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The TELEMAC modelling system—special issue
... We consider a simplified numerical model of a (sand) dune on the ground of a channel whose shape and position changes due to flowing water. The given experiment is implemented in Sisyphe 3 [8] using the programming language Fortran 90. Our aim is to determine the sensitivity of the dune's shape with respect to the roughness of the material (sand etc.). ...
... The complete source code is divided into five libraries (bief, special, damocles, paravoid, and sisyphe). The AD-enabled compiler is applied to all of them 8 to generate the corresponding tangent-linear libraries. ...
... contained in the file sisyphe/sisyphe v5p4/sources/sisyphe.f of Sisyphe version 5.48 That is all source code files are compiled into tangent-linear code with only one exception: File lit.f of from library bief must be compiled without differentiation. See Section A.3 for details and how to adapt lit.f manually. ...
... However, a model that is to be used as an engineering tool requires a more objective assessment based on measures of skill. Among existing numerical modelling systems, TELEMAC (Hervouet and Bates, 2000) is one package including modules for the modelling of free surface hydrodynamics, sedimentology , water quality, waves and groundwater flows. The TELEMAC system is developed by the Laboratoire National d'Hydraulique et Environnement (L.N.H.E.), a research department of the French Electricity Board (EDF-DRD), and distributed by SOGREAH. ...
... The validation of TELEMAC conforms to the recommendations of the International Association of Hydraulics Research (IAHR) for the validation of computational models. Moreover, the numerical system has been successfully applied to practical cases for a few years (Hervouet and Bates, 2000). However, these studies involve mainly applications of TELEMAC modules without any comparison between numerical results and field data. ...
... Such modelling systems are typically applied to areas of a few square kilometres over timescales of a few tides. The modelling system TELEMAC contains in particular the TOMAWAC module (Benoit et al., 1996) for calculating the wave propagation and the TELEMAC 2D module (Hervouet and Bates, 2000) for calculating the hydrodynamics. The TOMAWAC module is a third generation phaseaveraged model that describes the evolution of the twodimensional wave energy spectrum in arbitrary conditions of wind, currents and bathymetry, using a finite element formulation. ...
The wave propagation and flow modules of the TELEMAC system have been applied to the Adour River mouth and the adjacent beaches of Anglet (France). The wave propagation has been simulated using the phase-averaged model TOMAWAC. In addition, the phase-resolving REFDIF S model has been also used, as the diffraction of wind waves, which is not taken into account in TOMAWAC, can occur in the vicinity of the River mouth. Next, the hydrodynamics has been simulated using the two-dimensional depth-averaged flow TELEMAC 2D model.The numerical results are compared with field measurements collected in March 2003. Model performance statistics are calculated in order to assess the accuracy of the predictions at six locations. Regarding the computation of the wave propagation, a root mean square error (RMSE) is evaluated for the significant wave height, the mean period and the peak direction of propagation. For the flow computation, a mean absolute error (MAE) is used as it is applicable to vector quantities. A classification is also adopted that categorises the quality of the results.Regarding the significant wave height, the average relative RMSE is of 18.2% for the TOMAWAC computations whereas the error is of 30.8% for the REFDIF S simulations. Concerning the peak wave direction, the RMSE is about 10°. Both models predict the wave direction normal to the shore whereas the experimental parameters are more variable. However, the areas, where energy concentrates, are well reproduced.The classification of errors shows that TELEMAC 2D flow predictions are in a range from excellent to reasonable.
... Open sea boundary conditions were provided, taking into account four semi-diurnal tidal components (M 2 , S 2 , N 2 , K 2 ) and four diurnal tidal components (O 1 , K 1 , P 1, Q 1 ). The two-dimensional finite element model TELEMAC-2D (v.5.5) (HerVouet and bates, 2000) solves the depth averaged Saint-Venant equations. Turbulent viscosity was considered constant over the whole domain. ...
... The two-dimensional finite element model TELEMAC-2D (v.5.5) (HerVouet and bates, 2000) solves the depth averaged Saint-Venant equations. Turbulent viscosity was considered constant over the whole domain. ...
The origin and morphodynamic evolution of linear sand banks have been widely studied in recent years. Several investigations have been carried out in order to understand the influence of tide-related parameters, bathymetry and Coriolis force on sand bank formation and maintenance. However, the effect of waves on the net flux of sediments over the sand banks has often been neglected on grounds of the short duration of significant wave activity compared to that of tidal cycles. Nevertheless, the interaction between wave activity and tidal currents leads to a high increase of bottom shear stress, especially at the sand bank crests and, as a consequence, to an increase of sand tranport. This paper investigates the effects of wave activity on the morphology and morphodynamics of the Kwinte Bank (Belgian shelf). Numerical simulations were carried out under different wave conditions to assess wave influence on sand bank evolution. Model verification involved analysis and comparison with field data collected during two different periods.
The study shows that wave activity is not only responsible for a large increase in sediment transport but also for a change in direction of the net flux of sediments. Moreover, the morphological analysis of several sand banks supports the idea that wave activity might also have an impact on the shape of these sand banks. Wave climate data can be used to study long-term sand bank dynamics.
... Process-based models have proven their use in quantitatively predicting the effects of natural events and human interventions on coastal evolution, e.g. at the Sand Engine (Luijendijk et al., 2017;Hoonhout and de Vries, 2019). Yet, most of these coastal process-based models mainly focus on distinct sub-domains, analysing either the marine (Warren and Bach, 1992;Booij et al., 1999;Hervouet and Bates, 2000;Lesser et al., 2004;Roelvink et al., 2009) or the aeolian (Durán et al., 2010;Keijsers et al., 2016;Hoonhout and de Vries, 2017) domains separately. Consequently, these models often neglect the interactions between aeolian and marine subdomains. ...
Quantitative predictions of marine and aeolian sediment transport in the nearshore–beach–dune system are important for designing Nature-Based Solutions (NBS) in coastal environments. To quantify the impact of the marine-aeolian interactions on shaping NBS, we present a framework coupling three existing process-based models: Delft3D Flexible Mesh, SWAN and AeoLiS. This framework facilitates the continuous exchange of bed levels, water levels and wave properties between numerical models focussing on the aeolian and marine domain. The coupled model is used to simulate the morphodynamic evolution of the Sand Engine mega-nourishment. Results display good agreement with the observed aeolian and marine volumetric developments, showing similar marine-driven erosion from the main peninsula and aeolian-driven infilling of the dune lake. To estimate the magnitude of the interactions between aeolian and marine processes, a comparison between the simulated morphological development by the coupled and stand-alone models was made. This comparison shows that aeolian sediment transport to the foredune, i.e. 214,000 m3 over 5 years, extracts sediment from the marine domain. As a result, the alongshore redistribution of sediment from the main peninsula by marine-driven processes decreased by 70,000 m3, representing 1.7% of the total marine-driven dispersion. From the aeolian perspective, marine-driven deposition and erosion reshape the cross-shore profile, controlling the supply-limited aeolian sediment transport and the magnitude of sediment deposition in the foredunes. In the region with persistent accretion along the Sand Engine’s southern flank, a higher than average foredune deposition was predicted due to morphological development of the region where sediment is picked up by aeolian transport. Including these marine processes in the coupled model resulted in an increase of 1.3% in foredune growth in year 1 and up to 6.7% in year 5 along this accretive section. At the northern flank, where the developing lagoon and tidal channel provided increased shelter to the supratidal beach, predicted foredune deposition reduced up to −11.5% over the evaluation period. Our findings show that both aeolian and marine transports impact reshaping the nourished sand, where developments in one domain affect the other. The study findings echo that the interplay between aeolian- and marine-driven morphodynamics could play a relevant role when predicting sandy NBS.
