Use of numerical models to study land-based sedimentation and subsequent nearshore morphological evolution

2008 ◽  
Vol 55 (7-8) ◽  
pp. 601-621 ◽  
Author(s):  
N. Dodd ◽  
A.M. Stoker ◽  
R. Garnier ◽  
G. Vittori ◽  
F. de los Santos ◽  
...  
Keyword(s):  
Numerical Models ◽  
Morphological Evolution

Morphodynamic forecast uncertainty due to bathymetry unknowns

2021 ◽  
Author(s):  
Xavier Sánchez-Artús ◽  
Vicente Gracia ◽  
Manuel Espino Infantes ◽  
Agustín Sánchez-Arcilla Conejo
Keyword(s):  
Surf Zone ◽  
Energy Content ◽  
Numerical Models ◽  
Morphological Evolution ◽  
Morphological Response ◽  
Statistical Characterization ◽  
Morphodynamic Modelling ◽  
Coastal Risks ◽  
Rapid Deployment ◽  
Bathymetric Changes

<p>Operational morphodynamic modelling is becoming an attractive tool for managers to forecast and reduce coastal risks. The development of highly sophisticated numerical models during the last decades has underpinned the simulation of beach morphological evolution due to wave impacts. However, there are still some fundamental aspects, such as the bathymetric uncertainty, that needs to be regularly updated in the modelling chain to avoid a worthless forecast. It is also very well known that the surf zone is the most highly dynamic area although the bathymetry changes between certain limits. In this work, we explore the influence of bathymetric changes in morphodynamic forecasts. XBEACH is used to model the morphological response of a dissipative urban low-lying sandy coastal stretch (Barcelona, Spain) for different forecasted storms to determine the uncertainty bands of predicted coastal erosion and flooding. We consider as benchmarks the results of XBEACH simulations fed with the bathymetric information taken from existing nautical charts. An analysis of the possible beach states of the studied area following the Wright and Short (1984) is later performed to determine a range of topo-bathymetric configurations that will be used to run the model again. These new simulations are used to determine the uncertainty of the erosion and flooding results. The energy content of the storm in terms of intensity and duration uncertainty is also considered in the analysis. The proposed ensemble approach will serve to determine the likelihood of the modelling forecast outputs. Such statistical characterization is aligned with ensemble forecasting in meteo-oceanographic fields and will provide robust information for coastal decision making, for instance when considering proactive rapid deployment measures against a forecasted storm.</p>

scholarly journals A 2D HLL-based weakly coupled model for transient flows on mobile beds

2020 ◽  
Vol 22 (5) ◽  
pp. 1351-1369
Author(s):  
Robin Meurice ◽  
Sandra Soares-Frazão
Keyword(s):  
Numerical Models ◽  
Morphological Evolution ◽  
Coupled Model ◽  
Dam Break ◽  
Water Levels ◽  
Test Cases ◽  
Transient Flows ◽  
Dam Breaks ◽  
Weakly Coupled ◽  
High Interaction

Abstract We propose a finite-volume model that aims at improving the ability of 2D numerical models to accurately predict the morphological evolution of sandy beds when subjected to transient flows like dam-breaks. This model solves shallow water and Exner equations with a weakly coupled approach while the fluxes at the interfaces of the cells are calculated thanks to a lateralized HLLC flux scheme. Besides describing the model, we ran it for four different test cases: a steady flow on an inclined bed leading to aggradation or degradation, a dam-break leading to high interaction between the flow and the bed, a dam-break with a symmetrical enlargement close to the gate and a dam-break in a channel with a 90° bend. The gathered results are discussed and compared to an existing fully coupled approach based on HLLC fluxes. Although both models equally perform regarding water levels, the weakly coupled model looks to better predict the bed evolution for the four test cases. In particular, its results are not affected by an excessive numerical diffusion encountered by the coupled model. Moreover, it usually better estimates the amplitudes of the maximum deposits and scours. It is also more stable when subject to high bed–flow interaction.

