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Clint Dawson - One of the best experts on this subject based on the ideXlab platform.
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discontinuous galerkin methods for a dispersive wave hydro morphodynamic model with bed load transport
Computer Methods in Applied Mechanics and Engineering, 2021Co-Authors: Kazbek Kazhyken, Juha Videman, Clint DawsonAbstract:Abstract A dispersive wave hydro-morphodynamic model coupling the Green–Naghdi equations (the hydrodynamic part) with the sediment continuity Exner equation (the morphodynamic part) is presented. Numerical solution algorithms based on discontinuous Galerkin finite element discretizations of the model are proposed. The algorithms include both coupled and decoupled approaches for solving the hydrodynamic and morphodynamic parts simultaneously and separately from each other, respectively. The Strang operator splitting technique is employed to treat the dispersive terms separately, and it provides the ability to ignore the dispersive terms in specified regions, such as surf zones. Algorithms that can handle wetting–drying and detect wave breaking are presented. The numerical solution algorithms are validated with numerical experiments to demonstrate the ability of the algorithms to accurately resolve hydrodynamics of solitary and regular waves, and morphodynamic changes induced by such waves. The results indicate that the model has the potential to be used in studies of coastal Morphodynamics driven by dispersive water waves, given that the hydrodynamic part resolves the water motion and dispersive wave effects with sufficient accuracy up to swash zones, and the morphodynamic model can capture the major features of bed erosion and deposition.
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discontinuous galerkin methods for a dispersive wave hydro morphodynamic model with bed load transport
arXiv: Numerical Analysis, 2020Co-Authors: Kazbek Kazhyken, Juha Videman, Clint DawsonAbstract:A dispersive wave hydro-morphodynamic model coupling the Green-Naghdi equations (the hydrodynamic part) with the sediment continuity Exner equation (the morphodynamic part) is presented. Numerical solution algorithms based on discontinuous Galerkin finite element discretizations of the model are proposed. The algorithms include both coupled and decoupled approaches for solving the hydrodynamic and morphodynamic parts simultaneously and separately from each other, respectively. The Strang operator splitting technique is employed to treat the dispersive terms separately, and it provides the ability to ignore the dispersive terms in specified regions, such as surf zones. Algorithms that can handle wetting-drying and detect wave breaking are presented. The numerical methods are verified and validated with two numerical experiments: (1) a simulation of water waves in the vicinity of the Faro-Olhao inlet of the Ria Formosa lagoon in Portugal, (2) an experiment that measures the flow and bed morphology induced by a solitary wave over a sloping beach. The results indicate that the model has the potential to be used in studies of coastal Morphodynamics driven by dispersive water waves, given that the hydrodynamic part resolves the water motion and dispersive wave effects with sufficient accuracy up to swash zones, and the morphodynamic model can capture the major features of bed erosion and deposition.
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an a priori error estimate for the local discontinuous galerkin method applied to two dimensional shallow water and morphodynamic flow
Numerical Methods for Partial Differential Equations, 2015Co-Authors: Chris Mirabito, Clint Dawson, Vadym AizingerAbstract:The application of discontinuous Galerkin (DG) methods to the numerical solution of the two- and three-dimensional shallow water equations has seen increased interest over the past decade. In this article, previous work by the second author and several collaborators on the application and analysis of the DG method is extended to coupled shallow water/bed morphology dynamics, also called Morphodynamics. Morphodynamic boundary value problems are used to simultaneously model shallow water hydrodynamics and sediment transport processes in estuarine and coastal systems. The governing equations of interest arise when the two-dimensional Saint-Venant equations are tightly coupled to the corresponding Exner equation. The tight coupling of these two processes presents numerous modeling and analytical challenges. The resulting nonlinear system is incompletely parabolic, and contains a nonconservative product. In this work, some of these analytical challenges are tackled by applying a local discontinuous Galerkin method to the morphodynamic system; the quantities of interest and their gradients are solved separately. A general, semidiscrete finite element formulation is presented, and after justifying some mild assumptions, a new a priori error estimate for the system is derived. © 2014 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 31: 397–421, 2015
Omar Defeo - One of the best experts on this subject based on the ideXlab platform.
