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M. van der Wegen

Bio: M. van der Wegen is an academic researcher from UNESCO-IHE Institute for Water Education. The author has contributed to research in topics: Beach morphodynamics & Sediment transport. The author has an hindex of 15, co-authored 31 publications receiving 1010 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the authors investigated the long-term evolution of estuarine morphodynamics with special emphasis on the impact of pattern formation using a two-dimensional (2-D), numerical, process-based model.
Abstract: [1] The research objective is to investigate long-term evolution of estuarine morphodynamics with special emphasis on the impact of pattern formation. Use is made of a two-dimensional (2-D), numerical, process-based model. The standard model configuration is a rectangular 80 km long and 2.5 km wide basin. Equilibrium conditions of the longitudinal profile are analyzed using the model in 1-D mode after 8000 years. Two-dimensional model results show two distinct timescales. The first timescale is related to pattern formation taking place within the first decades and followed by minor adaptation according to the second timescale of continuous deepening of the longitudinal profile during 1600 years. The resulting longitudinal profiles of the 1-D and 2-D runs are similar apart from small deviations near the mouth. The 2-D results correspond well to empirically derived relationships between the tidal prism and the channel cross section and between the tidal prism and the channel volume. Also, comparison between the current model results and data from the Western Scheldt estuary (in terms of bar length, hypsometry, percentage of intertidal area and values for the ratio of shoal volume and channel volume against the ratio of tidal amplitude and water depth) shows satisfying agreement. On the basis of the model results a relationship for a characteristic morphological wavelength was derived on the basis of the tidal excursion and the basin width and an exponentially varying function was suggested for describing a dimensionless hypsometric curve for the basin. Furthermore, special attention is given to an analysis of the numerical morphodynamic update scheme applied.

248 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the interaction between different scales and spatial scales of the morphodynamic system in alluvial, coastal plain estuaries and the evolution of the estuarine morphodynamic evolution.
Abstract: The morphodynamic system in alluvial, coastal plain estuaries is complex and characterized by various timescales and spatial scales. The current research aims to investigate the interaction between these different scales as well as the estuarine morphodynamic evolution. Use is made of a process-based, numerical model describing 2-D shallow water equations and a straightforward formulation of the sediment transport and the bed level update. This was done for an embayment with a length of 80 km on a timescale of 3200 years, with and without bank erosion effects. Special emphasis is put on analyzing the results in terms of energy dissipation. Model results show that the basins under consideration evolve toward a state of less morphodynamic activity, which is reflected by (among others) relatively stable morphologic patterns and decreasing deepening and widening of the basins. Closer analysis of the tidal wave shows standing wave behavior with resonant characteristics. Under these conditions, results suggest that the basins aim for a balance between the effect of storage and the effect of fluctuating water level on wave celerity with a negligible effect of friction. Evaluating the model results in terms of energy dissipation reflects the major processes and their timescales (pattern formation, widening, and deepening). On the longer term the basin-wide energy dissipation decreases at a decreasingly lower rate and becomes more uniformly distributed along the basin. Analysis by an entropy-based approach suggests that the forced geometry of the configurations prevents the basins from evolving toward a most probable state.

126 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used a 2DH process-based morphodynamic model (Delft3D) on a schematized model domain, with dimensions similar to the Ameland inlet in the Dutch Wadden Sea starting from a flat bed the models are forced by tides only Short-term simulations are made to explore the hydrodynamic characteristics and initial sedimentation and erosion patterns Long-term morphodynamic simulations are employed to investigate the governing parameters of the main inlet channel and the ebb-tidal delta evolution Sensitivity of the evolution is described in terms of initial

101 citations

Journal ArticleDOI
TL;DR: In this article, a 3D morphodynamic, process-based numerical model (Delft3D) is proposed to investigate the processes governing the evolution of major morphological features in alluvial estuaries as well as their morphodynamic interaction with the geometry by means of a three-dimensional model.

