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This research aims to investigate the morphodynamics of the Wulan River estuary in Demak Regency using the integration of multispectral remote sensing images and numerical modeling. In this study, PlanetScope for a manual-visual analysis of estuary morphodynamics and Sentinel-2 MSI Level 2A to obtain periodic total suspended solids (TSS) information for the east and west monsoon seasons. MIKE by DHI software used to develop hydrodynamic numerical modeling in order to characterize the current circulation and sediment transport model. Based on a marine cartography aspect, the obtained results illustrated that the climatological phenomenon of seasonal forcing plays a role in the development of the current circulation and indirectly influences the sediment transport. During the west season, the morphodynamics in the Wulan River estuary are much more massive and significant as compared to the east season. A projection of the deposition that results from the sediment transport is described in the bed-thickness change; this occurs in the western part of the Wulan River estuary during the east season, while the bed-thickness change occurs predominantly in the northern part during the west season (where there was previously a beach sandbar phenomenon). This was verified through multi-temporal satellite imagery that the deposition that occurs in the northern part of the Wulan River estuary during the west season is increasingly progressive and massive. [ABSTRACT FROM AUTHOR]

This study aims to investigate the hydrodynamic-morphological interactions on a microtidal intermediate-dissipative beach under low to moderate wave energy conditions using field measurements during two climatic seasons. The separate contributions of currents, sea-swell waves, and infragravity waves to high- and low-frequency sediment fluxes were analyzed. The infragravity wave energy was more relevant near the swash zone than in other areas. Although the currents are the primary suspended sediment transport mechanism, the results suggest that the waves are an important driver of sediment suspension from the seabed. The results indicate that Sea-Swell (SS) waves and cross-shore currents are the prevailing hydrodynamic factors in nearshore sediment transport, and the cross-shore suspended sediment transport rates are higher than those in alongshore transport. The submerged bar intensified during the wet season (1–4 November 2018) when the wave height intensities were lower, contrary to the dry season (24–25 March 2018). Significant accretion nearshore was identified (in the subaerial beach) during the wet season when the suspended sediments were greater, the SS-wave heights nearshore were lower, and sediment flux was directed onshore. A notorious erosion was distinguished during the dry season. The most representative volume changes occurred during the dry season (with high erosion), which is attributed to the high SS-wave energy. [ABSTRACT FROM AUTHOR]

Coastal erosion poses significant challenges to shoreline management, exacerbated by rising sea levels and changing climate patterns. This study investigates the influence of gap spacing between semicircular coastal defence structures on shoreline dynamics during storm events. The innovative design of these structures aims to induce a drift reversal of prevalent sediment transport while avoiding interruption of alongshore sediment drift, thus protecting the beach. Three different gap spacings, ranging from 152 m to 304 m, were analysed using the XBeach numerical model, focusing on storm morphodynamic behaviour. Methodologically, hydrodynamic and morphodynamic analyses were conducted to understand variations in significant wave heights adjacent to the structures, in accretion and erosion volumes, and changes in bed level under storm conditions. The study aims to elucidate the complex interaction between engineered coastal protection solutions and natural coastal processes, providing practical insights for coastal management practices. Results indicate that installing semicircular coastal defence structures influences sediment dynamics during storm events, effectively protecting stretches of the coast at risk. Optimal gap spacing between structures is crucial to mitigating coastal erosion and enhancing sediment accumulation, offering a sustainable shoreline protection approach. The findings underscore the importance of balanced location selection to optimize protection benefits while minimizing adverse morphological effects. Overall, this research contributes to advancing knowledge of hydro-morphological phenomena essential for effective coastal engineering and informs the design and implementation of more sustainable coastal protection strategies in the face of increasing coastal erosion and sea level rise challenges. [ABSTRACT FROM AUTHOR]

The shallow-water and multilayer hydrostatic models have been commonly used to analyze the problems of a sediment-laden, plane open-channel flow. The models are adequate to solve a quasi-hydrostatic flow problem, but their accuracy deteriorates as the e ects of the vertical acceleration gain in significance. Herein, a higher-order numerical model for treating the problems of unsteady, plane open-channel flow over a movable bed is proposed. In this model, the flow hydrodynamics is governed by the depth-averaged Boussinesq-type equations, and the bed morphodynamics is determined by an Exner-type equation and additional equations describing the non-equilibrium transports of suspended load and bed load. A hybrid finite-volume and finite-di erence scheme was used to discretize and solve the governing equations, yielding solutions that are in satisfactory agreement with the experimental data. Overall, the results of the proposed model for the temporal free-surface profile and bed evolution were fairly adequate. For the two particular cases considered, however, the quality of its results was moderately a ected by the e ects of the three-dimensional characteristics of the dam-break flow and the sliding of the dike body due to sub-surface flow. The results of this investigation highlight the importance of including a higher-order Boussinesq-type correction for refining sediment transport computations. [ABSTRACT FROM AUTHOR]