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habitat harshness and Morphodynamics life history traits of the mole crab emerita brasiliensis in uruguayan sandy beaches
Marine Biology, 2006Co-Authors: Eleonora Celentano, Omar DefeoAbstract:The habitat harshness hypothesis (HHH) postulates that in reflective beaches the harsh environment forces organisms to divert more energy towards maintenance and they therefore have lower abundance, fecundity, growth and survival rates than in dissipative beaches. Recent investigations have tested this hypothesis through single comparisons of only two beaches, and thus the observed trends in population level variables cannot be attributed incontestably to the beach state, but only to location. Here, abundance, reproduction, recruitment, population structure and body size of the intertidal mole crab Emerita brasiliensis were compared between populations from eight microtidal exposed sandy beaches with contrasting Morphodynamics, sampled bimonthly during 22 months throughout the 180 km Uruguayan Atlantic coast. Physical variables and compound indices of the beach state were used to categorize sandy beaches. The results of this bi-annual large-scale analysis were fully consistent with the predictions of the HHH: abundance (total and population components), duration of the reproduction and recruitment seasons and the individual size of megalops and females of the mole crab E. brasiliensis decreased from dissipative to reflective beaches. This was reflected by linear or, mostly, nonlinear relationships between biological and both physical variables and compound indices of beach state. In conclusion, this multi-beach sampling provides compelling evidence of a consistent response of demographic and life history traits of an intertidal beach species to morphodynamic characteristics.
Kazbek Kazhyken - One of the best experts on this subject based on the ideXlab platform.
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discontinuous galerkin methods for a dispersive wave hydro morphodynamic model with bed load transport
Computer Methods in Applied Mechanics and Engineering, 2021Co-Authors: Kazbek Kazhyken, Juha Videman, Clint DawsonAbstract:Abstract A dispersive wave hydro-morphodynamic model coupling the Green–Naghdi equations (the hydrodynamic part) with the sediment continuity Exner equation (the morphodynamic part) is presented. Numerical solution algorithms based on discontinuous Galerkin finite element discretizations of the model are proposed. The algorithms include both coupled and decoupled approaches for solving the hydrodynamic and morphodynamic parts simultaneously and separately from each other, respectively. The Strang operator splitting technique is employed to treat the dispersive terms separately, and it provides the ability to ignore the dispersive terms in specified regions, such as surf zones. Algorithms that can handle wetting–drying and detect wave breaking are presented. The numerical solution algorithms are validated with numerical experiments to demonstrate the ability of the algorithms to accurately resolve hydrodynamics of solitary and regular waves, and morphodynamic changes induced by such waves. The results indicate that the model has the potential to be used in studies of coastal Morphodynamics driven by dispersive water waves, given that the hydrodynamic part resolves the water motion and dispersive wave effects with sufficient accuracy up to swash zones, and the morphodynamic model can capture the major features of bed erosion and deposition.
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discontinuous galerkin methods for a dispersive wave hydro morphodynamic model with bed load transport
arXiv: Numerical Analysis, 2020Co-Authors: Kazbek Kazhyken, Juha Videman, Clint DawsonAbstract:A dispersive wave hydro-morphodynamic model coupling the Green-Naghdi equations (the hydrodynamic part) with the sediment continuity Exner equation (the morphodynamic part) is presented. Numerical solution algorithms based on discontinuous Galerkin finite element discretizations of the model are proposed. The algorithms include both coupled and decoupled approaches for solving the hydrodynamic and morphodynamic parts simultaneously and separately from each other, respectively. The Strang operator splitting technique is employed to treat the dispersive terms separately, and it provides the ability to ignore the dispersive terms in specified regions, such as surf zones. Algorithms that can handle wetting-drying and detect wave breaking are presented. The numerical methods are verified and validated with two numerical experiments: (1) a simulation of water waves in the vicinity of the Faro-Olhao inlet of the Ria Formosa lagoon in Portugal, (2) an experiment that measures the flow and bed morphology induced by a solitary wave over a sloping beach. The results indicate that the model has the potential to be used in studies of coastal Morphodynamics driven by dispersive water waves, given that the hydrodynamic part resolves the water motion and dispersive wave effects with sufficient accuracy up to swash zones, and the morphodynamic model can capture the major features of bed erosion and deposition.