96 citations

Journal ArticleDOI
TL;DR: In this paper, the impact of river discharge on estuarine morphodynamics is examined in a 560 km long tidal basin based on a 1-dimensional model (Delft3D).
Abstract: Numerous research efforts have been devoted to understanding estuarine morphodynamics under tidal forcing. However, the impact of river discharge on estuarine morphodynamics is insufficiently examined. Inspired by the Yangtze Estuary, this work explores the morphodynamic impact of river discharge in a 560 km long tidal basin based on a 1-D model (Delft3D). The model considers total load sediment transport and employs a morphodynamic updating scheme to achieve long-term morphodynamic evolution. We analyze the role of Stokes drift, tidal asymmetry, and river discharge in generating tidal residual sediment transport. Model results suggest that morphodynamic equilibrium is approached within millennia by vanishing spatial gradients of tidal residual sediment transport. We find that the interaction between ebb-directed Stokes return flow/river flow with tides is an important mechanism that flushes river-supplied sediment seaward. Increasing river discharge does not induce continuously eroded or accreted equilibrium bed profiles because of the balance between riverine sediment supply and sediment flushing to the sea. An intermediate threshold river discharge can be defined which leads to a deepest equilibrium bed profile. As a result, the shape (concavity or convexity) of the equilibrium bed profiles will adapt with the magnitude of river discharge. Overall, this study reveals the significant role of river discharge in controlling estuarine morphodynamics by supplying sediment and reinforcing ebb-directed residual sediment transport.

93 citations


Cited by
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Book ChapterDOI
02 Mar 2001

984 citations

Journal ArticleDOI
TL;DR: In this paper, the authors discuss the morphodynamics of different units that characterize a tidal inlet system: the overall system, the ebb-tidal delta, the tidal channels, channel networks, tidal bars and meanders, and finally the intertidal zone of tidal flats and salt marshes.
Abstract: In this review we discuss the morphodynamics of tidal inlet systems that are typical of barrier coasts formed during a period of continuous sea-level rise during the Holocene. The morphodynamics concerns feedbacks between three major components: the hydrodynamics of tidal currents and wind waves; the erosion, deposition, and transport of sediment under the action of the former hydrodynamic agencies; and the morphology proper, which results from the divergence of the sediment transport. We discuss the morphodynamics of the different units that characterize a tidal inlet system: the overall system, the ebb-tidal delta, the tidal channels, channel networks, tidal bars and meanders, and finally the intertidal zone of tidal flats and salt marshes. In most of these units, stability analysis is a major guide to the establishment of equilibrium structures.

285 citations

01 Dec 2006
TL;DR: In this article, an ecomorphodynamic model was proposed to investigate the response of tidal morphologies to different scenarios of sediment supply, colonization by halophytes, and changing sea level.
Abstract: We propose an ecomorphodynamic model which conceptualizes the chief land-forming processes operating on the intertwined, long-term evolution of marsh platforms and embedded tidal networks. The rapid network incision (previously addressed by the authors) is decoupled from the geomorphological dynamics of intertidal areas, governed by sediment erosion and deposition and crucially affected by the presence of vegetation. This allows us to investigate the response of tidal morphologies to different scenarios of sediment supply, colonization by halophytes, and changing sea level. Different morphological evolutionary regimes are shown to depend on marsh ecology. Marsh accretion rates, enhanced by vegetation growth, and the related platform elevations tend to decrease with distance from the creek, measured along suitably defined flow paths. The negative feedback between surface elevation and its inorganic accretion rate is reinforced by the relation between plant productivity and soil elevation in Spartina-dominated marshes and counteracted by positive feedbacks in multispecies-vegetated marshes. When evolving under constant sea level, unvegetated and Spartina-dominated marshes asymptotically tend to mean high water level (MHWL), different from multiple vegetation species marshes, which can make the evolutionary transition to upland. Equilibrium configurations below MHWL can be reached under constant rates of sea level rise, depending on sediment supply and vegetation productivity. Our analyses on marine regressions and transgressions show that when the system is in a supply-limited regime, network retreat and expansion (associated with regressions and transgressions, respectively) tend to be cyclic. Conversely, in a transport-limited regime, network reexpansion following a regression tends to take on a new configuration, showing a hysteretic behavior. Copyright 2007 by the American Geophysical Union.