scholarly journals Determining the Plio-Quaternary uplift of the southern French massif-Central; a new insights for intraplate orogen dynamics

2019 ◽  
Author(s):  
Oswald Malcles ◽  
Philippe Vernant ◽  
Jean Chéry ◽  
Pierre Camps ◽  
Gaël Cazes ◽  
...  
Keyword(s):  
Numerical Models ◽  
Morphological Evolution ◽  
Vertical Motion ◽  
French Massif Central ◽  
Dynamic Topography ◽  
Active Deformation ◽  
Massif Central ◽  
The North ◽  
Cave System ◽  
Clay Deposits

Abstract. The evolution of intra-plate orogens is still poorly understood. Yet, this is of major importance for understanding the Earth and plate dynamic, as well as the link between surface and deep geodynamic processes. The French Massif Central is an intraplate orogen with a mean elevation of 1000 m, with the highest peak elevations ranging from 1500 m to 1885 m. However, active deformation of the region is still debated due to scarce evidence either from geomorphological or geophysical (i.e. geodesy and seismology) data. Because the Cévennes margin allows the use of karst sediments geochronology and morphometrical analysis, we study the vertical displacements of that region: the southern part of the French Massif-Central. Geochronology and morphometrical results, helped with lithospheric-scale numerical modelling, allow, then, a better understanding of this intraplate-orogen evolution and dynamic. Using the ability of the karst to durably record morphological evolution, we first quantify the incision rates. We then investigate tilting of geomorphological benchmarks by means of a high-resolution DEM. We finally use the newly quantified incision rates to constrain numerical models and compare the results with the geomorphometric study. We show that absolute burial age (10Be/26Al on quartz cobbles) and the paleomagnetic analysis of karstic clay deposits for multiple cave system over a large elevation range correlate consistently. This correlation indicates a regional incision rate of 83.4 +17.3/−5.4 m Ma−1 during the last ca 4 Myrs (Plio-Quaternary). Moreover, we point out through the analysis of 55 morphological benchmarks that the studied region has undergone a regional southward tilting. This tilting is expected as being due to a differential vertical motion between the north and southern part of the studied area. Numerical models show that erosion-induced isostatic rebound can explain up to two-thirds of the regional uplift deduced from dating technics and are consistent with the southward tilting obtain from morphological analysis. We presume that the remaining part is related to dynamic topography or thermal isostasy due to the Massif Central plio-quaternary magmatism.

scholarly journals Determining the Plio-Quaternary uplift of the southern French Massif Central; a new insight for intraplate orogen dynamics

Solid Earth ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 241-258 ◽  
Author(s):  
Oswald Malcles ◽  
Philippe Vernant ◽  
Jean Chéry ◽  
Pierre Camps ◽  
Gaël Cazes ◽  
...  
Keyword(s):  
High Resolution ◽  
Numerical Models ◽  
Morphological Evolution ◽  
Vertical Motion ◽  
French Massif Central ◽  
Dynamic Topography ◽  
Active Deformation ◽  
Massif Central ◽  
Clay Deposits ◽  
Triggering Process

