Computational Models of Flow, Sediment Transport and Morphodynamics in Rivers

Escauriaza, Cristián; Paola, Chris; Voller, V. R.

doi:10.1002/9781118971437.ch1

Cited by 7 publications

(6 citation statements)

References 107 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The application of hydro-morphodynamic physically based numerical models (generally known as computational-fluiddynamic models -CFDs) over the last 20 years has mainly been focused on idealized channel configurations at the laboratory scale (Wu et al, 2000;Defina, 2003;Rüther and Olsen, 2005;Abad et al, 2008) or the morphological dynamics of natural channels over short time periods (Darby et al, 2002;Chen and Duan, 2008;Li et al, 2008;Wang et al, 2008;Zhou et al, 2009). The limited range of application of these models reflects unresolved issues of data availability and high computational demands (Escauriaza et al, 2017).…”

Section: The Caesar-lisflood Modelmentioning

confidence: 99%

Assessment of the geomorphic effectiveness of controlled floods in a braided river using a reduced-complexity numerical model

Ziliani

Surian

Botter

et al. 2020

Hydrol. Earth Syst. Sci.

View full text Add to dashboard Cite

Abstract. Most Alpine rivers have undergone significant alterations in flow and sediment regimes. These alterations have notable effects on river morphology and ecology. One option to mitigate such effects is flow regime management, specifically through the reintroduction of channel-forming discharges. The aim of this work is to assess the morphological changes induced in the Piave River (Italy) by two distinct controlled-flood strategies, the first characterized by a single artificial flood per year and the second by higher-magnitude but less frequent floods. This work involved applying a two-dimensional reduced-complexity morphodynamic model (CAESAR-LISFLOOD) to a 7 km long reach, characterized by a braided pattern and highly regulated discharges. Numerical modelling allowed the assessment of morphological changes for four long-term scenarios (2009–2034). The scenarios were defined considering the current flow regime and the natural regime, which was estimated by a stochastic physically based hydrologic model. Changes in channel morphology were assessed by measuring active-channel width and braiding intensity. A comparison of controlled-flood scenarios to a baseline scenario (i.e. no controlled floods) showed that artificial floods had little effect on channel morphology. More channel widening (13.5 %) resulted from the high-magnitude flood strategy than from the application of the other strategy (8.6 %). Negligible change was observed in terms of braiding intensity. The results indicate that controlled floods do not represent an effective solution for morphological recovery in braided rivers with strongly impacted flow and sediment regimes.

show abstract

Section: The Caesar-lisflood Modelmentioning

confidence: 99%

Assessment of the geomorphic effectiveness of controlled floods in a braided river using a reduced-complexity numerical model

Ziliani

Surian

Botter

et al. 2020

Hydrol. Earth Syst. Sci.

View full text Add to dashboard Cite

show abstract

“…Predicting bed load is a difficult task, especially in steep mountain streams, where channel beds are often organized in boulder‐cascade and step‐pool morphologies (Brardinoni & Hassan, 2007; Buffington & Montgomery, 1997; Comiti & Mao, 2012). Modeling the flow over such bed structures is still very challenging (Escauriaza et al, 2017; Saletti et al, 2016), especially when levels of submergence are low (Comiti et al, 2009; Wilcox et al, 2011). Modeling flow and bed load transport in mountain stream is complex because patches of mobile sediments coexist with immobile structures such as steps or isolated boulders (Green et al, 2015; Laronne et al, 2001; Yager et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Controls Over Particle Motion and Resting Times of Coarse Bed Load Transport in a Glacier‐Fed Mountain Stream

et al. 2020

View full text Add to dashboard Cite

Coarse bed load transport is a crucial process in river morphodynamics but is difficult to monitor in mountain streams. Here we present a new sediment transport data set obtained from 2 years of field-based monitoring (2014)(2015) at the Estero Morales, a high-gradient stream in the central Chilean Andes. This stream features step-pool bed geometry and a glacier-fed hydrologic regime characterized by abrupt daily fluctuations in discharge. Bed load was monitored directly using Bunte samplers and by surveying the mobility of passive integrated transponder (PIT) tags. We used the competence method to quantify the effective slope, which is the fraction of the topographical slope responsible for bed load transport. This accounts for only 10% of the topographical slope, confirming that most of the energy is dissipated on macroroughness elements. We used the displacement lengths of PIT tags to analyze displacement lengths and virtual velocity of a wide range of tracer sizes (38-415 mm). Bed load transport in the Estero Morales shown to be size-selective, and the distance between steps influences the displacement lengths of PIT tags. Displacement lengths were also used to derive the statistics of flight distances and resting times. Our results show that the average length of flight scales inversely to grain size. This contradicts Einstein's conjecture about the linear relationship between grain size and intervals between resting periods in a steep step-pool stream in ordinary flood conditions.

