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Sébastien Blaise Benjamin de Brye Anouk de Brauwere Eric Deleersnijder Eric J. M. Delhez Richard Comblen 《Ocean Dynamics》2010,60(3):535-554
At high Peclet number, the residence time exhibits a boundary layer adjacent to incoming open boundaries. In a Eulerian model,
not resolving this boundary layer can generate spurious oscillations that can propagate into the area of interest. However,
resolving this boundary layer would require an unacceptably high spatial resolution. Therefore, alternative methods are needed
in which no grid refinement is required to capture the key aspects of the physics of the residence time boundary layer. An
extended finite element method representation and a boundary layer parameterisation are presented and tested herein. It is
also explained how to preserve local consistency in reversed time simulations so as to avoid the generation of spurious residence
time extrema. Finally, the boundary layer parameterisation is applied to the computation of the residence time in the Scheldt
Estuary (Belgium/The Netherlands). This timescale is simulated by means of a depth-integrated, finite element, unstructured
mesh model, with a high space–time resolution. It is seen that the residence time temporal variations are mainly affected
by the semi-diurnal tides. However, the spring–neap variability also impacts the residence time, particularly in the sandbank
and shallow areas. Seasonal variability is also observed, which is induced by the fluctuations over the year of the upstream
flows. In general, the residence time is an increasing function of the distance to the mouth of the estuary. However, smaller-scale
fluctuations are also present: they are caused by local bathymetric features and their impact on the hydrodynamics. 相似文献
2.
Palaeoflood hydraulic modelling is essential for quantifying ‘millennial flood’ events not covered in the instrumental record. Palaeoflood modelling research has largely focused on one-dimensional analysis for geomorphologically stable fluvial settings because two-dimensional analysis for dynamic alluvial settings is time consuming and requires a detailed representation of the past landscape. In this study, we make the step to spatially continuous palaeoflood modelling for a large and dynamic lowland area. We applied advanced hydraulic model simulations (1D–2D coupled set-up in HEC-RAS with 950 channel sections and 108 × 103 floodplain grid cells) to quantify the extent and magnitude of past floods in the Lower Rhine river valley and upper delta. As input, we used a high-resolution terrain reconstruction (palaeo-DEM) of the area in early mediaeval times, complemented with hydraulic roughness values. After conducting a series of model runs with increasing discharge magnitudes at the upstream boundary, we compared the simulated flood water levels with an inventory of exceeded and non-exceeded elevations extracted from various geological, archaeological and historical sources. This comparison demonstrated a Lower Rhine millennial flood magnitude of approximately 14,000 m3/s for the Late Holocene period before late mediaeval times. This value exceeds the largest measured discharges in the instrumental record, but not the design discharges currently accounted for in flood risk management. 相似文献
3.
Bomers A. Aguilar Lopez J. P. Warmink J. J. Hulscher S. J. M. H. 《Natural Hazards》2018,94(1):493-493
Natural Hazards - The article was published Open Access under the Dutch Compact Agreement; however, due to an internal system error, previous HTML rendering of the article did not reflect this. 相似文献
4.
Origin and formation pathways of kerogen-like organic matter in recent sediments off the Danube delta (northwestern Black Sea) 总被引：1，自引：0，他引：1
Anouk Garcette-Lepecq Sylvie Derenne Claude Largeau Ioanna Bouloubassi Alain Saliot 《Organic Geochemistry》2000,31(12):204
The chemical structure, source(s), and formation pathway(s) of kerogen-like organic matter (KL) were investigated in recent sediments from the northwestern Black Sea, off the Danube delta. Three sections from a sediment core collected at the mouth of the Sulina branch of the delta, under an oxic water column, were examined: S0 (0–0.5 cm bsf), S10 (10–13 cm bsf), and S20 (20–25 cm bsf). The bulk geochemical features of these sediments (total organic carbon, organic C/N atomic ratio, δ13Corg) were determined. Thereafter, KL was isolated from the samples, as the insoluble residue obtained after HF/HCl treatment. KL chemical composition was investigated via spectroscopic (FTIR, solid state 13C and 15N NMR) and pyrolytic (Curie point pyrolysis–gas chromatography–mass spectrometry) methods, and the morphological features were examined by scanning and transmission electron microscopy. Similar morphological features and chemical composition were observed for the three KLs and they suggested that the selective preservation of land-plant derived material as well as of resistant aliphatic biomacromolecules (probably derived from cell walls of freshwater microalgae) was the main process involved in KL formation. Besides, some melanoidin-type macromolecules (formed via the degradation-recondensation of products mainly derived from proteinaceous material) and/or some encapsulated proteins also contributed to the KL chemical structure. 相似文献
5.