... Tidal currents can reach up to speeds of 1.2 m/s in these areas, they are the main drivers behind sediment transport, wind induced drag forces also play their own role in the processes (Fettweis and Eynde, 2003;(Baeye, 2012); (Van Lancker, et al., 2012).The seasonal seawater temperature variation are between 5°C and 20°C (The Flemish Banks Monitoring Network, 2015). In terms of salinity, low concentration zones occur in regions where sea water mixes with the Scheldt, Rhine, Seine and Meuse (Hervouet and Bates, 2000;Mastenbroek et al., 1993;Lacroix et al., 2004. The pH values in the area varies between 7.95 and 8.25 (Gypens et al., 2011). ...
The thesis presents efforts to simulate tides in the Belgian Continental Shelf (BCS) using the numerical model TELEMAC-2D.
... The sediment transport model sisyphe and the hydrodynamic model Telemac2D are internally coupled where at each time step, sisyphe receives the spatial distribution of the main hydrodynamic variables: water depth h, horizontal depth-averaged flow velocity components V x and V y , and bed shear stress τ calculated by the hydrodynamic model. Telemac2D has been validated for various analytical, experimental and real-field cases (Hervouet and Bates, 2000). ...
Hydro-morphological response of the meandering channels to different arrangement of groynes is investigated using a depth-averaged 2D numerical model. A coupled model of flow and bed morphology is formulated and validated before applying to two laboratory scale sine-generated meandering channels of different sinuosity and deflection angle. Two positions-one starting exactly from the outer bank apex and the other starting from downstream of the outer bank apex and two orientation-one at 90°and the other at 120°t o the bankline were investigated. Results revealed that in low sinuosity channel, groynes positioned downstream of the outer bank apex whereas in higher sinuosity channel groynes at apex are more effective in reducing the scour depth at the groynes tip, shifting high-velocity and high near-bank shear stress away from the banks. The analysis also showed that the morphology and flow field were more sensitive to the change in groynes position than their orientation.
... Since these data are necessary for our analysis, the reconstruction of the flood event is performed by means of TELEMAC-2D, a fully 2-D hydrodynamic model which solves the 2-D shallow water Saint-Venant equations using the finite-element method within a computational mesh of triangular elements (see Galland et al., 1991;Hervouet and Bates, 2000, for details). This computational model complies with the validation protocol by the International Association for Hydro-Environment Engineering and Research (IAHR) and has been successfully applied to case studies around the globe (Hervouet and Bates, 2000;Brière et al., 2007). Concerning the inundation event, the dynamics of the wetting front were strongly influenced by the presence of topographic discontinuities (e.g., road embankments, artificial as well as natural channels belonging to the minor stream network; see D' Alpaos et al., 2014). ...
Flood loss models are one important source of uncertainty in flood risk
assessments. Many countries experience sparseness or absence of comprehensive
high-quality flood loss data, which is often rooted in a lack of protocols and
reference procedures for compiling loss datasets after flood events. Such
data are an important reference for developing and validating flood loss
models. We consider the Secchia River flood event of January 2014, when a
sudden levee breach caused the inundation of nearly 52 km2 in northern
Italy. After this event local authorities collected a comprehensive flood
loss dataset of affected private households including building footprints and
structures and damages to buildings and contents. The dataset was enriched with
further information compiled by us, including economic building values,
maximum water depths, velocities and flood durations for each building. By
analyzing this dataset we tackle the problem of flood damage estimation in
Emilia-Romagna (Italy) by identifying empirical uni- and multivariable loss
models for residential buildings and contents. The accuracy of the proposed
models is compared with that of several flood damage models reported in the
literature, providing additional insights into the transferability of the
models among different contexts. Our results show that (1) even simple
univariable damage models based on local data are significantly more
accurate than literature models derived for different contexts;
(2) multivariable models that consider several explanatory variables
outperform univariable models, which use only water depth. However,
multivariable models can only be effectively developed and applied if
sufficient and detailed information is available.
... Furthermore, hydrodynamic-numerical models exist for this selected test stretch. These models are an unsteady 1D hydrodynamic-numerical model CasCade which solves the one-dimensional Saint-Venant equations (shallow water equations) with an implicit finite difference scheme and a 2D hydrodynamic-numerical model (TELEMAC-2D, Hervouet and Bates, 2000). This finite element code solves the depth-averaged Navier-Stokes equations on irregular meshes (average grid spacing of about 4 -8 m). ...
The PROMINENT project co-funded under the H2020 program aims to develop innovations in inland waterway transport. It focusses on several areas: a) the introduction of technologies to improve energy efficiency and to reduce pollutant emissions, b) certification and (on-board) monitoring and c) professional qualification. This publication focusses on the possibilities of digital solutions and on-board monitoring in order to evaluate the operational performance of vessels and to develop tools for the skipper for energy-efficient navigation. An on-board monitoring measures speed and location, fuel consumption, power distribution, NO x and CO 2 emissions. This data is continuously sent to a central database for the evaluation and benchmarking. It can also be used to optimize the efficiency of the ship driveline. The digital solution for efficient navigation combines on-board monitoring with the information from river models in order to provide the skipper with up to date information on sailing speed, arrival time and fuel consumption on each trip.
... The red dotted line in both graphs is the measured data while green is a moving average over 100 m of the measured data. The measured data is compared to the flow velocities calculated numerically with TELEMAC 2D, Hervouet and Bates (2000), Wurms et al., (2010), which are represented by the blue line in the graphs below. While the Rhine discharge at the time of the measurement amounted to 2770 m³/s on average, the comparative data resulting from TELEMAC calculations corresponds to a discharge of 2750 m³/s. ...
The European Union (EU) project PROMINENT - Promoting Innovation in the Inland Waterways Transport (IWT) Sector - which was launched in May 2015, is a multiannual research and innovation programme for inland navigation, funded by the Horizon 2020 programme of the European Union. Running until April 2018, and involving a number of important stakeholders of the IWT sector of the EU, the project focusses on:
massive transition towards efficient and clean vessels by developing cost-effective solutions applicable to 70 % of the EU fleet and reduction of the corresponding implementation costs by 30 %;
certification and monitoring of emission performance and development of innovative regimes;
harmonisation and modernisation of professional qualifications and the stimulation of the further integration of IWT into sustainable transport chains.
Building upon the identification of the most promising greening technologies and the technical developments carried out in the project, several pilots were set-up and carried out, delivering a great number of interesting results of significance to the IWT sector. The pilots under consideration were:
monitoring of exhaust gas emissions and operational profiles on existing, innovative vessels;
demonstration of performance of standardised retrofit diesel after-treatment systems;
demonstration of energy-efficient navigation;
usage of liquefied natural gas (LNG) in inland waterway vessels – development and testing of a total hydrocarbon (90 % methane) reduction package, forming together with the elaborations on design improvements in WP2 of PROMINENT the basis for compliance with the emission limits of the Stage V of the Non Road Mobile Machinery (NRMM) Directive (Regulation (EU) 2016/1628) till 2020;
logistics education, comprising usage of simulations and e-learning, demonstration of electronic Service Record Book (e-SRB) and electronic Logbook (e-Logbook), as well as demonstration of a Pilot Community of Practice (CoP) in logistics education.
In this report, the final results relating to the pilots listed above are presented and discussed, amending the mid-term evaluation report PROMINENT D6.2 (2017).
... Bed roughness has been mapped by an ADCP (e.g., [28]), and high-resolution bathymetry and granulometry samples have been used by Huybrechts et al. [29] to derive bed roughness maps used in a TELEMAC model (cf. [30,31]). Recently, the use of high-resolution multibeam sonar has provided bathymetric data at a resolution of less than 1 m and revealed the details of sea bed features (e.g., DORIS (http://www.dorsetwildlifetrust.org.uk/doris.html)) ...