This study aims to investigate the hydrodynamic-morphological interactions on a microtidal intermediate-dissipative beach under low to moderate wave energy conditions using field measurements during two climatic seasons. The separate contributions of currents, sea-swell waves, and infragravity waves to high- and low-frequency sediment fluxes were analyzed. The infragravity wave energy was more relevant near the swash zone than in other areas. Although the currents are the primary suspended sediment transport mechanism, the results suggest that the waves are an important driver of sediment suspension from the seabed. The results indicate that Sea-Swell (SS) waves and cross-shore currents are the prevailing hydrodynamic factors in nearshore sediment transport, and the cross-shore suspended sediment transport rates are higher than those in alongshore transport. The submerged bar intensified during the wet season (1–4 November 2018) when the wave height intensities were lower, contrary to the dry season (24–25 March 2018). Significant accretion nearshore was identified (in the subaerial beach) during the wet season when the suspended sediments were greater, the SS-wave heights nearshore were lower, and sediment flux was directed onshore. A notorious erosion was distinguished during the dry season. The most representative volume changes occurred during the dry season (with high erosion), which is attributed to the high SS-wave energy.

Coastal erosion poses significant challenges to shoreline management, exacerbated by rising sea levels and changing climate patterns. This study investigates the influence of gap spacing between semicircular coastal defence structures on shoreline dynamics during storm events. The innovative design of these structures aims to induce a drift reversal of prevalent sediment transport while avoiding interruption of alongshore sediment drift, thus protecting the beach. Three different gap spacings, ranging from 152 m to 304 m, were analysed using the XBeach numerical model, focusing on storm morphodynamic behaviour. Methodologically, hydrodynamic and morphodynamic analyses were conducted to understand variations in significant wave heights adjacent to the structures, in accretion and erosion volumes, and changes in bed level under storm conditions. The study aims to elucidate the complex interaction between engineered coastal protection solutions and natural coastal processes, providing practical insights for coastal management practices. Results indicate that installing semicircular coastal defence structures influences sediment dynamics during storm events, effectively protecting stretches of the coast at risk. Optimal gap spacing between structures is crucial to mitigating coastal erosion and enhancing sediment accumulation, offering a sustainable shoreline protection approach. The findings underscore the importance of balanced location selection to optimize protection benefits while minimizing adverse morphological effects. Overall, this research contributes to advancing knowledge of hydro-morphological phenomena essential for effective coastal engineering and informs the design and implementation of more sustainable coastal protection strategies in the face of increasing coastal erosion and sea level rise challenges.

Offshore anthropogenic activities such as the installation of Offshore Renewable Energy (ORE) developments and sediment extraction for marine aggregates have been shown to disrupt current flow, wave propagation, and sediment transport pathways, leading to potential environmental instability. Due to the complexity of the interconnected sediment transport pathways in the south-western Irish Sea combined with an increase in planned anthropogenic activities, the assessment of this risk is imperative for the development of a robust marine spatial plan. Subsequently, this study uses two-dimensional morphological modelling to build upon previous studies to assess the dependency of Arklow Bank's local sediment transport regime on external sediment sources. Additionally, scenario modelling is used to identify vulnerable areas of this offshore linear sand bank to wind and wave-forcing and to examine the nature of this impact. A sediment budget is estimated for Arklow Bank, whereby seven source and nine sink pathways are identified. New evidence to support the exchange of sediment between offshore sand banks and offshore independent sand wave fields is also provided. The areas of the bank most vulnerable to changes in external sediment sources and the addition of wind- and wave-induced flow are analogous. These high vulnerability zones (HVZs) align with regions of residual cross-flow under pure current conditions. The restriction of sediment sources off the southern extent of Arklow Bank impacts erosion and accretion patterns in the mid- and northern sections of the bank after just one lunar month of simulation. Where tidal current is the primary driver of sand bank morphodynamics, wind- and wave-induced flow is shown to temporarily alter sediment distribution patterns. Wind and wave-induced flow can both accelerate and decelerate the east-west fluctuation of the upper slopes of the bank, yet the nature of this impact is inconsistent due to the misalignment of the directionality of these two forces. The methods and new knowledge derived from this study are directly applicable to tidally-dominated environments outside the Irish Sea. [ABSTRACT FROM AUTHOR]

The formation of sandbars, spits and shoals are common at the inlet mouth particularly along coasts dominated by longshore sediment transport. These formations act as barriers, thus preventing the ingress of tidal flow. Sandbar and spit formation can be preferably averted by the construction of a pair of training walls, after which monitoring the behaviour of the stability of the tidal inlet is of prime importance. In cases where the tidal inlet meets a riverine estuary, the inlet dimensions and rate of littoral transport are primarily governed by the volume of water exchanged at the inlet mouth and the ebbing tidal currents, respectively. This paper discusses the case study of a micro-tidal inlet at Karaikal (10°54′52″N; 79°51′09″E), situated along the southeast coast of the Indian peninsula. This inlet coincides with the mouth of the Arasalar estuary, a tributary of the Cauvery river. A numerical model using the finite volume method is applied to estimate morphodynamic changes in the inlet channel driven by tide-induced currents and riverine discharge during the North-East monsoon season and the same has been validated through field measured data. The ultimate aim is to arrive at mitigation measures to combat siltation within the inlet. [ABSTRACT FROM AUTHOR]

