165 results on '"Roelvink, Dano"'
Search Results
152. A Simple Method to Predict Long-Term Morphological Changes
- Author
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Roelvink, Dano, primary, Boutmy, Alain, additional, and Stam, Jean-Marie, additional
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- 1999
- Full Text
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153. Bed composition generation for morphodynamic modeling: case study of San Pablo Bay in California, USA.
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Wegen, Mick, Dastgheib, Ali, Jaffe, Bruce, and Roelvink, Dano
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ESTUARINE sediments ,GEOMORPHOLOGY ,SENSITIVITY analysis ,SEDIMENT transport ,SAND ,BATHYMETRIC maps - Abstract
pplications of process-based morphodynamic models are often constrained by limited availability of data on bed composition, which may have a considerable impact on the modeled morphodynamic development. One may even distinguish a period of 'morphodynamic spin-up' in which the model generates the bed level according to some ill-defined initial bed composition rather than describing the realistic behavior of the system. The present paper proposes a methodology to generate bed composition of multiple sand and/or mud fractions that can act as the initial condition for the process-based numerical model Delft3D. The bed composition generation (BCG) run does not include bed level changes, but does permit the redistribution of multiple sediment fractions over the modeled domain. The model applies the concept of an active layer that may differ in sediment composition above an underlayer with fixed composition. In the case of a BCG run, the bed level is kept constant, whereas the bed composition can change. The approach is applied to San Pablo Bay in California, USA. Model results show that the BCG run reallocates sand and mud fractions over the model domain. Initially, a major sediment reallocation takes place, but development rates decrease in the longer term. Runs that take the outcome of a BCG run as a starting point lead to more gradual morphodynamic development. Sensitivity analysis shows the impact of variations in the morphological factor, the active layer thickness, and wind waves. An important but difficult to characterize criterion for a successful application of a BCG run is that it should not lead to a bed composition that fixes the bed so that it dominates the 'natural' morphodynamic development of the system. Future research will focus on a decadal morphodynamic hindcast and comparison with measured bathymetries in San Pablo Bay so that the proposed methodology can be tested and optimized. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
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154. Large-Scale Coastal Evolution Concept
- Author
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Stive, Marcel J. F., primary, Roelvink, Dano (J.) A., additional, and de Vriend, Huib J., additional
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- 1991
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155. Climate-change impact assessment for inlet-interrupted coastlines
- Author
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Ranasinghe, Roshanka, Duong, Trang Minh, Uhlenbrook, Stefan, Roelvink, Dano, and Stive, Marcel
- Abstract
Climate-change (CC)-driven sea-level rise (SLR) will result in coastline retreat due to landward movement of the coastal profile (that is, the Bruun effect). Coastline change adjacent to commonly found tidal inlets will be influenced not only by the Bruun effect, but also by SLR-driven basin infilling and CC-driven variations in rainfall/runoff. However, as a model that accounts for all of the above-mentioned processes has been lacking so far, most coastal CC impact studies until now have considered only the Bruun effect. Here, we present a scale-aggregated model capable of providing rapid assessments of coastline change adjacent to small inlet-estuary/lagoon systems due to the combined effect of CC-driven SLR and variations in rainfall/runoff. Model applications to four representative systems show that the Bruun effect represents only 25–50% of total potential coastline change, and underline the significance of coastline change due to SLR-driven basin infilling and CC-driven variations in rainfall/runoff.