The paper is motivated by a present lack of clear model performance guidelines for shelf sea and estuarine modellers seeking to demonstrate to clients and end users that a model is fit for purpose. It addresses the common problems associated with data availability, errors, and uncertainty and examines the model build process, including calibration and validation. It also looks at common assumptions, data input requirements, and statistical analyses that can be applied to assess the performance of models of estuaries and shelf seas. Specifically, it takes account of inherent modelling uncertainties and defines metrics of performance based on practical experience. It is intended as a reference point both for numerical modellers and for specialists tasked with interpreting the accuracy and validity of results from hydrodynamic, wave, and sediment models.
... The red dotted line in both graphs is the measured data while green is a moving average over 100 m of the measured data. The measured data is compared to the flow velocities calculated numerically with TELEMAC 2D, Hervouet and Bates (2000), Wurms et al., (2010), which are represented by the blue line in the graphs below. While the Rhine discharge at the time of the measurement amounted to 2770 m³/s on average, the comparative data resulting from TELEMAC calculations corresponds to a discharge of 2750 m³/s. ...
The European Union (EU) project PROMINENT - Promoting Innovation in the Inland Waterways Transport (IWT) Sector - which was launched in May 2015, is a multiannual research and implementation programme for inland navigation, funded by the Horizon 2020 programme of the European Union. Running until April 2018, and involving a number of important stakeholders of the IWT sector of the EU, the project focusses on:
massive transition towards efficient and clean vessels by developing cost-effective solutions applicable to 70 % of the EU fleet and reduction of the corresponding implementation costs by 30 %; certification and monitoring of emission performance and development of innovative regimes; harmonisation and modernisation of professional qualifications and the stimulation of the further integration of IWT into sustainable transport chains.
Building upon the identification of the most promising greening technologies and the technical developments carried out in the project, several pilots were set-up and started, delivering already a great number of interesting results of significance to the IWT sector. The pilots under consideration are:
monitoring of exhaust gas emissions and operational profiles on existing, innovative vessels; demonstration of performance of standardised retrofit diesel after-treatment systems; demonstration of energy-efficient navigation; usage of liquefied natural gas (LNG) in inland waterway vessels – compliance with the emission limits of the Stage V of the Non Road Mobile Machinery (NRMM) Directive (Regulation (EU) 2016/1628); logistics education, comprising usage of simulations, demonstration of electronic Service
Record Book (e-SRB) and electronic Logbook (e-Logbook), as well as demonstration of a Pilot Community of Practice (CoP) in logistics education.
In this report, a great number of first results is presented and discussed relating to the pilots listed above. The objective of this report is to show what has been already achieved in the pilots and which activities will be carried out further. The pilot activities will continue, and further results will become available until the final stage of the project. Considering the feedback of stakeholders, the final results shall be presented in the PROMINENT deliverable D6.4 - Final pilot review report.
... Forms B collected from authorities for the purpose of compensation do not include data on hydraulic variables, such as water depth, water velocity, etc. Being these data necessary for the aim of our analysis, the reconstruction of the flood event was performed by means of a 2D finite element numerical model (Telemac-2D) a fully-2D hydrodynamic model which solves the 10 2D shallow water Saint Venant equations using the finite-element method within a computational mesh of triangular elements (see Galland et al., 1991;Hervouet and Bates, 2000, for details). This computational model complies with the validation protocol by the International Association of Hydraulics Research (IAHR) and has been successfully applied to case studies around the globe (Hervouet and Bates, 2000;Brière et al., 2007). ...
Simplified flood loss models are one important source of uncertainty in flood risk assessments. Many countries experience sparseness or absence of comprehensive high-quality flood loss data sets which is often rooted in a lack of protocols and reference procedures for compiling loss data sets after flood events. Such data are an important reference for developing and validating flood loss models. We consider the Secchia river flood event of January 2014, when a sudden levee-breach caused the inundation of nearly 52 km² in Northern Italy. For this event we compiled a comprehensive flood loss data set of affected private households including buildings footprint, economic value, damages to contents, etc. based on information collected by local authorities after the event. By analysing this data set we tackle the problem of flood damage estimation in Emilia-Romagna (Italy) by identifying empirical uni- and multi-variable loss models for residential buildings and contents. The accuracy of the proposed models is compared with those of several flood-damage models reported in the literature, providing additional insights on the transferability of the models between different contexts. Our results show that (1) even simple uni-variable damage models based on local data are significantly more accurate than literature models derived for different contexts; (2) multi-variable models that consider several explanatory variables outperform uni-variable models which use only water depth. However, multi-variable models can only be effectively developed and applied if sufficient and detailed information is available.
... A tidal barrage is likely also to cause a change in the tidal volume before the estuary settles to a new equilibrium. To quantify the possible changes in sediment transport and, hence, in the morphology, both in the short term (~ 1 year) and in the long term (~ 10 years), computer modelling work is being carried out, based on the TELEMAC suite (Hervouet and Bates, 2000). The TELEMAC model system includes a wave module (Tomawac), a hydrodynamic module (Telemac-2d) and a morphodynamic module (Sisyphe). ...
... Although modern advances to coastal models [i.e. Xbeach (Roelvink et al., 2009) or Telemac (Hervouet & Bates, 2000)] have enabled a degree of either spatial (or temporal) sediment tracking modules, the computational costs are often so expensive that they are seldom enabled for modelling timescales 1 longer than a few hours to days. Therefore, a quantifiable understanding of the variability exhibited by sandy sediments in a response to changes in the hydrodynamic conditions can aid these modelling efforts. ...
Grain size and sorting represent two key parameters when characterising sediments or modelling beach morphology and sediment transport. Traditionally, an average value for grain size or sorting is often assumed for the entire area, determined from only a few sediment samples, ignoring any spatial (or temporal) variability in sediment characteristics. This contribution uses a data set of physical surface sediment samples from 53 beach locations around the south-west peninsula of the United Kingdom, in addition to bi-monthly, high spatial resolution (mean 240 samples) digital grain-size surveys from a high-energy, oceanic, sandy beach (Perranporth, North Cornwall). Systematic spatial variations in grain size and sorting were consistently observed in the seaward direction across the intertidal zone of sandy beaches, with grain sizes coarsening and sorting improving by up to 51.7% and 64.3%, respectively. This variability was deterministically related to the time-averaged, antecedent-adjusted energy dissipated by breaking waves, with the observed maximum grain sizes and sorting values correlating with the location of peak wave energy dissipation (r2 = 0.998, p < 0.01). This article is protected by copyright. All rights reserved.
... The numerical toolbox encompassed the hydrodynamic and sediment transport modelling systems applying one domain (grid): UnTRIM2007 (CASULLI and ZANOLLI 2002), TELEMAC (HERVOUET 2000) and MARINA (MILBRADT, smile consult) (Fig. 12 left) and a two model domain concept operated by DELFT3D (LESSER et al. 2004;Fig. 12, right). ...