Offshore anthropogenic activities such as the installation of Offshore Renewable Energy (ORE) developments and sediment extraction for marine aggregates have been shown to disrupt current flow, wave propagation, and sediment transport pathways, leading to potential environmental instability. Due to the complexity of the interconnected sediment transport pathways in the south-western Irish Sea combined with an increase in planned anthropogenic activities, the assessment of this risk is imperative for the development of a robust marine spatial plan. Subsequently, this study uses two-dimensional morphological modelling to build upon previous studies to assess the dependency of Arklow Bank’s local sediment transport regime on external sediment sources. Additionally, scenario modelling is used to identify vulnerable areas of this offshore linear sand bank to wind and wave-forcing and to examine the nature of this impact. A sediment budget is estimated for Arklow Bank, whereby seven source and nine sink pathways are identified. New evidence to support the exchange of sediment between offshore sand banks and offshore independent sand wave fields is also provided. The areas of the bank most vulnerable to changes in external sediment sources and the addition of wind- and wave-induced flow are analogous. These high vulnerability zones (HVZs) align with regions of residual cross-flow under pure current conditions. The restriction of sediment sources off the southern extent of Arklow Bank impacts erosion and accretion patterns in the mid- and northern sections of the bank after just one lunar month of simulation. Where tidal current is the primary driver of sand bank morphodynamics, wind- and wave-induced flow is shown to temporarily alter sediment distribution patterns. Wind and wave-induced flow can both accelerate and decelerate the east-west fluctuation of the upper slopes of the bank, yet the nature of this impact is inconsistent due to the misalignment of the directionality of these two forces. The methods and new knowledge derived from this study are directly applicable to tidally-dominated environments outside the Irish Sea.

Shipwrecks are important cultural heritage sites offshore. In many instances, given their often long-term emplacement on the seafloor, they offer natural laboratories to study complex interactions between human-induced obstacles and seabed dynamics. Such interactions and induced sediment mobility also pose significant threats to offshore engineering infrastructure, such as turbine monopile foundations. Traditional methods can struggle to capture the nuance of these processes, with real-world surveys measuring effects only after installation, and laboratory models suffering from scale-down inaccuracies. Computational fluid dynamics (CFD) modelling offers an effective means of investigating the effects of obstacles on seabed dynamics, and by using shipwrecks as proxies for infrastructure, it can utilize long-term datasets to verify its predictions. In this study, high-resolution temporal bathymetric data were used in, and to verify, CFD modelling to investigate the interactions between hydro- and sediment dynamics at a shipwreck site in a tidally dominated wreck site. From this comparison, simulations of bed shear stress and scalar transport correlate well with known areas of erosion and deposition, serving as a basis for future scour prediction studies and creating effective tools in offshore renewable infrastructure planning and de-risking. [ABSTRACT FROM AUTHOR]

The phase-averaged and depth-integrated coastal morphodynamic model, XBeach-Surfbeat, was investigated for its capability of predicting the cross-shore hydrodynamics and morphodynamics in the inner surf zone by simulating the storm-induced berm erosion, sediment transport, and subsequent sand bar formation. By utilizing a comprehensive hydrodynamic and morphodynamic dataset measured in a large wave flume and high-fidelity 3D large-eddy simulation (LES) data, a rigorous model validation was conducted to assess its capability in predicting inner-surf zone hydrodynamics and to explore how the improved hydrodynamic performance impacts the predicted morphodynamics. Using the default model parameters of the model, the undertow was overestimated with the peak magnitude being 30%–35% larger in the inner surf zone. Combining Monte Carlo simulation, the optimum hydrodynamic calibration for the simulated undertow was achieved when the roller energy dissipation parameter (β) was maintained below 0.1, and the threshold water depth (h min) exceeded 0.25 m. The calibrated undertow improved the morphodynamic predictions by reducing the excessive berm erosion (Event I) and sand bar growth in the inner surf zone (Event II). Further improved morphodynamic predictions were achieved by calibrating sediment transport parameters, including the onshore sediment transport coefficient (γ u a ) and the bore interval coefficient (T b f a c ) associated with turbulence-bed interaction. A consistent set of optimized model coefficients for the model is shown to be effective in simulating the entire erosive event (combined Events I and II). This study reveals that further improvement of the model's capability may require incorporating new parameterizations and physics, such as wave-breaking-induced turbulence and wave nonlinearity associated with sediment transport in the inner surf and swash zones. • Berm-bar sediment exchange during an erosive event in wave flume is modeled by a phase-averaged coastal morphodynamic model. • Accurate undertow modeling is needed for robust prediction of beach profiles in the inner surf zone. • Wave-breaking-induced turbulence works in conjunction with wave skewness/asymmetry to drive onshore sediment transport. [ABSTRACT FROM AUTHOR]