Michael P. Lamb - One of the best experts on this subject based on the ideXlab platform.
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sediment transport and topographic evolution of a coupled river and river plume system an experimental and numerical study
Journal of Geophysical Research, 2014Co-Authors: Phairot Chatanantavet, Michael P. LambAbstract:Sediment transfer from rivers to the ocean is the fundamental driver of continental sedimentation with implications for carbon burial, land use dynamics, and unraveling global climate change and Earth history from sedimentary strata. Coastal rivers are dynamically coupled to their offshore plumes at the river mouth creating regions of nonuniform flow that can dictate patterns of erosion and deposition both onshore and offshore. However, there are limited experimental and modeling studies on sediment transport and Morphodynamics of coupled river and river plume systems and their response to multiple flood events. To address this knowledge gap, we developed a quasi-2-D, morphodynamic numerical model and conducted exploratory flume experiments in a 7.5 m long flume where a 10 cm wide river channel was connected to a 76 cm wide “ocean basin.” Both the numerical model and the flume results demonstrate that (1) during low-discharge flows, backwater hydrodynamics cause spatial-flow deceleration and deposition in the river channel and the offshore plume area, and (2) during high flows the water surface is drawn down to sea level, resulting in spatial-flow acceleration and bed scour. During high-discharge flows, we also found that the offshore river plume self-channelized owing to both levee formation and bed scour. Our study suggests that coastal rivers may be in a perpetual state of morphodynamic adjustment and highlights the need to link rivers and river plumes under a suite of flow discharges to accurately predict fluvio-deltaic Morphodynamics and connectivity between fluvial sediment sources and marine sinks.
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quantitative bounds on Morphodynamics and implications for reading the sedimentary record
Nature Communications, 2014Co-Authors: Vamsi Ganti, Michael P. Lamb, Brandon McelroyAbstract:Sedimentary rocks are the archives of environmental conditions and ancient planetary surface processes that led to their formation. Reconstructions of Earth’s past surface behaviour from the physical sedimentary record remain controversial, however, in part because we lack a quantitative framework to deconvolve internal dynamics of sediment-transport systems from environmental signal preservation. Internal dynamics of landscapes—a consequence of the coupling between bed topography, sediment transport and flow dynamics (Morphodynamics)—result in regular and quasiperiodic landforms that abound on the Earth and other planets. Here, using theory and a data compilation of morphodynamic landforms that span a wide range of terrestrial, marine and planetary depositional systems, we show that the advection length for settling sediment sets bounds on the scales over which internal landscape dynamics operate. These bounds provide a universal palaeohydraulic reconstruction tool on planetary surfaces and allow for quantitative identification of depositional systems that may preserve tectonic, climatic and anthropogenic signals.
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backwater controls of avulsion location on deltas
Geophysical Research Letters, 2012Co-Authors: Phairot Chatanantavet, Michael P. Lamb, Jeffrey A NittrouerAbstract:River delta complexes are built in part through repeated river-channel avulsions, which often occur about a persistent spatial node creating delta lobes that form a fan-like morphology. Predicting the location of avulsions is poorly understood, but it is essential for wetland restoration, hazard mitigation, reservoir characterization, and delta Morphodynamics. Following previous work, we show that the upstream distance from the river mouth where avulsions occur is coincident with the backwater length, i.e., the upstream extent of river flow that is affected by hydrodynamic processes in the receiving basin. To explain this observation we formulate a fluvial morphodynamic model that is coupled to an offshore spreading river plume and subject it to a range of river discharges. Results show that avulsion is less likely in the downstream portion of the backwater zone because, during high-flow events, the water surface is drawn down near the river mouth to match that of the offshore plume, resulting in river-bed scour and a reduced likelihood of overbank flow. Furthermore, during low-discharge events, flow deceleration near the upstream extent of backwater causes enhanced deposition locally and a reduced channel-fill timescale there. Both mechanisms favor preferential avulsion in the upstream part of the backwater zone. These dynamics are fundamentally due to variable river discharges and a coupled offshore river plume, with implications for predicting delta response to climate and sea level change, and fluvio-deltaic stratigraphy.