Abstract. The evolution of intraplate orogens is still poorly understood. Yet, it is of major importance for understanding the Earth and plate dynamics, as well as the link between surface and deep geodynamic processes. The French Massif Central is an intraplate orogen with a mean elevation of 1000 m, with the highest peak elevations ranging from 1500 to 1885 m. However, active deformation of the region is still debated due to scarce evidence either from geomorphological or geodetic and seismologic data. We focus our study on the southern part of the Massif Central, known as the Cévennes and Grands Causses, which is a key area to study the relationship between the recent geological deformation and landscape evolution. This can be done through the study of numerous karst systems with trapped sediments combined with the analysis of a high-resolution digital elevation model (DEM). Using the ability of karst to durably record morphological evolution, we first quantify the incision rates. We then investigate tilting of geomorphological benchmarks by means of a high-resolution DEM. We finally use the newly quantified incision rates to constrain numerical models and compare the results with the geomorphometric study. We show that absolute burial age (10Be∕26Al on quartz cobbles) and the paleomagnetic analysis of karstic clay deposits for multiple cave system over a large elevation range correlate consistently. This correlation indicates a regional incision rate of 83 +17/-5 m Ma−1 during the last ca. 4 Myr (Pliocene–Quaternary). Moreover, we point out through the analysis of 55 morphological benchmarks that the studied region has undergone a regional southward tilting. This tilting is expected as being due to a differential vertical motion between the northern and southern part of the studied area. Numerical models show that erosion-induced isostatic rebound can explain up to two-thirds of the regional uplift deduced from the geochronological results and are consistent with the southward tilting derived from morphological analysis. We presume that the remaining unexplained uplift is related to dynamic topography or thermal isostasy due to the Massif Central Pliocene–Quaternary magmatism. Integrating both geochronology and morphometrical results into lithospheric-scale numerical models allows a better understanding of this intraplate–orogen evolution and dynamic. We assume that the main conclusions are true to the general case of intraplate deformation. That is to say, once the topography has been generated by a triggering process, rock uplift is then enhanced by erosion and isostatic adjustment leading to a significant accumulation of mainly vertical deformation.

scholarly journals Modelling the evolution of pulsar wind nebulae

2013 ◽  
Vol 32 (1) ◽  
Author(s):  
Michael Vorster
Keyword(s):  
Field Strength ◽  
Numerical Models ◽  
Morphological Evolution ◽  
Pulsar Wind Nebulae ◽  
Pulsar Wind

Using numerical models, the influence of factors such as agnetic field strength on the evolution of pulsar wind ebulae can be determined. This includes the morphological evolution as well as the evolution of the type of light emitted and the corresponding intensity.

scholarly journals Artificial Nourishments Effects on Longshore Sediments Transport

2021 ◽  
Vol 9 (3) ◽  
pp. 240
Author(s):  
Ana Margarida Ferreira ◽  
Carlos Coelho
Keyword(s):  
Sediment Transport ◽  
Numerical Models ◽  
Morphological Evolution ◽  
Temporal Distribution ◽  
Intervention Site ◽  
Coastal System ◽  
Longshore Sediment Transport ◽  
Longshore Transport ◽  
Erosion Mitigation ◽  
Artificial Nourishment

Serious erosion problems related to significant negative sediments budgets in the coastal systems are referred worldwide. Artificial nourishments are a coastal erosion mitigation strategy that allow for a decrease in those negative budgets by adding sediment to the coastal system. Thus, it is essential to understand and adequately model the shoreline response after a nourishment operation, in order to support the definition of the best intervention scenarios. The main goal of this work was to study the artificial nourishment effects on the longshore sediment transport and consequently on the morphological evolution at the intervention site and nearby areas, in a time horizon of 5 years. The longshore transport of the nourished sediments was evaluated, aiming to contribute to the evaluation of the sediment’s permanence at the deposition site and the frequency required for new nourishments. The shoreline evolution numerical long-term configuration (LTC) model was applied in order to evaluate the spatial and temporal distribution of the nourished sediments along the coast, considering different types of beaches and incident wave climates. The adopted approach is generic and supported by simple numerical models, which can be useful for preliminary site-specific evaluations. The results show that the nourishment impact is mainly observed nearby the intervention site. It is highlighted that higher longshore sediment transport rates are associated with more energetic wave climates, but not necessarily with incident waves more oblique to the shoreline.

scholarly journals Forces Driving the Morphological Evolution of a Mud-Capped Dredge Pit, Northern Gulf of Mexico

Water ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 1001 ◽  
Author(s):  
Jiaze Wang ◽  
Kehui Xu ◽  
Chunyan Li ◽  
Jeffrey Obelcz
Keyword(s):  
Gulf Of Mexico ◽  
Observational Data ◽  
Mississippi River ◽  
Numerical Models ◽  
Morphological Evolution ◽  
Suspended Sediments ◽  
Weather Conditions ◽  
Sediment Concentration ◽  
Northern Gulf Of Mexico ◽  
Island Restoration