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- 2013
- Full Text
- View/download PDF
156. 3D modelling of nearshore coastal morphodynamics
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Bakhtyar, Roham, Dastgheib, Ali, Roelvink, Dano, and Barry, David Andrew
- Abstract
Coastal 3D nearshore processes were considered with an emphasis on the effects of oceanic forcing and beach characteristics on sediment transport in both cross- and alongshore directions, as well as on foreshore bathymetry changes. In our numerical experiments, we combined the FLOW module of the Delft3D model with the WAVE solver of Xbeach models. k-ε turbulence closure was used to resolve the three-dimensional Navier-Stokes equations for incompressible flow and the beach morphology. The sediment transport module simulates both bedload and suspended load transport of non-cohesive sediments. A series of numerical experiments was performed for a range of control parameters. For each case, the general morphological response was determined in the shore-normal and shore-parallel directions. The simulations confirmed that the sole wave forcing is sufficient to drive a sediment circulation pattern that results in bar and berm formation. The wave characteristics have a considerable effect on the cumulative erosion/deposition, cross-shore distribution of longshore sediment transport, and the sediment transport rate across and along the beach face. For the same oceanic forcing, beach morphology exhibits different erosive characteristics depending on grain size. Fine beach sands were transported offshore, whereas coarse sands moved onshore-wards. Sediment movement increases with wave energy, which was shown to be the most dominant factor controlling the beach face shape. In the surf zone, the sediment transport rate increases towards the shore until the wave collapses whereas in the swash zone it decreases. The present model is able to reproduce complicated flow and sediment transport processes and estimation of beach face dynamics.
157. Influence of beach grain size and bed slope on nearshore hydro- and morpho-dynamics
- Author
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Bakhtyar, Roham, Dastgheib, Ali, Barry, David Andrew, and Roelvink, Dano
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Two major parameters that determine the beach type are sediment grain size and beach slope. Intermediate beaches normally have steep slopes and are associated with coarse-grained sands and narrow surf zones, while dissipative beaches generally have mild slopes and are related to fine sands and wider surf zones. In numerical experiments, the Delft3D and Xbeach models were combined to resolve the 3D Navier-Stokes equations for incompressible flow and beach morphology. The sediment transport module supports both bed-load and suspended load transport of non-cohesive sediments. Numerical simulations were run for different hydrodynamic conditions, but with a focus on different beach slopes and grain sizes, and considering hydrodynamic processes, sediment transport in cross- and alongshore directions, as well as foreshore bathymetry changes. Larger grain sizes tend to generate more complex nearshore hydrodynamic patterns. The transformation of incoming waves as they reach shallow water occurs closer the shoreline for steeper profiles. Consistently, the peaks in eddy viscosity, turbulence dissipation rate (TDR), turbulent kinetic energy (TKE) and wave set-up are shifted onshore for steeper slopes. High values of eddy viscosity, TKE and wave set-up are spread offshore for coarser grain sizes. The TDR is an order of magnitude smaller for the coarsest grains compared with other cases. The numerical results showed that TKE, sediment concentrations and sediment transport rate are greater on steep beaches than on mildly sloped beaches. The beach morphology exhibits different erosive characteristics depending on grain size (e.g., foreshore profile evolution is erosive and accretionary on fine and coarse sand beaches, respectively). The results confirmed that wave energy, beach grain size and bed slope are the main factors influencing sediment transport and beach morphodynamics.
158. Development of a 3D wave-current interaction formulation.
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Nguyen Tan Duoc and Roelvink, Dano
- Subjects
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WAVE-current interaction - Published
- 2018
159. MICORE: DUNE EROSION AND OVERWASH MODEL VALIDATION WITH DATA FROM NINE EUROPEAN FIELD SITES (AND BEYOND).
- Author
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Van Dongeren, Ap, Benavente, Javier, Balouin, Yann, Ciavola, Paolo, Taborda, Rui, Furmańczyk, Kazimierz, Haerens, Piet, Roelvink, Dano, Trifonova, Ekatarina, and Williams, Jon
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COASTAL changes ,STORMS ,SHORE protection ,BEACH erosion - Published
- 2009
160. Dynamic Modelling of Rip Currents for Swimmer Safety on a Wind-Sea–Dominated Mesotidal Beach
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Sembiring, Leo, van Dongeren, Ap, Winter, Gundula, and Roelvink, Dano
- Published
- 2015
- Full Text
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161. Evolution of the Bengal Delta and Its Prevailing Processes
- Author
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Akter, Jakia, Sarker, Maminul Haque, Popescu, Ioana, and Roelvink, Dano
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- 2015
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162. Modelling and analysis on high sediment concentration layer of fine sediments under wave-dominated conditions.