Wallinga J. - One of the best experts on this subject based on the ideXlab platform.
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Oblique aggradation: A novel explanation for sinuosity of low-energy streams in peat-filled valley systems
'Wiley', 2017Co-Authors: Candel, Jasper H J, Makaske Bart, Storms J.e.a., Wallinga J.Abstract:Low-energy streams in peatlands often have a high sinuosity. However, it is unknown how this sinuous planform formed, since lateral migration of the channel is hindered by relatively erosion-resistant banks. We present a conceptual model of Holocene morphodynamic evolution of a stream in a peat-filled valley, based on a palaeohydrological reconstruction. Coring, ground-penetrating radar (GPR) data, and 14C and OSL dating were used for the reconstruction. We found that the stream planform is partly inherited from the Late-Glacial topography, reflecting stream morphology prior to peat growth in the valley. Most importantly, we show that aggrading streams in a peat-filled valley combine vertical aggradation with lateral displacement caused by attraction to the sandy valley sides, which are more erodible than the co-evally aggrading valley-fill. Owing to this oblique aggradation in combination with floodplain widening, the stream becomes stretched out as channel reaches may alternately aggrade along opposed valley sides, resulting in increased sinuosity over time. Hence, highly sinuous planforms can form in peat-filled valleys without the traditional Morphodynamics of alluvial bed lateral migration. Improved understanding of the evolution of streams provides inspiration for stream restoration.Applied Geolog
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Oblique aggradation: A novel explanation for sinuosity of low-energy streams in peat-filled valley systems
2017Co-Authors: Candel, Jasper H J, Makaske Bart, Storms J.e.a., Wallinga J.Abstract:Low-energy streams in peatlands often have a high sinuosity. However, it is unknown how this sinuous planform formed, since lateral migration of the channel is hindered by relatively erosion-resistant banks. We present a conceptual model of Holocene morphodynamic evolution of a stream in a peat-filled valley, based on a palaeohydrological reconstruction. Coring, ground-penetrating radar (GPR) data, and 14C and OSL dating were used for the reconstruction. We found that the stream planform is partly inherited from the Late-Glacial topography, reflecting stream morphology prior to peat growth in the valley. Most importantly, we show that aggrading streams in a peat-filled valley combine vertical aggradation with lateral displacement caused by attraction to the sandy valley sides, which are more erodible than the co-evally aggrading valley-fill. Owing to this oblique aggradation in combination with floodplain widening, the stream becomes stretched out as channel reaches may alternately aggrade along opposed valley sides, resulting in increased sinuosity over time. Hence, highly sinuous planforms can form in peat-filled valleys without the traditional Morphodynamics of alluvial bed lateral migration. Improved understanding of the evolution of streams provides inspiration for stream restoration.
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Oblique aggradation: a novel explanation for sinuosity of low-energy streams in peat-filled valley systems
2017Co-Authors: Candel J.h.j., Storms J.e.a., Makaske A., Wallinga J.Abstract:Low-energy streams in peatlands often have a high sinuosity. However, it is unknown how this sinuous planform formed, since lateral migration of the channel is hindered by relatively erosion-resistant banks. We present a conceptual model of Holocene morphodynamic evolution of a stream in a peat-filled valley, based on a palaeohydrological reconstruction. Coring, ground-penetrating radar (GPR) data, and 14C and OSL dating were used for the reconstruction. We found that the stream planform is partly inherited from the Late-Glacial topography, reflecting stream morphology prior to peat growth in the valley. Most importantly, we show that aggrading streams in a peat-filled valley combine vertical aggradation with lateral displacement caused by attraction to the sandy valley sides, which are more erodible than the co-evally aggrading valley-fill. Due to this oblique aggradation in combination with floodplain widening, the stream becomes stretched out as channel reaches may alternately aggrade along opposed valley sides, resulting in increased sinuosity over time. Hence, highly sinuous planforms can form in peat-filled valleys without the traditional Morphodynamics of alluvial bed lateral migration. Improved understanding of the evolution of streams provides inspiration for stream restoration. This article is protected by copyright. All rights reserved.