Hendrik Jan van der Woerd Anouk Blauw Louis Peperzak Reinold Pasterkamp Steef Peters 《Journal of Sea Research》2011,65(2):195-204
Phaeocystis blooms in the Southern Bight of the North Sea may cause damage to the aquatic ecosystem and to commercial mussel cultures at the entrance of the Oosterschelde estuary. In this paper the potential for early detection of Phaeocystis blooms in Dutch coastal waters is studied, using a combination of field data, satellite observations and hydrodynamic- and biological modelling. For the spring bloom period in the year 2003 MERIS chlorophyll-a maps, derived with the HYDROPT algorithm for coastal waters, were compared to in-situ measurements at stations off the coast in de Voordelta and the results of the GEM biogeochemical model.The analysis shows that the spatial and temporal variability in Phaeocystis abundance and total biomass (expressed by the Chl-a concentration) during spring is large. It is confirmed that blooms may develop off shore and show a tendency to accumulate within 10 km from the coastline, giving rise to rapid biomass accumulation at the mouth of the multiple estuaries in the Voordelta. Based on the outcome of this study an early warning system is proposed that notifies local water managers and shellfish growers for potentially harmful Phaeocystis bloom formation. 相似文献
6.
Currently, the effect of dike breaches on downstream discharge partitioning and flood risk is not addressed in flood safety assessments. In a bifurcating river system, a dike breach may cause overland flows which can change downstream flood risk and discharge partitioning. This study examines how dike breaches and overflow affect overland flow patterns and discharges of the rivers of the Rhine delta. For extreme discharges, an increase in flood risk along the river branch with the smallest discharge capacity was found, while flood risk along the other river branches was reduced. Therefore, dike breaches and resulting overland flow patterns must be included in flood safety assessments.
相似文献7.
Natural Hazards - In this reply, we would like to comment on the discussion paper of AlQasimi and Mahdi (Nat Hazards 97:1–4, 2020. https://doi.org/10.1007/s11069-020-03904-1 ). We discuss... 相似文献
8.
Benjamin de Brye Anouk de Brauwere Olivier Gourgue Tuomas Kärnä Jonathan Lambrechts Richard Comblen Eric Deleersnijder 《Coastal Engineering》2010
We report on the development and validation of a coupled two- and one-dimensional finite-element model for the Scheldt tributaries, river, estuary and region of fresh water influence (ROFI). The hydrodynamic equations are solved on a single, unstructured, multi-scale mesh stretching from the shelf break to the Scheldt tributaries. The tide is forced on the shelf break and propagates upstream in the riverine network. Upstream boundaries lie on sluices or outside of the region of tidal dominance where daily averaged discharges are imposed. Two-dimensional, depth-averaged shallow water equations are solved by means of the discontinuous Galerkin (DG) method over the marine and estuarine parts of the computational domain. In the rivers, however, one-dimensional equations are dealt with using the DG method with the addition of a technique to cope with confluence points. Model parameters are carefully calibrated, leading to the simulation of wind- and tide-forced flows that are in excellent agreement with available data. The diffusivity in the transport equation is calibrated using time series of salinity at various locations in the estuary. Finally, the Lagrangian residual transport in the estuary and the adjacent coastal zone is investigated. This work is a major step towards an integrated model for studying the dynamics of waterborne contaminants and the water renewal timescales in the Scheldt land-sea continuum. 相似文献
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