- Author
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Lu, Yongjun, Zuo, Liqin, Wang, Hao, and Roelvink, Dano
- Subjects
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COMPOSITION of marine sediments , *WAVE analysis , *SEDIMENT transport , *SILT , *SAND , *MATHEMATICAL models - Abstract
Abstract Experiments and field observations have revealed that when silt and very fine sand are subject to oscillatory wave motion, a high shear flow layer and a high concentration layer (HCL) exist near the bottom. The behavior of the HCL is still under researched. Firstly, an intra-wave process based 1DV model was established for fine sediment transport under the combined action of waves and currents. Some key processes that were included in the model are represented through approaches for different bed forms (rippled bed and 'flat bed'), hindered settling, stratification, reference concentration and critical shear stress. A number of experimental datasets were collected to verify the model, which shows that the model is able to properly simulate the flow and sediment dynamics. Secondly, sensitivity analyses were carried out on some factors which would impact the suspended sediment concentration (SSC) profile of the HCL by the 1DV model, such as bed forms, flow dynamics, stratification effects, mobile bed effects and hindered settling. Results show that bed forms play a significant role in the HCL and determination of the shape of the concentration profile. When a current is imposed, the SSC profiles become smoother; however, sediment concentration in the lower HCL is still dominated by the wave motions. For finer sediment, the stratification effects and the mobile bed effects strongly impact the HCL. In conclusion, this paper provides a tool for the study of the HCL and an evaluation of several impact factors on the HCL. Highlights • An intra-wave process based 1DV model was established for silty sediment movement under the combined action of waves and currents. • Important factors impacting the high concentration layer (HCL) are bed forms, flow dynamics, stratification and mobile bed effects. • Bed forms play a significant role in the HCL and determination of the shape of the concentration profile. • For fine sediment, the stratification effects and the mobile bed effects strongly impact the HCL. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
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163. Water circulation pattern in the main channels of Ria Formosa based on tidal analysis
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Permata, Della, Duarte, Duarte, and Roelvink, Dano
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Hidrodinâmica ,Hidrologia ,Marés ,Algarve - Ria Formosa ,Ecologia - Abstract
Dissertação de mest., Eco-Hidrologia, Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2012 Ria Formosa lagoon, Southern coast of Portugal is considered as a very dynamic system. Current and water level data measurements of tidal dynamic in the main channels of Ria Formosa lagoon had been carried to figure out the hydrodynamic water circulation patterns. The aims of this study in general is to generate a recent hydrodynamic water circulation patterns based on tidal analysis, with the output of tidal dynamic characteristic (tidal propagation, tidal asymmetry and tidal distortion, energy flux and dissipation, water level and velocity longitudinal gradients, phase lag, tidal prisms, water discharge, etc) and residence time, which are used to identify the most suitable areas for seashell to grow. Several time series of water level and longitudinal component of velocity variations data during completed tidal cicles in the 12 station points of the main channel in Ria Formosa were analyzed using harmonic analysis methods and obtained the average errors of 7.5 % velocity root mean square and 6.75% elevation root mean square, respectively. The tidal analysis results when projected in GIS platform enabled to highlight water circulation patterns in the main channel of Ria Formosa and showed the significance role of Faro-Olhão inlet and Armona inlet in term of energy, volume, and discharge, and less significance role of Sao Luis inlet. The spatial variability of residence time in each stations was obtained and showed that in the west and middle regions of Ria Formosa, a good water exchange were indicated, while in east region, a high residence time magnitude was discovered especially in the inner part of east region with 6.7 days of residence time. This finding result was combined with the average current velocity and maximum flood current and found that Nave Pegos, Culatra, Cações, and Bela Romão stations and adjacent areas are the most suitable area for seashell to grow. The comparison study between inlet tidal cycle volume and geometric volume calculation was carried out