Physical and numerical modelling of a bedload deposition area for an Alpine torrent

Kaitna, Roland; Chiari, Michael; Kerschbaumer, M.; Kapeller, H.; Zlatic-Jugovic, J.; Hengl, Michael; Huebl, Johannes

doi:10.5194/nhess-11-1589-2011

Cited by 22 publications

(10 citation statements)

References 8 publications

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“…Schwindt et al: Sustainable sediment traps can be estimated by the grain size of sediment bars along the channel banks upstream. These bars are silent witnesses of earlier flood events and contain information about sediment transport during past floods (Kaitna and Hübl, 2013). The application of the grain size of the travelling bed load to bed load transport formulae can be used for establishing sediment rating curves, as a computation basis for the dominant discharge.…”

Section: Introductionmentioning

confidence: 99%

Sediment traps with guiding channel and hybrid check dams improve controlled sediment retention

Schwindt

Franca

Reffo³

et al. 2018

Nat. Hazards Earth Syst. Sci.

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Abstract. Sediment traps with partially open check dams are crucial elements for flood protection in alpine regions. The trapping of sediment is necessary when intense sediment transport occurs during floods that may endanger urban areas at downstream river reaches. In turn, the unwanted permanent trapping of sediment during small, non-hazardous floods can result in the ecological and morphological degradation of downstream reaches. This study experimentally analyses a novel concept for permeable sediment traps. For ensuring the sediment transfer up to small floods, a guiding channel implemented in the deposition area of a sediment trap was systematically studied. The bankfull discharge of the guiding channel corresponds to a dominant morphological discharge. At the downstream end of the guiding channel, a permeable barrier (check dam) triggers sediment retention and deposition. The permeable barrier consists of a bar screen for mechanical deposition control, superposed to a flow constriction for the hydraulic control. The barrier obstructs hazardous sediment transport for discharges that are higher than the bankfull discharge of the guiding channel without the risk of unwanted sediment flushing (massive self-cleaning).

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Section: Introductionmentioning

confidence: 99%

Sediment traps with guiding channel and hybrid check dams improve controlled sediment retention

Schwindt

Franca

Reffo³

et al. 2018

Nat. Hazards Earth Syst. Sci.

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“…However, morphodynamic modelling of gravel migration has so far been more common in perennial braided gravel bed rivers (e.g. Williams et al, 2016b) or laboratory flumes (Kaitna et al, 2011) than in ephemeral rivers. There are examples of simulating sediment transfer in ephemeral channels (Graf, 1996), although most of the few recent simulations have been performed in sandy reaches (Billi, 2011;Lucía et al, 2013) and on alluvial fans (Pelletier et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Topographical change caused by moderate and small floods in a gravel bed ephemeral river – a depth-averaged morphodynamic simulation approach

et al. 2018

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Abstract. In ephemeral rivers, channel morphology represents a snapshot at the end of a succession of geomorphic changes caused by floods. In most cases, the channel shape and bedform migration during different phases of a flood hydrograph cannot be identified from field evidence. This paper analyses the timing of riverbed erosion and deposition of a gravel bed ephemeral river channel (Rambla de la Viuda, Spain) during consecutive and moderate-(March 2013) and low-magnitude (May 2013) discharge events, by applying a morphodynamic model (Delft3D) calibrated with pre-and post-event surveys by RTK-GPS points and mobile laser scanning. The study reach is mainly depositional and all bedload sediment supplied from adjacent upstream areas is trapped in the study segment forming gravel lobes. Therefore, estimates of total bedload sediment mass balance can be obtained from pre-and post-field survey for each flood event. The spatially varying grain size data and transport equations were the most important factors for model calibration, in addition to flow discharge. The channel acted as a braided channel during the lower flows of the two discharge events, but when bars were submerged in the high discharges of May 2013, the high fluid forces followed a meandering river planform. The model results showed that erosion and deposition were in total greater during the long-lasting receding phase than during the rising phase of the flood hydrographs. In the case of the moderate-magnitude discharge event, deposition and erosion peaks were predicted to occur at the beginning of the hydrograph, whereas deposition dominated throughout the event. Conversely, the low-magnitude discharge event only experienced the peak of channel changes after the discharge peak. Thus, both type of discharge events highlight the importance of receding phase for this type of gravel bed ephemeral river channel.

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“…• The duration of the falling limb t ̱ (in s) is 1.7 times as long as the rising limb t ̟ (in s), which is typical for floods of mountain rivers (Armanini and Larcher, 2001;D'Agostino and Lenzi, 1996;Kaitna et al, 2011;Piton and Recking, 2016a;Rickenmann et al, 1998); 30 Nat. Hazards Earth Syst.…”

Section: Experimental Procedures 25mentioning

confidence: 99%

Experimental study of sediment traps permeable for frequent floods

Schwindt

Franca

Reffo

et al. 2017

Preprint

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Abstract. Sediment traps created by partially open torrential barriers are crucial elements for flood protection in alpine regions. 10The trapping of sediment is necessary when intense sediment transport occurs during floods that may endanger urban areas at downstream river reaches. In turn, the unwanted permanent trapping of sediment during small, non-hazardous floods can result in the ecological and morphological depletion of downstream reaches. This study experimentally analyses a new concept for permeable sediment traps. For ensuring the sediment transfer up to small floods, a guiding channel implemented in the deposition area of the sediment trap was studied systematically. The bankfull discharge of the guiding channel corresponds to 15 a dominant morphological discharge. At the downstream end of the guiding channel, a permeable barrier triggers sediment retention and deposition. The permeable barrier consists of a bar screen for mechanical deposition control, superposed to a flow constriction for the hydraulic control. The fail-safe clogging of the barrier and the sediment deposition upstream can be ensured for discharges that are higher than the bankfull discharge of the guiding channel.

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Physical and numerical modelling of a bedload deposition area for an Alpine torrent

Cited by 22 publications

References 8 publications

Sediment traps with guiding channel and hybrid check dams improve controlled sediment retention

Sediment traps with guiding channel and hybrid check dams improve controlled sediment retention

Topographical change caused by moderate and small floods in a gravel bed ephemeral river – a depth-averaged morphodynamic simulation approach

Experimental study of sediment traps permeable for frequent floods

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