsteadiness and bed morphology in the formation of sedimentary structures in river channels.Sediment surfaces generate visible GPR reflections where the thickness and contrast in electrical properties of the sediment layers are sufficiently large. Most cross-stratified sets were represented only by reflections from the base of the set, and not by high-angle inclined reflections from the cross strata. The local absence of refle...

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Section: Foresets: Inclined Co-setsmentioning

confidence: 99%

Evidence of Bedform Superimposition and Flow Unsteadiness In Unit-Bar Deposits, South Saskatchewan River, Canada

Reesink¹,

Bridge²

2011

Journal of Sedimentary Research

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“…These temporal variations in k s through a tidal cycle may, in practice, be unrealistically large, particularly for dunes, due to the present lack of any bed form history effects in our simulations. From observations made in time-varying river flows Paarlberg et al [2010] have pointed out that observed dune heights do vary significantly in time, exhibiting a hysteresis lag with regard to the flow strength, and Coleman et al [2010] have proposed a predictive scheme for k s in such circumstances. However, intratidal variation in k s may actually be relatively small due to the time scales required for dunes to evolve.…”

Section: Internal Coupling and Methods Of Feedbackmentioning

confidence: 99%

A large scale morphodynamic process-based model of the Gironde estuary

Villaret¹,

Huybrechts²,

Davies³

2012

NCK-days 2012: Crossing Borders in Coastal Research: Jubilee Conference Proceedings NCK-days 2012

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We present here our effort to develop a morphodynamic model of the Gironde estuary, using a process-based approach. In this complex and strongly dynamical environment, internal coupling between the flow (Telemac-2d) and sediment transport models (Sisyphe) allows the representation of detailed sediment processes and interactions with the bed, using a bed roughness feedback method. In this complex and highly heterogeneous environment, the sediment bed composition had to be schematized assuming 3 classes of bed material. Model results could be further improved by accounting for the cohesive sediment (consolidation processes). Thanks to parallelization of the codes, the simulation takes only 18 hrs on 8 processors (linux station) to calculate the 5-year bed evolution, at the basin scale (150 km).

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“…This means that dune formation influences the stage-discharge relationship and this should be included in hydrodynamic models. River dunes are found in nearly all river systems with the river bed consisting of sand, small gravel or mixtures (Julien et al, 2002;Paarlberg et al, 2007Paarlberg et al, , 2010Wilbers and Ten Brinke, 2003).…”

Section: Data Analysis and Model Developmentmentioning

confidence: 99%

Water resource assessment along the Blue Nile River, north Africa with a one-dimensional model

Ali¹,

Crosato²,

Mohamed³

et al. 2014

Proceedings of the Institution of Civil Engineers - Water Manag

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The water resource of the Blue Nile River in north Africa is under increasing pressure due to rapid population growth and economic development. The situation is aggravated by a lack of coordinated management and governance, partly caused by incomplete knowledge of the water supplies, uses and needs. Proper water management is particularly important now, considering the recently completed and planned mega dams on the Blue Nile River network. This paper reports on the construction of a one-dimensional hydrodynamic model covering the entire Blue Nile River system, from Lake Tana to the confluence with the White Nile, with the aim of quantifying water availability throughout the year, for different conditions. The work included an extensive field measurement campaign along the Blue River and its tributaries, both in Ethiopia and Sudan. Calibrated and validated with independent datasets, the model was used to quantify water uses in the period 2008-2010, which were then compared with the official figures. The results show that the dry season is characterised by extra water losses that should be taken into account when quantifying water needs, especially during the filling up phase of new reservoirs.

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Modelling the effect of time‐dependent river dune evolution on bed roughness and stage

Cited by 61 publications

References 38 publications

Evidence of Bedform Superimposition and Flow Unsteadiness In Unit-Bar Deposits, South Saskatchewan River, Canada

Evidence of Bedform Superimposition and Flow Unsteadiness In Unit-Bar Deposits, South Saskatchewan River, Canada

A large scale morphodynamic process-based model of the Gironde estuary

Water resource assessment along the Blue Nile River, north Africa with a one-dimensional model

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