Many coastal regions around the globe experience land loss due to high relative sea level rise rates, declining sediment supply, and a host of other anthropogenic factors. To evaluate possible restoration strategies, we developed a computationally efficient Simplified Biophysical Model (SBM). The SBM includes hydrodynamic, morphodynamic, and marsh inundation components. The hydrodynamic and mineral sediment processes of the SBM are based on open source Delft3D models. The marsh inundation MATLAB module is a simplified vegetation response to salinity and inundation used to estimate annual organic accretion rates. Organic accretion is added annually to the morphodynamic calculations of mineral sediment. The typical run time for the SBM for an area of 4500 km2 is ∼0.8, 2.5, and 4.7 days real time for one, three, and five decade simulations, respectively which is considered a computationally efficient for modeling decadal landscape evolution. The utility of the SBM was demonstrated through an application to assess the performance of a sediment diversion in the Barataria Basin in Louisiana, USA. The model results demonstrate the importance of incorporating the impact of salinity and inundation effects on the resilience of marshes subjected to high rates of relative sea level rise. Further, the sediment reduction analysis confirms the critical impact of the Mississippi River sediment decline on potential land building from sediment diversions where 1.5%, and 3% annual declining rates show a reduction in net land gain due to Mid-Barataria Sediment Diversion operation of 30% and 50 %, respectively. This highlights the importance of considering the Mississippi River sediment supply decline in restoration projects' planning and specifically, sediment diversions. • A new simplified biophysical model (SBM) was developed to study deltaic ecosystems. • A new marsh inundation module was coupled with Delft3D to estimate annual organic accretion rates. • The SBM model computationally efficient tool to evaluate coastal restoration strategies. • The Barataria basin in Louisiana, USA is used as a case study to illustrate the model applicability. • Decline of the Mississippi River sediment load is of major concern for coastal restoration activities. [ABSTRACT FROM AUTHOR]

The dense populations that inhabit global coastlines have an uncertain future due to increased flooding, storms, and human modification. The channel networks of deltas and marshes that plumb these coastlines present diverse architectures, including well‐studied dendritic topologies. However, the quasi‐stable loops that exist in nearly all coastal networks have not yet been explained. We present a model for self‐organizing networks inspired by vascular biophysics to show that loops emerge when the relative forcings between rivers and tides are comparable, resulting in interplay between hydrodynamic forcings at short time scales relative to network evolution. Using field data and satellite imaging, we confirm this control on 21 field networks. Our comparison provides compelling evidence that hydrodynamic fluctuations are capable of stabilizing loops in geophysical systems. Plain Language Summary: How do coastal channel networks form, and what are their stable configurations? The answers to these questions are essential for predicting how coasts will change under growing human and climatic stresses like sea level rise, river damming, or river engineering. Loops exist in most coastal networks, yet physical controls on the initiation and stability of this fundamental network feature are unknown. We use a model of channel network evolution to show that loops form only when there is interplay between distinct flow patterns. Field data also show that river‐tidal interplay coincides with the presence or absence of loops in networks on coasts. This link between network structure and flow patterns can indicate a network's equilibrium state or inform how it might react to changing conditions. Key Points: No theory exists to explain the presence of quasi‐stable loops in coastal channel networksA simple model that includes interaction between river and periodic tidal forcing produces loops at equilibriumAn analysis of 21 coastal channel networks generally agrees with the simulations [ABSTRACT FROM AUTHOR]

• This study demonstrate the benefits of using varying parameterization of calibration parameters, viz., horizontal eddy viscosity and bottom friction coefficient in SWE models in terms of prediction quality and reliability. • This paper contributes to the knowledge by proposing a new and simple approach in parameterizing the horizontal eddy viscosity, the efficiency of which is validated with the field data. • The contribution of spatially varying bottom friction coefficient in improving the results is also investigated and reported in this paper. • The novelty of this study concerning hydrodynamics and morphodynamics is new parameterization of the horizontal eddy viscosity based on velocity and length scale of computational mesh, appraising the efficiency of spatio-temporally varying parameterization with field data. The horizontal eddy viscosity (ε) and bottom friction coefficient (K br) are important hydrodynamic parameters in the computation of flow fields that dictate the morphodynamics. The effect of the variations in ε and K br as well as their combination on the prediction of hydrodynamics and morphodynamics in the Cochin harbor and adjoining nearshore area (9.9312° N, 76.2673° E) has been investigated in detail. A tidal circulation model to solve the shallow water equation is applied with the different parameterizations of ε and K br. In order to understand its effect, ε is expressed as a function of depth averaged velocity and length scale of computation mesh, whereas K br is expressed as a function of depth. The validation of the model is carried out with the measured currents. The improvement in the hydrodynamic and morphodynamic predictions is demonstrated by implementing the spatially and temporally varying ε The predictions are further improved by implementing a spatially varying K br. It is seen that the simulations with varying ε and K br predict the morphodynamic behavior close to the field values. The performance of the model predictions is discussed in terms of R2, RMSE and BSS (Brier Skill Score). [ABSTRACT FROM AUTHOR]