Sandy sediments preserved as paleo-channel fill on the inner shelf, some of which are overlain by modern muds, have been mined for barrier island restoration along the northern Gulf of Mexico. These mined areas have been termed “mud-capped” dredge pits. The processes governing the morphological evolution of the pits are poorly constrained due to limited observational data. Physical oceanographic (e.g., currents and waves) and sedimentary data were collected at Sandy Point dredge pit offshore Plaquemines Parish, Louisiana in summer 2015. Currents outside the pit flowed southward and/or southeastward at speeds of 8–20 cm/s, while currents inside the pit had speeds less than 2 cm/s with no clear dominant direction. Wave heights detected inside the pit were less than 0.4 m. A high turbidity layer with suspended sediment concentration around 4 g/L was observed above the pit floor, and its thickness was ~0.5 m. With observational data as input, three 2–D numerical models were employed to predict pit morphological responses, including pit infilling, margin erosion and slope change. The model results suggest that resuspension events were rare on the seafloor adjacent to the pit under summer fair weather conditions. Modeled pit margin erosion was very limited. With little resuspension of seafloor sediment locally, weak margin erosion and stable pit walls, the dominant process governing pit evolution was infilling sourced by the deposition of suspended sediments from the Mississippi River plume.

scholarly journals Coupled finite-volume scheme with adapted Augmented Roe scheme for simulating morphological evolution in arbitrary cross-sections

2018 ◽  
Vol 20 (5) ◽  
pp. 1111-1130 ◽  
Author(s):  
F. Franzini ◽  
S. Soares-Frazao
Keyword(s):  
Finite Volume ◽  
Cross Sections ◽  
Morphological Changes ◽  
Numerical Models ◽  
Morphological Evolution ◽  
Finite Volume Scheme ◽  
Steady Flows ◽  
One Dimensional ◽  
Volume Scheme ◽  
Transient Flows

Abstract A new coupled finite-volume scheme based on the Augmented Roe solver adapted to simulate morphological evolution of arbitrary cross-sections is presented. In pure hydrodynamic conditions, the Augmented Roe scheme has proven to provide accurate results and a constant discharge in steady-flow conditions. Here, this scheme is extended to solve the one-dimensional Saint-Venant–Exner system of equations written for arbitrary cross-sections. Therefore, new eigenvalues and source-term calculations are proposed to account for the irregular shape of the cross-sections. The performances of the proposed scheme are assessed by comparison with three different one-dimensional numerical models aimed at simulating morphological changes, with coupled or uncoupled approaches, and based on HLL or Roe-based flux calculations. Numerous test cases were examined, including water at rest, steady flows and transient flows for which experimental results exist. The results show that the proposed scheme provides stable and accurate results for a wider range of situations than is available with other classical models.

A quantitative image analysis method for the determination of cocontinuity in polymer blends

1993 ◽  
Vol 51 ◽  
pp. 894-895
Author(s):  
William A. Heeschen
Keyword(s):  
Image Analysis ◽  
Polymer Blends ◽  
Quantitative Measurement ◽  
Morphological Evolution ◽  
Phase Ratio ◽  
Irregular Shapes ◽  
Quantitative Image ◽  
Discrete Domains ◽  
A Domains

Two new morphological measurements based on digital image analysis, CoContinuity and CoContinuity Balance, have been developed and implemented for quantitative measurement of morphology in polymer blends. The morphology of polymer blends varies with phase ratio, composition and processing. A typical morphological evolution for increasing phase ratio of polymer A to polymer B starts with discrete domains of A in a matrix of B (A/B < 1), moves through a cocontinuous distribution of A and B (A/B ≈ 1) and finishes with discrete domains of B in a matrix of A (A/B > 1). For low phase ratios, A is often seen as solid convex particles embedded in the continuous B phase. As the ratio increases, A domains begin to evolve into irregular shapes, though still recognizable as separate domains. Further increase in the phase ratio leads to A domains which extend into and surround the B phase while the B phase simultaneously extends into and surrounds the A phase.

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