276 citations

Journal ArticleDOI
21 Sep 2011-PLOS ONE
TL;DR: A series of models are linked to investigate responses of California's San Francisco Estuary-Watershed system to two contrasting scenarios of climate change, and nine indicators of changing climate, hydrology and habitat quality are presented.
Abstract: Background: Accumulating evidence shows that the planet is warming as a response to human emissions of greenhouse gases. Strategies of adaptation to climate change will require quantitative projections of how altered regional patterns of temperature, precipitation and sea level could cascade to provoke local impacts such as modified water supplies, increasing risks of coastal flooding, and growing challenges to sustainability of native species. Methodology/Principal Findings: We linked a series of models to investigate responses of California’s San Francisco Estuary-Watershed (SFEW) system to two contrasting scenarios of climate change. Model outputs for scenarios of fast and moderate warming are presented as 2010–2099 projections of nine indicators of changing climate, hydrology and habitat quality. Trends of these indicators measure rates of: increasing air and water temperatures, salinity and sea level; decreasing precipitation, runoff, snowmelt contribution to runoff, and suspended sediment concentrations; and increasing frequency of extreme environmental conditions such as water temperatures and sea level beyond the ranges of historical observations. Conclusions/Significance: Most of these environmental indicators change substantially over the 21 st century, and many would present challenges to natural and managed systems. Adaptations to these changes will require flexible planning to cope with growing risks to humans and the challenges of meeting demands for fresh water and sustaining native biota. Programs of ecosystem rehabilitation and biodiversity conservation in coastal landscapes will be most likely to meet their objectives if they are designed from considerations that include: (1) an integrated perspective that river-estuary systems are influenced by effects of climate change operating on both watersheds and oceans; (2) varying sensitivity among environmental indicators to the uncertainty of future climates; (3) inevitability of biological community changes as responses to cumulative effects of climate change and other drivers of habitat transformations; and (4) anticipation and adaptation to the growing probability of ecosystem regime shifts.

222 citations

Journal ArticleDOI
TL;DR: A review of field observations and modeling studies set in tidal river environments as diverse as the Amazon in Brazil, the Columbia, Fraser and Saint Lawrence in North America, the Yangtze and Pearl in China, and the Berau and Mahakam in Indonesia is provided in this paper.
Abstract: Tidal rivers are a vital and little studied nexus between physical oceanography and hydrology. It is only in the last few decades that substantial research efforts have been focused on the interactions of river discharge with tidal waves and storm surges into regions beyond the limit of salinity intrusion, a realm that can extend inland hundreds of kilometers. One key phenomenon resulting from this interaction is the emergence of large fortnightly tides, which are forced long waves with amplitudes that may increase beyond the point where astronomical tides have become extinct. These can be larger than the linear tide itself at more landward locations, and they greatly influence tidal river water levels and wetland inundation. Exploration of the spectral redistribution and attenuation of tidal energy in rivers has led to new appreciation of a wide range of consequences for fluvial and coastal sedimentology, delta evolution, wetland conservation, and salinity intrusion under the influence of sea level rise and delta subsidence. Modern research aims at unifying traditional harmonic tidal analysis, nonparametric regression techniques, and the existing understanding of tidal hydrodynamics to better predict and model tidal river dynamics both in single-thread channels and in branching channel networks. In this context, this review summarizes results from field observations and modeling studies set in tidal river environments as diverse as the Amazon in Brazil, the Columbia, Fraser and Saint Lawrence in North America, the Yangtze and Pearl in China, and the Berau and Mahakam in Indonesia. A description of state-of-the-art methods for a comprehensive analysis of water levels, wave propagation, discharges, and inundation extent in tidal rivers is provided. Implications for lowland river deltas are also discussed in terms of sedimentary deposits, channel bifurcation, avulsion, and salinity intrusion, addressing contemporary research challenges.

214 citations