Shipwrecks are important cultural heritage sites offshore. In many instances, given their often long-term emplacement on the seafloor, they offer natural laboratories to study complex interactions between human-induced obstacles and seabed dynamics. Such interactions and induced sediment mobility also pose significant threats to offshore engineering infrastructure, such as turbine monopile foundations. Traditional methods can struggle to capture the nuance of these processes, with real-world surveys measuring effects only after installation, and laboratory models suffering from scale-down inaccuracies. Computational fluid dynamics (CFD) modelling offers an effective means of investigating the effects of obstacles on seabed dynamics, and by using shipwrecks as proxies for infrastructure, it can utilize long-term datasets to verify its predictions. In this study, high-resolution temporal bathymetric data were used in, and to verify, CFD modelling to investigate the interactions between hydro- and sediment dynamics at a shipwreck site in a tidally dominated wreck site. From this comparison, simulations of bed shear stress and scalar transport correlate well with known areas of erosion and deposition, serving as a basis for future scour prediction studies and creating effective tools in offshore renewable infrastructure planning and de-risking.

Fluvial sediment pulses are associated with a sudden and major increase in sediment supply to riverine environments. Their occurrence can be triggered by natural or anthropogenic factors or processes, including landslides, debris flows from tributaries, volcanic eruptions, dam removals, and mining‐related activities. To predict their propagation, decoupled (clear‐water) models are commonly used, despite shortcomings identified when simulating the initial propagation phase and the existence of coupled (sediment‐laden) models. Herein, a framework for improving the accuracy of modeling efforts that simulate fluvial sediment pulse propagation dynamics is presented. The framework is centered on a physics‐based criterion formed by a dimensionless parameter ξ and its threshold condition ξcr. Comparison with laboratory and field studies shows that ξ indicates the relative importance of the terms neglected in decoupled models and that its threshold condition ξcr effectively sets an upper limit for their application. Results show that decoupled models are inaccurate when ξ > ξcr but become sufficient when ξ < ξcr. When applied to well‐monitored fluvial sediment pulses, the framework quantifies the two‐phase propagation dynamics observed in the field, showing an initial phase characterized by ξ > ξcr and a subsequent phase characterized by ξ ≤ ξcr. Overall, the framework provides a physics‐based quantitative approach that addresses the limitations of decoupled models by setting an upper limit for their range of validity. Plain Language Summary: Sediment pulses are disturbances that occur in rivers due to various natural and human‐induced causes, including landslides, volcanic eruptions, dam removals, and mining‐related activities. They deposit large amounts of loose material, disrupting the river's ability to move water and sediment efficiently. As a result, their occurrence is frequently associated with sediment accumulation in the channel, damage of infrastructure, and impairment of water quality. In this study, a framework to better understand and quantify how rivers respond to these types of disturbances is presented. The framework is centered on an analytical parameter and its limiting condition. It is applied, first, to determine the limitations of frequently used numerical tools, and second, to examine conceptual models developed from field observations. Results indicate that the framework can be effectively used to improve the accuracy of frequently used numerical tools, as well as to provide an analytical and quantitative understanding of field‐based observations. Ultimately, this study contributes toward improving our ability to predict how rivers respond to and recover from the impacts of sediment‐supply disturbances. Key Points: A framework is presented to quantify river response to sediment‐supply disturbances such as those that follow dam removals or landslidesPhysics‐based criterion sets a quantitative method for identifying hydro‐morphodynamic conditions that render decoupled models sufficientPhysics‐based criterion quantifies two‐phase sediment pulse propagation dynamics observed in the field [ABSTRACT FROM AUTHOR]

Global climate change is altering the frequency and intensity of extreme weather events such as typhoons and cold fronts, and this is inducing physical changes and adaptions in estuaries and coasts. We conducted a field campaign on the subaqueous Changjiang Delta front in September 2019 to improve understanding of storm impact on short-term hydro-morphodynamics. Over an 11-day period, during which both typhoon and cold front events occurred, in-situ data including flow velocities, suspended sediment concentrations (SSC), and bed-level changes were acquired using bottom tripod and buoyage systems, Significant wave height reached 5.0 m during the typhoon, and the depth-averaged current velocity increased to 1.7 m/s. The net near-bottom sediment flux was in the same direction as the wind and was 5.5 times of that under calm weather. During the cold-front, significant wave height reached 2.5 m, and the near-bottom SSC increased to 7.0 kg/m3. Bed-level changes were small (<2 cm) under pre-storm weather, while net deposition and erosion reached 15.8 cm and 16.8 cm, respectively, during the typhoon. Short-term changes in the sediment source-to-sink regime were detected in the subaqueous Changjiang Delta. The cold front enhances seaward sediment flushing from the delta towards the sea, while the typhoon drives sediment transport from the subaqueous delta towards Hangzhou Bay. We also observed rapid bed-level recovery following these extreme events. These findings improve our understanding of sediment transport under stormy conditions. • Both cold front and typhoon events alter the sediment exchange pattern in the Changjiang Delta. • Typhoon enhances near-bottom sediment resuspension transport from the Changjiang Delta towards the Hangzhou Bay. • Local bed level recovers in a few days from the disturbance caused by extreme events. [ABSTRACT FROM AUTHOR]