show abstract

“…Numerical simulations play a significant role in the understanding of the flow hydrodynamics and scour around hydraulic structures, as they can explore conditions that cannot be reproduced experimentally or are inaccessible for measurement devices, complementing the observations, and providing additional insights into sediment-flow interactions and feedback [84]. In the following, numerical simulation techniques to be applied to supercritical scour processes are discussed, including the coupled hydrodynamics and sediment transport approach and the multi-phase flow approach.…”

Section: Advanced Numerical Tools For Simulation Of Scour In Supercrimentioning

confidence: 99%

Scour at Bridge Foundations in Supercritical Flows: An Analysis of Knowledge Gaps

Link

Mignot

Roux³

et al. 2019

Water

View full text Add to dashboard Cite

The scour at bridge foundations caused by supercritical flows is reviewed and knowledge gaps are analyzed focusing on the flow and scour patterns, available measuring techniques for the laboratory and field, and physical and advanced numerical modeling techniques. Evidence suggests that the scour depth caused by supercritical flows is much smaller than expected, by an order of magnitude compared to that found in subcritical flows, although the reasons for this behavior remain still unclear. Important questions on the interaction of the horseshoe vortex with the detached hydraulic-jump and the wall-jet flow observed in supercritical flows arise, e.g., does the interaction between the flow structures enhance or debilitate the bed shear stresses caused by the horseshoe vortex? What is the effect of the Froude number of the incoming flow on the flow structures around the foundation and on the scour process? Recommendations are provided to develop and adapt research methods used in the subcritical flow regime for the study of more challenging supercritical flow cases.Large-scale supercritical free-surface flows can occur in different environments. Some examples can be found in cases of flooded urban streets, fish-ways, tsunami inland flows, coastal channels, and mountain rivers. This paper focuses on the flow and scouring patterns at bridge foundations in rivers with supercritical conditions. The occurrence of supercritical flows in rivers is defined by high longitudinal slopes (>1%) and/or rapid flood waves. Commonly, steep rivers present gravel beds or mixtures of fine and coarse sediments, containing all possible sizes, from clay and silt up to boulders tens of centimeters in size. In dentritic networks, streams with a low Strahler's order (i.e., <3) are steep and produce flash floods but normally possess a small cross-sectional width. Therefore, deck bridges without foundations in these riverbeds are usually selected. At piedmont, however, rivers widen and it is common to observe cross sections with widths over 50 m, where bridge foundations may have to be included. Salient examples of such configurations are often encountered in steep watersheds subjected to heavy rains, such as on the Panamericana Route along Perú and Chile, La Réunion Island (Indian Ocean) in Taiwan or Japan, and also in a few European Alpine piedmont rivers (Figure 1). The examples in Figure 1 clearly highlight that supercritical flows are associated with a significant amount of energy for scouring and dynamic loading of the superstructure. Wood debris can also enhance the risk of pier stability. Such flows thus produce among the worst hydraulic conditions for bridge design. A recent bridge collapse due to scour in a supercritical flow occurred at the Rivière Saint Etienne in the La Réunion island due to cyclone Gamède. This bridge, which connected a road with traffic of 65,000 vehicles per day, collapsed and modified the terrestrial transport route for a long time (Figure 1f,g), thereby producing large economic losses. This event motivated, i...

show abstract

Computational Models of Flow, Sediment Transport and Morphodynamics in Rivers

Cited by 7 publications

References 107 publications

Assessment of the geomorphic effectiveness of controlled floods in a braided river using a reduced-complexity numerical model

Assessment of the geomorphic effectiveness of controlled floods in a braided river using a reduced-complexity numerical model

Controls Over Particle Motion and Resting Times of Coarse Bed Load Transport in a Glacier‐Fed Mountain Stream

Scour at Bridge Foundations in Supercritical Flows: An Analysis of Knowledge Gaps

Contact Info

Product

Resources

About