The main objective of the multidisciplinary research project "AufMod" (2009-2012) was the development of model-based tools for analyzing long-term sediment transport and morphodynamic (MD) processes in the German Bight. AufMod aimed at bringing together marine geoscientists and coastal engineers to build up consistent bathymetric and sedimentological databases and to compare different numerical models using the same data input and model grid with respect to uncertainties in their results. AufMod provides a suite of consistent annual bathymetries as well as initial sediment parameters which can be used by numerical MD models for further analyses. Different patchy datasets from bathymetric survey campaigns since 1948 have been compiled and have undergone a sophisticated postprocessing procedure to overcome inconsistencies arising from the use of different echosounding techniques, vessels, tidal correction and so on. For the first time, data on grain size distribution have been composed for the entire North Sea including the German Bight in order to analyze geomorphological processes and to calculate sediment input parameters for morphodynamic modelling. By establishing a so-called "Functional Seabed-Model" consistent annual bathymetries and initial sediment distribution and composition (grain size distribution) have been made available together with their spatial and temporal uncertainties. The morphodynamic numerical model simulations cover a time span from 1996 to 2008. They are based on natural processes and take account of the whole variability of tides, external surge, river run-off, wind and waves. "AufMod" provides a suite of consistent annual bathymetries as well as initial sediment parameters which can be used by numerical MD models for further analyses. By using the same model grids the strength and weakness of the different numeric models can be evaluated and their uncertainties can be assessed. The morphodynamic model results provide a first comprehensive impression of the resulting sediment transport pathways in the German Bight. Further model runs have focused on the sensitivity of sediment transport and the morphological response due to wind forcing, mean sea level rise and variation in porosity.
... Although not specifically developed to deal with climate change impacts, these models can be applied to sector analysis (e.g., shoreline change and storm impact simulations) or to the integrated assessment of coastal vulnerability to SLR.The main examples include Delft3D, developed by Deltares (e.g.,Lesser et al., 2004; Tung et al., 2009;Van der Wegen and Roelvink, 2012), MIKE 2D, and the KUTM (the Kyushu University Tidal Model). Comprehensive morphodynamic modelling systems such as ECOMSed, Mike-21, Delft3D ROMS, and TELEMAC-MASCATE(Hervouet and Bates, 2000; http://www.opentelemac.org) generally include different flow modules (from 1D to 3D), a wave propagation model, and a sand transport model including bed load and suspended load(Villaret et al., 2013; see the example inFig. ...
... These equations are approximated on an irregular or unstructured mesh using the finite element method [32]. TELEMAC-2D has been validated for many analytic, experimental and real-world cases [33,32]. ...
In the pioneering study of the Ishikari River, Japan, Kinoshita (Kinoshita 1957, 1961) described two types of meandering channels: (1) channel with two bars per meander wavelength (one bar per bend), and (2) channel with three or more bars per meander wavelength (multiple bars per bend). Based on the study of Whiting & Dietrich (1993a, b), we assess the capabilities of the Telemac-Mascaret modelling system (2014) to reproduce Two-Dimensional (2D) and Three-Dimensional (3D) flow and morphodynamics structures in large-amplitude meandering channels. The large-amplitude meander setup of Whiting & Dietrich (1993a, b) was shown to be a difficult test for a depth-averaged 2-D model: even if appropriate parameterizations of relevant 3D effects are incorporated into the model, numerical simulations failed to capture some 3D patterns, such as the first well-defined pool observed in the experiments. However, 3D results obtained from the numerical solution of the RANS equations showed that most of the observed flow and morphodynamics patterns (e.g., series of shingled bars with pools along the concave bank, depositional bank fronts along the inner bank) are well captured by the model. In agreement with experimental observations, the bed topography in large amplitude symmetric planforms can be divided into different zones according to the different morphodynamics patterns: a zone with an almost zero bed load discharge and bed evolution, an "alternate bars" zone, a "shingle-bars zone" and a "multiple-pools" zone.
... Following the recommendations proposed by Hardy et al. (2000) and Benjankar and Yager (2012), we made use of a modelling system able to carry out unsteady simulations, to take account of advection and diffusion processes, feedback processes between topography and hydrodynamic variables, and to integrate input suspended-sediment concentration as boundary conditions. According to these requirements, the model that has been set up is based on the open source Telemac hydro-informatic system (release 6.2) (Hervouet and Bates, 2000). The latter allows for dynamically coupling a 2D-shallow water hydrodynamic model -Telemac-2D -and a sediment transport model -Sisyphe. ...
Fine sediments represent an important vector of pollutant diffusion in rivers. When deposited in floodplains and riverbeds, they can be responsible for soil pollution. In this context, this paper proposes a modelling exercise aimed at predicting transport and diffusion of fine sediments and dissolved pollutants. The model is based upon the Telemac hydro-informatic system (dynamical coupling Telemac-2D-Sysiphe). As empirical and semiempirical parameters need to be calibrated for such a modelling exercise, a sensitivity analysis is proposed. An innovative point in this study is the assessment of the usefulness of dissolved trace metal contamination information for model calibration. Moreover, for supporting the modelling exercise, an extensive database was set up during two flood events. It includes water surface elevation records, discharge measurements and geochemistry data such as time series of dissolved/particulate contaminants and suspended-sediment concentrations. The most sensitive parameters were found to be the hydraulic friction coefficients and the sediment particle settling velocity in water. It was also found that model calibration did not benefit from dissolved trace metal contamination information. Using the two monitored hydrological events as calibration and validation, it was found that the model is able to satisfyingly predict suspended sediment and dissolve pollutant transport in the river channel. In addition, a qualitative comparison between simulated sediment deposition in the floodplain and a soil contamination map shows that the preferential zones for deposition identified by the model are realistic.
... These equations are approximated on an irregular or unstructured mesh using the finite element method [32]. TELEMAC-2D has been validated for many analytic, experimental and real-world cases [33,32]. ...
The flow and sediment transport processes near steep streambanks, which are commonly found in meandering, braided, and anastomosing stream systems, exhibit complex patterns that produce intricate interactions between bed and bank morphologic adjustment. Increasingly, multi-dimensional computer models of riverine morphodynamics are used to aid in the study of these processes. A number of depth-averaged two-dimensional models are available to simulate morphologic adjustment of both bed and banks. Unfortunately, these models use overly simplified conceptual models of riverbank erosion, are limited by inflexible structured mesh systems, or are unable to accurately account for the flow and sediment transport adjacent to streambanks of arbitrary geometry. A new, nonlinear model is introduced that resolves these limitations. The model combines the river morphodynamics computer models TELEMAC-2D and SISYPHE of the open source TELEMAC-MASCARET suite of solvers with the bank erosion modules of the CONCEPTS channel evolution computer model. The performance of the new model is evaluated for meander-planform initiation and development. The most important findings are: (1) the model is able to simulate a much greater variety and complexity in meander wavelengths; (2) simulated meander development agrees closely with the unified bar-bend theory of Tubino and Seminara (1990); and (3) the rate of meander planform adjustment is greatly reduced if the wavelength of alternate bars is similar to that of meanders.
... We used a hydromorphodynamic model to simulate bed load transport during the selected August 2014 flood event based on the Telemac hydroinformatic system, release 6.2 [Hervouet and Bates, 2000]. This system dynamically couples a three-dimensional hydrodynamic model (Telemac-3-D) and a one-dimensional sediment transport/morphodynamic model (Sysiphe) with an identical time step. ...
The characterization of bedload transport in rivers is critical for the fundamental understanding and management of fluvial systems. Bedload monitoring based on seismological observations has recently emerged as a viable non-invasive measurement technique. However, applications of this new approach have been hitherto restricted to the case of sediment transport in steep mountain rivers. Here, we further develop and evaluate the approach for a lower-gradient gravel-bed stream in a rural catchment using seismic observations, in-situ hydroacoustic measurements of bedload motion (impact-plate-type device), and 3D hydro-morphodynamic modeling. The results of this joint analysis of seismic measurements, hydroacoustic records and sediment transport simulations show that the seismic monitoring technique for bedload transport characterization is applicable for a broader range of river systems than previously investigated.