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Interactions between a patchy degraded Zostera noltei seagrass meadow and waves, currents, and sedimentary processes were analyzed from data obtained from a strongly wind-influenced micro-tidal brackish water lagoon in southeastern France. Measurements were conducted on offshore and foreshore morphology (topography, bathymetry), on hydrodynamics (waves, water levels, and currents) under different wind conditions within and outside the meadow, and on meadow biometry (shoot density, leaf length). The main impact of this patchy meadow on wind-wave transformations seems to be attenuation of waves further offshore than in the absence of vegetation. This attenuation is particularly notable above the meadow front edge, and is related to wave heights, water levels, and wave periods that are, in turn, dependent on wind intensity and fetch length. The data show that the patchy meadow does not attenuate small and short waves, especially when water levels are high, but is capable, like salt marshes and artificial seagrass, of attenuating relatively high and long waves. Notwithstanding its patchy and degraded character, the meadow also strongly influences the vertical distribution of currents. Whereas currents are strong and significantly influenced by wind and wind waves above the meadow, both waves and currents are dissipated in a transitional canopy-water layer. These wave and current modifications are reflected in the evolution of the seabed. Erosion and sedimentation are mainly controlled by the hydrodynamics but the seasonal state of the meadow plays a role by modulating the hydrodynamics. These substrate changes are, important, in turn, in influencing protection of the shoreline. [ABSTRACT FROM AUTHOR]

Abstract The Pacific Northwest of the United States exhibits complex spatial patterns of storm-induced coastal foredune erosion. Using oceanographic and morphologic data from three field sites encompassing a range of subaqueous and subaerial coastal profile configurations, a relationship is found between morphologic characteristics and dune volume changes during storm events producing high water levels. The data suggest that dune erosion increases with increasing backshore beach slope and that, under particular oceanographic forcing conditions, wave-driven processes can grow the lower portion of dunes on low sloping, dissipative beaches. These observations of environmental and morphologic controls on storm-induced dune impacts are further explored using XBeach, a state of the art numerical model capable of simulating interactions between hydrodynamics and morphology. Consistent with the field data, model simulations indicate that wave-driven dune growth may occur on low sloping beaches in cases where the dynamic still water level (still water level plus wave setup) is lower than the dune toe. However, these accretional processes are restricted to events where limited incident wave energy impacts the dune. Cases with steep backshore beach slopes or dynamic still water levels exceeding the dune toe instead typically result in dune erosion. Additionally, the model simulations suggest that morphologic properties of the shelf, nearshore, and the dune itself influence storm-induced dune volume change. Therefore, morphologic features far from the dune face, including shelf geometries shaped in part by the regional historical sediment budget, may have important implications on the susceptibility of coastal foredunes systems to storm impacts. Highlights • Storm-induced coastal foredune erosion increases with increasing beach slope. • Infragravity swash can contribute positively to dune growth on low sloping beaches. • Total water levels alone are a poor indicator of foredune erosion. [ABSTRACT FROM AUTHOR]

Coastal areas accommodate a great part of large metropolises as they support a great amount of economic and leisure activities. The attraction of people to coastal zones is contributing to an intense and continuous urbanization of these areas, while the ecosystems are threatened by the increase of natural extreme weather events (e.g. intensity and duration of storms, floods), which interfere with local wave climate and changes in morphological beach characteristics. Protection of coastal zones predisposed to coastline recession, due to the action of high tides, high sediment transport deficit, and high wave energy, may involve various coastal structures to reduce or at least to mitigate coastal erosion problems. Many of the current coastal protections (notably groins, seawalls, and emerged breakwaters) were built with a single purpose, which was to protect at all costs without environmental or economic concerns, especially maintenance costs, or the negative consequences that such structures could cause up to considerable distances along the coast. The current concept of integrated coastal zone management presupposes studies involving other types of concerns and more actors in the decision-making process for the implementation of coastal works. In this context, multifunctional structures emerge and are increasingly frequent, such as the so-called multifunctional artificial reefs (MFARs), with the aim of improving leisure, fishing, diving, and other sporting activities, in addition to coastal protection. MFARs are in fact one of the latest concepts for coastal protection. Behind the search for more efficient and sustainable strategies to deal with coastal retreat, this study focused on a comparison between the performance of two traditional coastal protection solutions (submerged detached breakwater and emerged detached breakwater) and an MFAR on a particular coastal stretch. In order to analyse the hydro- (wave height and wave energy dissipation) and morphodynamics (sediment accumulation and erosion areas, and bed level) of the structures and beach interactions, two numerical models were used: SWAN (Simulation WAves Nearshore) for hydrodynamics and XBeach for hydrodynamics and morphodynamics. In addition, a comparison between SWAN and XBeach hydrodynamic results was also performed. From the simulations conducted by SWAN and XBeach, it can be concluded that amongst all structures, the emerged detached breakwater was the most efficient in reducing significant wave heights at a larger scale due to the fact that it constituted a higher obstacle to the incoming waves, and that, regarding both submerged structures (detached breakwater and the MFAR), the MFAR presented a more substantial shadow zone. Regarding morphodynamics, the obtained results presented favourable tendencies to sediment accretion near the shoreline, as well as at the inward areas for the three structures, especially for the emerged detached breakwater and for the MFAR in both wave directions. However, for the west wave direction, along the shoreline, substantial erosion was observed for both structures with more noticeable values for the emerged detached breakwater. For all the northwest wave direction scenarios, no noticeable erosion areas were visible along the shoreline. Overall, considering the balance of erosion and accretion rates, it can be concluded that for both wave predominance, the submerged detached breakwater and the MFAR presented better solutions regarding morphodynamics. The MFAR storm wave condition performed in XBeach indicated substantial erosion areas located around the structure, which added substantial changes in the bed level.