and showed that volume difference represent in average a -38 cm of water level height difference estimation for all lagoon. The future development of this work will allow introducing a quality level of understanding of the system in Ria Formosa and can give contribution for the fisherman as a preliminary step to find the suitable place for doing seashell aquaculture/ harvesting. Hence, from the Eco-hydrological perspective, the result of this study could be used for the decision maker as a management tool that related to anthropogenic activities such as dredging activity, inlet opening, and other activities that can give impact to the biota life in Ria Formosa. O sistema lagunar da Ria Formosa localiza-se na zona costeira Sul de Portugal. Este trabalho teve por principal objectivo estudar os principais padrões de circulação da água nos canais principais, tendo por base leituras de velocidade da corrente e da variação da superfície livre, medidos em vários locais na Ria Formosa. Pretendeu igualmente estudar a propagação e a dissipação de energia da maré, os gradientes longitudinais referentes à variação da superfície livre e à velocidade da corrente, os atrasos da maré em diferentes locais, os prismas de maré, os volumes de água em circulação nos canais principais, os tempos de residência e as potenciais áreas para um melhor crescimento de bivalves tendo por base vários parâmetros hidrodinâmicos. Para o efeito foram medidas série de dados referentes à variação da superfície livre e variação da velocidade na coluna de água, ao longo de ciclos de maré, em 12 estações distribuídas na Ria Formosa, que foram submetidas a uma análise harmónica. Para a componente vertical da maré foram obtidos erros RMS médios de 6.75% e para a componente horizontal de 6.75%. Os resultados obtidos desta análise, quando projectados num sistema SIG permitiram realçar a importância das barras de Faro-Olhão e da Armona na circulação hidrodinâmica deste sistema lagunar em termos energéticos, volume e caudais, bem como uma menor importância relativa por parte da barra de S. Luís. Quando analisados os tempos de residência nas várias estações em estudo, verificou-se que as regiões Central e Oeste da ria foram caracterizadas por uma boa troca de água, enquanto nos sectores mais interiores da região Este por tempos de residência elevados de aproximadamente 6.7 dias. Estes resultados quando conciliados com as respectivas velocidades médias e velocidades máximas de enchente, permitiram definir as estações de Nave Pegos, Culatra, Cações e Bela Romão (e zonas adjacentes) com as mais indicadas para o crescimento de bivalves. Quando comparados os volumes referentes aos prismas de maré obtidos através das séries de dados maregráficos medidos nas barras em análise, com os prismas de maré geométricos obtidos pela plataforma GIS, constatou-se haver uma diferença entre eles que se materializou numa diferença media da altura da água na laguna da ordem dos -38cm. Este trabalho para além de contribuir para melhor conhecimento do funcionamento hidrodinâmico da Ria Formosa, e dar um contributo para as associações de mariscadores locais com estes resultados preliminares sobre as melhores localizações para os viveiros de marisco neste sistema lagunar, poderá permitir introduzir em trabalhos futuros outros parâmetros que ajudarão a definir as melhores áreas para a implementação deste viveiros. Os resultados obtidos neste trabalho no âmbito da Eco-hidrologia, poderão ser usados não só como uma ferramenta de decisão para as entidades locais, mas também dar informações primordiais para a gestão deste sistema costeiro no que diz respeito a actividades antropogénicas, tais como a gestão de trabalhos de dragagem, a abertura de novas barras, e outras actividades que possam ter impactes no Biota da Ria Formosa.
- Published
- 2013
164. Assimilation de données et inversion bathymétrique pour la modélisation de l'évolution des plages sableuses
- Author
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BIRRIEN, Florent, Castelle, Bruno, Bertin, Xavier, Cosme, Emmanuel, Marieu, Vincent, Lecroart, Pascal, Barthélémy, Eric, and Roelvink, Dano
- Subjects
Filtre de Kalman ,Télédétection ,Bathymétrie ,Modélisation hydro-morphodynamique ,Inversion bathymétrique ,Assimilation de données ,Imagerie vidéo
165. Morphodynamique littorale haute fréquence par imagerie vidéo
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ALMAR, Rafael, Bonneton, Philippe, Sénéchal, Nadia, Garlan, Thierry, Mulder, Thierry, Abadie, Stéphane, and Roelvink, Dano
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Littoral aquitain ,Célérité des vagues ,Ligne d'eau ,Impact des tempêtes ,Biscarrosse ,Structures sableuses périodiques ,Mécanisme d'auto-organisation ,Mécanismes d'interactions entre barres sableuses ,Truc Vert
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