... The two-dimension hydraulic model in the OIN area is build with TELEMAC-2D module integrated into the TELEMAC modelling system. TELEMAC-2D is used to simulate free-surface flows in two dimensions of horizontal space [4,5]. At each point of the mesh, the program calculates the depth of water and the two velocity components. ...
Grand Paris is a new global plan for the Paris metropolitan region; it has lead to
a new transportation master plan and to development of several areas around
Paris. Our case study is the project of national interest (Opération d’Intérêt
National) by EPA ORSA (public institution of town planning Orly-Rungis-
Upstream Seine river), located in the south-east of Paris suburbs, including Seine
and Marne rivers. The urban sustainable development of this area should be
finished in 2050, its aim is to \“live with the river” but at the same time increase
the resilience. We have created a 2D model (with TELEMAC 2D) of the EPA
ORSA territory, and run several urbanization scenarios for different stages of the
project (2011, 2018, 2025 and 2050) and ten flood events. The redevelopment of
the Seine Valley has to respect the French Water Act and then cause zero impact.
Also, we have built a 1D model (with HEC-RAS) to spread the water level and
discharge impact in the Seine Valley (upstream and downstream of the 2D area).
Through the \“Grandes Ardoines”, located in Vitry example, we can see that an
urban sustainable development without hydraulic impact is possible.
Keywords: TELEMAC 2D, resilience, floods, Paris, sustainable development,
hydraulic impact, town planning.
... ANSWERS [10] and SWATRER [13] models are the base of the LISEM model. During 1998-2000, as a common project between China and the Netherlands, erosion in loss conservational programs of China was measured based on this model and Hessel [55] published the conclusions. At the same time (1998-1999 duration), other regions of the world evaluated this model. ...
This chapter attempts have been made to present different types of models in the simulation of
flow and sediment transport in rivers. http://www.crcpress.com/product/isbn/9781466552463
... The numerical modeling process uses TELEMAC [Galland et al., 1991], developed by the National Hydraulics and Environment Laboratory of the Research and Development Directorate of the French Electricity Board in collaboration with other research institutes. TELEMAC contains in particular the TOMAWAC module [Benoit et al., 1996] for calculating the wave propagation and the TELEMAC 2D module [Hervouet and Bates, 2000] for calculating the hydrodynamics. The TELEMAC-2D code solves depth-averaged free surface flow equations as derived first by Barré de Saint-Venant in 1871. ...
The paper presents a risk assessment methodology for operational limit states of submarine outfall projects that considers: the environmental legislative framework, the climate agents acting on the coastline and prediction of the plume long-term behaviour near the coastline. The probability of operational failure or stoppage is assessed enabling decision on project design alternatives.
... These equations are approximated on an irregular or unstructured mesh using the finite element method [32]. TELEMAC-2D has been validated for many analytic, experimental and real-world cases [33,32]. ...
... In the present study, the open source code TELEMAC 6.1 was used (Hervouet and Bates, 2000), which includes a depth-averaged version (TELEMAC-2D) for tidal modelling, as well as a model for simulation of wave condition (TOMAWAC), and consequent transport of sediment (SISYPHE). The three modules were each applied to the three estuaries and the adjacent 40 km offshore zone of Liverpool Bay as shown in Fig. 1. ...
In order to understand the influences of tide, waves and sediment sizes on the sand exchange between an estuary and the adjacent coastal region, three estuaries around North West England were chosen for detailed study using a numerical morphological model system, TELEMAC (Hervouet and Bates, 2000). The numerical model was calibrated against available field measurements for both hydrodynamics and sediment transport. Simulations on sediment transport under a representative combined waves and tidal condition were carried out. Comparisons of the model results across the three different estuaries concentrate on effects from seabed bathymetry, hydrodynamics and sediment sizes under the complex tide and wave interactions. It is clear that the dominant hydrodynamic processes of an estuary are influenced by the tidal asymmetry, wave-driven currents and wave-induced stirring effects, which are all affected by the local seabed bathymetry given the same input tide and waves. Generally, it is found that the net sediment transport direction at the estuary mouth depends on the relative strength of landwards transport in the shallow water depths due to tidal asymmetry and seawards transport within the estuary's deep channels. In addition, the overall sediment flux direction is largely dictated by local and surrounding sediment sizes.
... Following the recommendations proposed by Hardy et al. (2000) and Benjankar and Yager (2012), we made use of a modelling system able to carry out unsteady simulations, to take account of advection and diffusion processes, feedback processes between topography and hydrodynamic variables, and to integrate input suspended-sediment concentration as boundary conditions. According to these requirements, the model that has been set up is based on the open source Telemac hydro-informatic system (release 6.2) (Hervouet and Bates, 2000). The latter allows for dynamically coupling a 2D-shallow water hydrodynamic model -Telemac-2D -and a sediment transport model -Sisyphe. ...
Fine sediments represent an important vector of pollutant diffusion in rivers. When deposited in floodplains and riverbeds they can be responsible for soil pollution. In this context, this paper proposes a hydro-morphodynamic modelling exercise aiming at predicting transport and diffusion of fine sediments and dissolved pollutants. The model is based upon the Telemac hydro-informatic system (dynamical coupling Telemac-2D-Sysiphe). As empirical and semi-empirical parameters need to be calibrated for such a modelling exercise, a sensitivity analysis is proposed. In parallel to the modelling exercise, an extensive hydrological/geochemical database has been set up during two flood events. The main sensitive parameters were found to be the hydraulic friction coefficient and the sediment particle settling velocity in water. Using the two monitored hydrological events as calibration and validation, it was found that the model is able to satisfyingly predict suspended sediment and dissolve pollutant transport in the river channel. In addition, a qualitative comparison between simulated sediment deposition in the floodplain and a soil contamination map shows that the preferential zones for deposition identified by the model are realistic.
... In these studies field observations (e.g. from wave rider buoys and acoustic Doppler current profilers, ADCPs), regional ocean models, and local models, e.g. SWAN [2], MIKE21 [3], and TELEMAC [4] will be used and guidance on site modelling will be developed. ...
EquiMar (Equitable Testing and Evaluation of Marine Energy Extraction Devices in terms of Performance, Cost and Environmental Impact) is one of the first round of energy projects under the European Commissions 7th Framework Programme (FP7). The three year EquiMar project aims to deliver a suite of protocols for the evaluation of both wave and tidal converters, harmonizing testing and evaluation procedures across the wide range of available devices, accelerating adoption through technology matching and improving the understanding of both environmental and economic impacts associated with the deployment of devices. The EquiMar protocols will cover site selection, initial design, scaling up of designs, the deployment of arrays and environmental impact assessment as well as economic issues. EquiMar will build on existing protocols, e.g. UK DTI Marine Renewables Development Fund (MRDF) protocols for wave and tidal energy, and engage with international standards setting activities, e.g. IEC TC114.
... The model platform used here is ESTEL-2D, the subsurface flow component of the TELEMAC modelling system (Hervouet and Bates, 2000) which solves the Richards equation in saturated and unsaturated porous media with the finite element technique. The model has recently been used to study high resolution floodplain hydrological processes (Bates et al., 2000; Claxton et al., 2003; Cloke et al., 2003 Cloke et al., , 2006a Cloke et al., , 2006b). ...
When studying hydrological processes with a numerical model, global sensitivity analysis (GSA) is essential if one is to understand the impact of model parameters and model formulation on results. However, different definitions of sensitivity can lead to a difference in the ranking of importance of the different model factors. Here we combine a fuzzy performance function with different methods of calculating global sensitivity to perform a multi-method global sensitivity analysis (MMGSA). We use an application of a finite element subsurface flow model (ESTEL-2D) on a flood inundation event on a floodplain of the River Severn to illustrate this new methodology. We demonstrate the utility of the method for model understanding and show how the prediction of state variables, such as Darcian velocity vectors, can be affected by such a MMGSA. This paper is a first attempt to use GSA with a numerically intensive hydrological model. Copyright © 2007 John Wiley & Sons, Ltd.