Abstract Past field studies of confluence dynamics have focused mainly on experimental or small stream confluences and confluences of large rivers. Few studies have explored fluvial processes and forms at confluences of medium-size rivers, especially those where river planform varies from a straight alignment. This study examines changes in flow structure, bed morphology, sediment suspension, and mixing with changing incoming flow conditions at a river confluence where a straight tributary joins a curving main channel at the upstream end of a bend. Data include five sets of field measurements of three-dimensional velocity components, bed topography, acoustic backscatter intensity, and water-surface temperatures at the confluence of the curving Wabash River and its straight tributary, the Embarras River. Results show that, in contrast to large river confluences, channel-scale helical motion is a prominent feature of flow structure at this confluence. Dual counter-rotating helical cells, separated by a distinct shear layer, develop over a region of scour within the confluence and contribute to maintenance of scour by sweeping sediment away from this region. Helical motion develops through channel curvature and flow deflection within the confluence. The location and geometry of the scour hole are subject to change depending on the relative momentum fluxes of the two rivers with the zone of scour shifting outward and enlarging as the momentum flux of the tributary increases relative to the momentum flux of the main river. Patterns of backscatter intensity, used here as a surrogate for suspended sediment concentration, confirm that near-bed suspended sediment moves around the scour hole. The thermal mixing interface between the two rivers corresponds to the position of the shear layer, and thermal mixing at the surface within the immediate vicinity of the confluence is limited. The hydrodynamics, morphodynamics, and patterns of sediment suspension and thermal mixing at this river confluence reflect a combination of confluence and bend dynamics. [ABSTRACT FROM AUTHOR]

Abstract The morphodynamics of coastal embayments and estuarine areas are defined by the flow conditions since tidal, wind and wave–induced currents are the main drivers of the sediment transport. In turn, gradients in the resulting sediment transport define sedimentation/erosion patterns and hence the morphodynamic evolution of these systems. Any modification on the average flow conditions, such as those generated by human interventions (i.e. bridge, port constructions or dredging interventions), can be considered as a potential driver inducing morphodynamic changes. This work analyzes the effect of human interventions in estuarine areas and coastal embayments and explores the applicability of tidal asymmetries and residual currents as a proxy for the prediction of the morphodynamic consequences of these interventions. A calibrated and tested numerical model with hydrodynamic and morphodynamic modules is used to compare the variations of tidal asymmetries and residual transport with the bed level evolution in a highly altered bay (Cádiz Bay, Southern Spain). Results show that the future development of the bay will heavily depend on human interventions. The agreement between the morphodynamic tendencies obtained after the analysis of the hydrodynamic variations for the altered scenarios, and the results of the morphodynamic simulations confirms the applicability of the hydrodynamic simulations as a proxy for the morphodynamic evolution. This is of special interest for any other similar coastal embayment or estuary where morphodynamic data are scarce or the calibration of morphodynamic models is too complex. Highlights • Numerical simulations of the hydro-morphodynamics in a highly altered coastal system • Bathymetric scenarios for the different human interventions in the coastal system • Future development of the coastal system heavily depends on human interventions. • Tidal asymmetry and tidal current as a proxy for morphodynamic evolution • Morphodynamic changes caused by alternate periods of flood/ebb dominance [ABSTRACT FROM AUTHOR]