... These equations are approximated on an irregular or unstructured mesh using the finite element method [32]. TELEMAC-2D has been validated for many analytic, experimental and real-world cases [33,32]. ...
Many models of river meander migration rely upon a simple formalism, whereby the eroding bank is cut back at a rate that is dictated by the flow, and the depositing bank then migrates passively in response, so as to maintain a constant bankfull channel width. Here a new model is presented, in which separate relations are developed for the migration of the eroding bank and the depositing bank. It is assumed that the eroding bank consists of a layer of fine-grained sediment that is cohesive and/or densely riddled with roots, underlain by a purely noncohesive layer of sand and/or gravel. Following erosion of the noncohesive layer, the cohesive layer fails in the form of slump blocks, which armor the noncohesive layer and thereby moderate the erosion rate. If the slump block material breaks down or is fluvially entrained, the protection it provides for the noncohesive layer diminishes and bank erosion is renewed. Renewed bank erosion, however, rejuvenates slump block armoring. At the depositing bank, it is assumed that all the sediment delivered to the edge of vegetation due to the transverse component of sediment transport is captured by encroaching vegetation, which is not removed by successive floods. Separate equations describing the migration of the eroding and depositing banks are tied to a standard morphodynamic formulation for the evolution of the flow and bed in the central region of the channel. In this model, the river evolves toward maintenance of roughly constant bankfull width as it migrates only to the extent that the eroding bank and depositing bank ‘talk’ to each other via the medium of the morphodynamics of the channel center region. The model allows for both (a) migration for which erosion widens the channel, forcing deposition at the opposite bank, and (b) migration for which deposition narrows the channel forcing erosion at the opposite bank. Copyright © 2010 John Wiley & Sons, Ltd.
... The TELEMAC Modelling System (Hervouet and Bates, 2000) is applied to the Dyfi Estuary and neighbouring coastline in Cardigan Bay, Wales. The coastal area is influenced by tides, rivers, waves and wave-induced currents. ...
Medium-term prediction of sediment transport and morphological behaviour in the coastal zone is becoming increasingly important as a result of human interference and changing environmental conditions. The interaction of waves and tides is shown to play a pivotal role in the net (annual) sediment transport and morphodynamics of the coastal zone. The Telemac Modelling System has been applied to the Dyfi Estuary and neighbouring coastline, mid Wales, to recreate the annual wave–current conditions and the resulting sediment fluxes. ‘Input reduction’ methods have been required to produce realistic schematisations of events in practical computation times. A field campaign carried out in 2006 provided data for validation of the flow module (Telemac-2D) and also observations to verify the patterns predicted by the wave module (Tomawac). To improve model accuracy refinements were implemented with regard to the sand transport formulation used in the sand transport module (Sisyphe). Here, a parameterisation of the results from the UWB 1DV sand transport ‘research’ model, for the conditions in the Dyfi Estuary, has been introduced, allowing Sisyphe to provide greater realism in the morphological predictions. The model predictions are presented along with a discussion of the success/failure and limitations of the modelling methods applied.
... Alternatively , 2D and 3D models make spatially distributed velocity (depth-averaged for 2D) and depth predictions. Many examples of public 2D hydrodynamic models now exist: FESWMS (Froehlich, 1989), RMA2 (Donnell et al., 2001), TELEMAC (Galland et al., 1991; Hervouet, 2000; Hervouet and Bates, 2000) and RIVER2D (Steffler and Blackburn, 2002). A code capable of modelling subcritical-supercritical transitions, wetting and drying and steady and unsteady flows is suggested. ...
Altered sediment and flow regimes in regulated rivers limit available spawning habitat for many fishes, especially salmonids. Mitigation efforts include spawning habitat rehabilitation and dam-removal, but often neglect conceptual or predictive models of hydrogeomorphic and ecological processes. Complete restoration of processes necessary for maintaining spawning habitat is often unrealistic in regulated rivers. However, we present a framework for spawning habitat rehabilitation based on the premise that certain ecologic functions and geomorphic processes can be restored in a manner that facilitates testing of underlying scientific theories. SHIRA (Spawning Habitat Integrated RehabilitationApproach) provides a science-based, systematic framework for reach-scale rehabilitation of salmonid spawning habitat in regulated rivers. This approach is driven by a mix of field data, conceptual models and numerical models to provide predictive and explanatory insight into the rehabilitation process. Conceptual models are advocated for developing multiple design scenarios and explicit hypotheses about hydrogeomorphic processes and ecologic functions provided by said designs. Hydrodynamic, habitat suitability and sediment entrainment models that test the potential validity of design hypotheses prior to construction are reviewed. It is presumed that the added insight would improve the outcome of rehabilitation projects and test underlying scientific theories against the rigors of real-world uncertainties.
The present study focuses on the sediment deposition and consequent dredging issues in Lower Ohio River at the Olmsted Locks and Dam area-River mile (RM)-964.4 during the ongoing in-the-wet construction methodology. The study reach is between Locks and Dam 53 (RM 962.6) at upstream, and RM 970 at downstream. One dimensional (1-D) HEC-RAS numerical modeling in conjunction with Arc-GIS was employed. Streamflow measurements, velocity, incoming sediment concentration, bed gradation, and annual hydrographic survey data acquired from public archives of USGS and USACE Louisville District were used as inputs. The model was subjected to the 1-D quasi-unsteady and completely unsteady sediment transport module, available in the latest HEC-RAS 5.0 Beta release. Calibration and validation of the hydrodynamic and sediment models were performed using measured water surface elevation, velocity, and sediment loads at measured sections. Post-model calibration and validation, deposition to excavated cross-sections for future dam shells at Olmsted was predicted, which warrants dredging. The study attempted to analyze the sediment transport trend with the focus on deposition at Olmsted Locks and Dam area using the sensitivity analysis approach of transport capacity functions. Moreover, the capability of 1-D HEC-RAS quasi-unsteady and completely unsteady models were assessed in prediction of sediment deposition in the construction area (dam shells excavation area). A temporal deposition prediction model was developed that can potentially replace the current ad-hoc approach used to determine the dredging schedule. Likewise, a representative environmental risk associated with sedimentation in the study area was examined. The model can potentially be used as a decision support tool to analyze the long term impact of sedimentation in the vicinity of Olmsted Locks and Dam if further updates on the river bathymetry, and specific field data are supplemented to the model. ii ACKNOWLEDGEMENTS
The European Union (EU) project PROMINENT - Promoting Innovation in the Inland Waterways Transport (IWT) Sector - which was launched in May 2015, is a multiannual research and innovationi programme for inland navigation, funded by the Horizon 2020 programme of the European Union. Running until April 2018, and involving a number of important stakeholders of the IWT sector of the EU, the project focusses on:
• massive transition towards efficient and clean vessels by developing cost-effective solutions applicable to 70 % of the EU fleet and reduction of the corresponding implementation costs by 30 %;
• certification and monitoring of emission performance and development of innovative regimes;
• harmonisation and modernisation of professional qualifications and the stimulation of the further integration of IWT into sustainable transport chains.
Building upon the identification of the most promising greening technologies and the technical developments carried out in the project, several pilots were set up and started, delivering a great number of interesting results of significance to the IWT sector.
Based on the validated findings from amongst the research and the pilots, this report contains the policy conclusions, recommendations and roadmap. This is based on the evaluations and assessments for the various fields of the PROMINENT innovations. The goal is to prepare for mass implementation of the innovations that serve the overall aim of PROMINENT in terms of market reach and cost reductions.
Zur Erledigung der fachwissenschaftlichen Aufgaben in den Referaten Ästuarsysteme I und II werden
maßgeschneiderte IT-gestützte Methoden für die Bereiche Datenaufbereitung, Simulation (Hydrodynamik, Transport von gelösten und suspendierten Stoffen, Morphodynamik, Seegang), Analyse und Visualisierung benötigt.
Die IT-gestützten Methoden werden in der Softwaresammlung PROGHOME (PH) zusammengefasst. Hierbei wird der Code in Modulen, Paketen, externen Schnittstellen und Anwendungen strukturiert aufbereitet. Alle Komponenten werden kontinuierlich gepflegt und weiterentwickelt. Bei der Entwicklung wird Fortran
und teilweise MATLAB verwendet.
Die Softwaresammlung PH hat maßgeblich zur erfolgreichen Einführung und routinemäßigen Verwendung
numerischer Methoden in den küstenwasserbaulich ausgerichteten Referaten der BAW beitragen. Mit
Unterstützung der in PH vorhanden Methoden konnten im Laufe der Jahre 200 Gutachten, u. a. für mehrere Planfeststellungsverfahren an Ems, Jade-Weser, Elbe sowie im Nord- und Ostseeraum, erfolgreich abgeschlossen werden. Ca. 30 Mitarbeiter nutzen PH bei ihrer täglichen Arbeit.
Die Entwicklung der in PH abgelegten Software ist ein in die Referate Ästuarsysteme I und II eingebetteter
strukturierter Prozess. Sie steht in ständigem Bezug zu laufenden und anstehenden Aufgaben. Damit ist PH
Teil der Wissensallmende der BAW.
In the scope to create efficient nature like fish ramps using large-scale roughness elements, the present study is an audit of modelling such complex 3D free surface flows using an industrial 2D code solving shallow water equations. Validation procedure is based upon the comparison between numerous experimental measurements and numerical runs around large-scale roughness patterns disposed on the flume bottom in order to determine what 2D reliable numerical results can be expected. In this paper, we focused on cases of unsubmerged obstacles. The results demonstrate that 2D shallow water modelling using an industrial code such as TELEMAC-2D can be a convenient way for the hydraulic engineer to help design a nature-like fishway. This article emphasizes the limitations due to 2D depth integration of velocities and turbulence modelling and gives the domain of validity of the method.
In this study, the main object is to investigate the performance of a few new physics-based process models by implementation into a numerical model for the simulation of the flow and morphodynamics in the Western Scheldt estuary. In order to deal with the complexity within the research domain, and improve the prediction accuracy, a 2D depth-averaged model has been set up as realistic as possible, i.e. including two-way hydrodynamic-sediment transport coupling, mixed sand–mud sediment transport (bedload transport as well as suspended load in the water column) and a dynamic non-uniform bed composition. A newly developed bottom friction law, based on a generalised mixing-length (GML) theory, is implemented, with which the new bed shear stress closure is constructed as the superposition of the turbulent and the laminar contribution. It allows the simulation of all turbulence conditions (fully developed turbulence, from hydraulic rough to hydraulic smooth, transient and laminar), and the drying and wetting of intertidal flats can now be modelled without specifying an inundation threshold. The benefit is that intertidal morphodynamics can now be modelled with great detail for the first time. Erosion and deposition in these areas can now be estimated with much higher accuracy, as well as their contribution to the overall net fluxes. Furthermore, Krone’s deposition law has been adapted to sand–mud mixtures, and the critical stresses for deposition are computed from suspension capacity theory, instead of being tuned. The model has been calibrated and results show considerable differences in sediment fluxes, compared to a traditional approach and the analysis also reveals that the concentration effects play a very important role. The new bottom friction law with concentration effects can considerably alter the total sediment flux in the estuary not only in terms of magnitude but also in terms of erosion and deposition patterns.
Resumo Neste estudo apresenta-se uma metodologia de avaliação de riscos para estados limites operativos no projecto de emissários submarinos que considera: a natureza intrínseca da estrutura, a legislação ambiental Europeia em vigor, os agentes climáticos característicos da zona costeira e a previsão do comportamento da pluma a longo-prazo. Pretende-se ainda identificar alguns padrões principais do comportamento da pluma e a sua relação com os agentes forçadores locais: vento e maré. Esses padrões são obtidos para a região de Albufeira, onde se encontra o emissário de Vale de Faro, utilizando o método das funções ortogonais empíricas. A probabilidade de falha operativa ou paragem é considerada no dimensionamento probabilístico da estrutura. Com o presente estudo pretende-se estabelecer uma metodologia consistente para a optimização e gestão de riscos no projecto de emissários submarinos com base nas Recomendações Espanholas para Estruturas Marítimas, ROM, actualmente de aplicação essencialmente a portos e estruturas costeiras (Puertos del Estado, 2002). Esta metodologia permite avaliar a segurança e operatividade de emissários submarinos e será parte integrante da ferramenta, em desenvolvimento, para a optimização e gestão de riscos nos projectos de emissários submarinos.
This paper presents details of finite volume and finite element numerical models based on unstructured triangular meshes that are used to solve the two-dimensional nonlinear shallow water equations (SWEs). The finite volume scheme uses Roe's approximate Riemann solver to evaluate the convection terms. Second order accuracy is achieved by means of the MUSCL approach with MinMod and VanAlbada limiters. The finite element model utilizes the Lax–Wendroff two-step scheme, which is second-order in space and time. The models are validated and their relative performance compared for several benchmark problems, including a hydraulic jump, and flows in converging and converging–diverging channels.
The final publication is available at link.springer.com http://link.springer.com/article/10.1007%2Fs10452-004-8058-z#
Intertidal sedimentary environments are complex systems governed by interactions between physical, chemical and biological processes and parameters. Tidally induced flow and wave action are known to be an integral driving force behind the erosion, transport, deposition and consolidation cycle (ETDC) of intertidal sediments. Whilst considerable advances have been made in understanding both the physical and biological processes and their interactions in these systems, it is clear that there are gaps in our understanding. One factor that has been largely ignored to date is that of rain. Visual observations in the field and associated data indicated that rain showers during low tide are correlated with a reduction in the erosion threshold of intertidal cohesive sediments. This paper presents preliminary field and laboratory data showing the importance of rain in reducing the erosion threshold of cohesive intertidal sediments. The implications for our knowledge of, and modelling of the ETDC cycle of cohesive intertidal sediments are discussed.
Linear and nonlinear behavior of large-scale underwater bedform patterns like sandbanks are studied using linear stability analysis and numerical modeling. The model is based on depth-integrated hydrodynamics equations with a quadratic bottom friction law and a bed load sediment transport model including a bottom slope effect. First, the linear stability analysis of a flat erodible bottom subject to a steady current is performed. The direction of the most amplified bedform is controlled by the current, whereas its wavelength is selected by the gravity driven sediment flow. The instability proved to be due to the velocity component parallel to the mean flow, whereas the transverse velocity and the bottom slope effect are damping processes. The growth rate is then related to the spatial phase-lag between flow velocity and bathymetry. In order to validate the numerical model in this linear regime, the growth rate and the phase celerity of an infinitesimal bottom perturbation are computed as a function of its wavevector. A good agreement with linear stability results is found. Second, using the property that the growth rates for block-function and steady current are the same, the nonlinear behavior of the instability is investigated for a simple tidal current. The saturation height of the theoretically most amplified mode is estimated using the numerical model. The analysis of the sediment fluxes gradients shows that the saturation is mostly due to the hydrodynamic processes, although the saturation height slightly depends on the value of the bottom slope effect coefficient. Third, a Landau equation, whose coefficients are computed from the previous results, is used to predict the temporal evolution of the bedform amplitude from the initial infinitesimal perturbation to the saturation. A comparison with the
characteristics of continental shelf sandbanks shows that the model gives a reasonable
estimation of the temporal dynamics of these large-scale bedforms. However, the saturation height seems to be slightly overestimated. The limitations of the method are also
discussed.
A one month field campaign featuring two spring–neap tide cycles and three strong storms has been performed in a mobile dune area located in the central part of the Dover Strait. These dunes are known to move in a complex manner as their migration direction varies in space and time (Le Bot and co-workers, 2000, 2001, 2004). In order to gain some insights into the dune motion processes we present an analysis of the spatio-temporal variability of currents in the area emphasizing the relative influence of tides and storms. A total of eight different hydro-meteorological regimes have been distinguished during the experiment duration. The analysis of the currents measurements at five locations in the area shows that the eight hydro-meteorological regimes induce very different current responses at the bottom. The residual tidal currents exhibit a significant spatial variability both in direction and in intensity. A numerical model of tidal currents over the Dover Strait confirms the strong spatio-temporal variability of the residual tidal currents featuring three singular points. Amongst them, a saddle point is located just south of the I-dune at the convergence of opposite direction residual tidal currents. The wind-induced currents are almost uniform in space, their intensity and direction however strongly depends on the wind regime and thus on time. The mean total current feature a spatial pattern which can be tidal of wind-induced currents dominated, or either in balance, depending on the regime considered. At the PERMOD campaign time scale, the total current is dominated by the residual tidal current. These results proved to give valuable insights to explain the complex dynamics of dune motion observed in this area by Le Bot and co-workers (2000, 2001, 2004) at short and long time scales.
Increasing demands on water supplies, along with concerns about non-point source pollution, and water quality-based ecological factors all point to the need for observing stream flow perturbations and pollutant discharges at higher resolution than has been practical until now. This work presents a rapidly deployable Networked Infomechanical System (NIMS RD) technology for observing spatiotemporal variability in hydraulic and chemical properties across stream channels. NIMS RD is comprised of two supporting towers and a suspension cable delivering power and Internet connectivity for controlling and actuating the tram-like NIMS unit. The NIMS unit is capable of raising and lowering a payload of sensors, allowing a preprogrammed or data-actuated adaptive scan to be completed across a stream channel. In this paper, NIMS RD is demonstrated in two relevant cases: (1) elucidating spatiotemporal variations in nutrients and other biologically significant stream constituents in Medea Creek, a small urban stream in Southern California; and (2) using high-resolution synoptic sampling of steady velocity and salinity distributions across the San Joaquin River in Central California to provide quantitative salt load estimates. For Medea Creek, temperature and specific conductivity (SC) exhibited varying cross-sectional patterns throughout each of three 24 hour scans carried out over three summer months. Both temperature and SC displayed repeating sinusoidal diel fluctuations independent of the spatial variation. For each of the months the cross-sectional variation was less during the late nighttime and morning hours than during the afternoon and early nighttime hours. For the San Joaquin River, high-resolution velocity distributions from NIMS RD were successfully reproduced in separate deployments and quantitatively matched stage-based volumetric flow rates at the site. The product of the velocity and associated SC distributions yielded total salt load estimates similar to previously reported values, but no basis for direct comparison was available.
The riparian zone is in intimate contact with the river and, as such, is a critical zone for understanding hydrological problems. This paper presents a general modelling methodology for the assessment of riparian hydrological processes. It is applicable to a wide range of riparian spaces and incorporates current expertise in numerical methods. A core part of the modelling methodology is the random walk particle method (RWPM). We develop an RWPM as part of the ESTEL2D subsurface flow model, test it against analytical solutions and apply it to the simulation of parcels of water as they move through the riparian zone. The modelling methodology provides a new opportunity to assess fundamental hydrological process issues such as the proportioning of pre-event and event water storm runoff, and reversals of flow in floodplains.
In recent years, the exploitation of marine aggregates is increasing. As an example, on the Belgian continental
shelf, one particular sandbank (the Kwinte Bank) is exploited extensively; this has led to the creation of a 5 m deep
depression along its central part. In the present contribution, the influence of these bathymetric changes, on erosion
and sedimentation patterns are studied, using numerical modelling, in order to obtain an initial impression of the
effect of such intense sand extraction on the stability of the sandbank. Different numerical models are utilised. Twodimensional
and three-dimensional hydrodynamic models have been used to derive currents, whilst third generation
wave models have been used to simulate the waves. Two different models are presented, which calculate the total
load sediment transport as a function of the local currents and waves. These models have been used to investigate the
erosional and depositional patterns. The use of two different sediment transport models has some advantages, since
the results of sediment transport models are still subject to some important uncertainties. The hydrodynamic model
results are validated using ADCP current data, confirming the good performance of the models. Likewise the wave
models provide good results, comparing their results with data from a buoy. The sediment transport model results
were compared to the residual transport patterns, derived from the asymmetry of dunes. The results obtained seem
to be in general agreement with these observations. The numerical models are used to simulate the response of the
sediment transport to extensive sand extraction from the sandbank. One ‘worst-case’ scenario and two more realistic
scenarios were simulated, whilst the effect of these bathymetric changes on sediment transport was studied. The
results show that the intense sand extraction does not seem to influence extensively the stability of the sandbank, but
that, as a consequence, there is less erosion and deposition. The model results show, for all of the scenarios, a small
amount of deposition on the top of the sandbank; this could be an indication of a regeneration mechanism. A trench,
created perpendicular to the crest of the sandbank, could be slowly refilled again. The time-scale of this regeneration
and the influence of storms remain uncertain. Although the main emphasis of the paper relates to tidal forcing, a
brief discussion is included on the influence of wave action, on sediment transport.
We introduce in this paper two original Mixed methods for the numerical resolution of the (stationary) Primitive Equations
(PE) of the Ocean. The PE govern the behavior of oceanic flows in shallow domains for large time scales. We use a reduced
formulation (Lions et al. [28]) involving horizontal velocities and surface pressures. By using bubble functions constructed
ad-hoc, we are able to define two stable Mixed Methods requiring a low number of degrees of freedom. The first one is based on the
addition of bubbles of reduced support to velocities elementwise. The second one makes use of conic bubbles of extended support along the vertical coordinate. The latter constitutes a genuine mini-element for the PE, e.g., it requires the least number of extra degrees of freedom to stabilize piecewise linear hydrostatic pressures.
Both methods verify a specific inf-sup condition and provide stability and convergence. Finally, we compare several numerical
features of the proposed pairs in the context of other FE methods found in the literature.
The effects of simulated rain on the erosion threshold and biogeochemical properties of cores of muddy intertidal sediments were measured. Rain was simulated with a trailer-mounted device that produced rain with an intensity and drop size similar to that of natural rain. Erosion thresholds were measured with a cohesive strength meter (CSM) and sediment samples for analysis of the biogeochemical properties of the sediment were collected using the cryogenic contact-core technique. Rain caused significant disruption of the sediment surface, often resulting in significantly lower erosion thresholds and increased relative erosion rates. The removal of unconsolidated surface sediments and the revealing of deeper more consolidated sediments, however, caused an increase in the measured erosion threshold and a reduction in erosion rate in some treatments. The biogeochemical properties of the sediment were significantly altered by even a short duration of rain (5 min). Bio-dependent properties such as the amount of chlorophyll a and carbohydrates were generally decreased by rain. The presence of a visible biofilm did not significantly mediate the effects of rain on erosion thresholds, in contrast to their ability to significantly reduce erosion by tidal flows.
ResearchGate has not been able to resolve any references for this publication.