Abstract Deltaic and coastal ecosystems are changing in response to natural and anthropogenic forces that require ecosystem-level restoration efforts to avoid habitat degradation or loss. Models that link ecosystem components of hydrodynamics, morphodynamics, nutrient and vegetation dynamics to represent essential processes and feedbacks are advancing the field of environmental modeling and are vital to inform coastal restoration decisions. An Integrated Biophysical Model was developed by creating a new vegetation dynamics component and linking it to other primary ecosystem components that included essential feedbacks. The model performance was evaluated by applying it to a deltaic ecosystem that included marshes and estuaries. The Integrated Biophysical Model output captured the general temporal and spatial environmental trends of key variables. This integrated model is capable to perform long-term simulations to assess responses of deltaic and coastal systems to global change scenarios and can be used to inform restoration strategies in ecosystems worldwide. Highlights • Development of Delft3D model to assess changing deltaic and coastal ecosystems. • Hydrodynamics, morphodynamics, nutrient and vegetation dynamics were coupled. • Integrated Biophysical Model captured the general environmental trends. • Model is capable to run long-term simulations of environmental conditions. • Software availability. [ABSTRACT FROM AUTHOR]

Abstract Depth-averaged two-dimensional (2D) models are useful tools for understanding river morphodynamics through the computation of hydrodynamics, sediment transport, and an evolving river bed morphology. This paper presents a new parallelized 2D hydrodynamic, sediment transport, and bed morphology model, HydroSedFoam. The model uses the Message Passing Interface for code parallelization and adopts a depth-averaged k − ε turbulence model. Three different case studies, including a laboratory experiment, an analytical solution, and a field-scale river reach, show good agreement with HydroSedFoam simulations. Further development and modification of the model are relatively straightforward to accomplish within the OpenFOAM framework. Highlights • A new parallelized 2D bed morphology model, HydroSedFoam, is developed. • The model shows good parallelization efficiency. • Further development is straightforward to accomplish within the OpenFOAM framework. [ABSTRACT FROM AUTHOR]

Highlights • Introduce sediment-related tidal asymmetry proxy based on skewness method. • Oceanic tides control peak current asymmetry and inter-tidal flats determine slack water asymmetry. • SLR reduces both peak current asymmetry and slack water asymmetry, suggesting a negative feedback mechanism. Abstract Tidal asymmetry in estuaries and lagoons (tidal basins) controls residual sediment transport, and quantifying tidal asymmetry is important for understanding the factors contributing to long-term morphological changes. Asymmetry in peak flood and ebb currents (Peak Current Asymmetry – PCA) controls residual transport of coarse sediment, and asymmetry in slack water duration preceding flood and ebb currents (Slack Water Asymmetry – SWA) controls residual transport of fine sediment. PCA and SWA are analyzed herein for Newport Bay, a tidal embayment in southern California, based on the skewness of tidal currents predicted for several stations by a hydrodynamic model. Use of skewness for tidal asymmetry is relatively new and offers several advantages over a traditional harmonic method including the ability to resolve variability over a wide range of time scales. Newport Bay is externally forced by mixed oceanic tides that are shown to be ebb dominant because of shorter falling tide than rising tide. Both PCA and SWA indicate ebb dominance that favors export of coarse and fine sediments, respectively, to the coastal ocean. However, we show that the ebb dominance of SWA is derived from the basin geometry and not the external forcing, while ebb dominance of PCA is linked to the external forcing and the basin geometry. We also show that tidal flats in Newport Bay play an important role in maintaining ebb dominated transport of both coarse and fine sediments. Loss of tidal flats could weaken PCA and reverse SWA to become flood dominant. Specifically, we show that sea level rise > 0.8 m that inundates tidal flats will begin to weaken ebb dominant PCA and SWA and that sea level rise > 1.0 m will reverse SWA to become flood dominant. This feedback mechanism is likely to be important for predicting long-term evolution of tidal basins under accelerating sea level rise. [ABSTRACT FROM AUTHOR]

Extraction of energy from tidal streams has the potential to impact on the morphodynamics of areas such as sub-tidal sandbanks via alteration of hydrodynamics. Marine sediment transport is forced by both wave and tidal currents. Past work on tidal stream turbine impacts has largely ignored the contribution of waves. Here, a fully coupled hydrodynamic, spectral wave and sediment transport model is used to assess the importance of including waves in simulations of turbine impact on seabed morphodynamics. Assessment of this is important due to the additional expense of including waves in simulations. Focus is given to a sandbank in the Inner Sound of the Pentland Firth. It is found that inclusion of wave action alters hydrodynamics, although extent of alteration is dependant of wave direction. Magnitude of sediment transport is increased when waves are included in the simulations and this has implications for morphological and volumetric changes. Volumetric changes are substantially increased when wave action is included: the impact of including waves is greater than the impact of including tidal stream turbines. Therefore it is recommended that at tidal turbine array sites exposed to large swell or wind-seas, waves should be considered for inclusion in simulations of physical impact. [ABSTRACT FROM AUTHOR]

The hydrodynamics and morphodynamic changes induced by climate change is a serious threat to a coastal community, in which researches are scanty. This study describes how a tropical cyclone and its associated surge, wave and morphological changes would behave in future with persistently changing Representative Concentration Pathway (RCP)-based climate change scenarios. For the prediction of morphodynamics, to fully capture the tidal effects on waves and vice versa, TELEMAC-2D, TOMAWAC and SISYPHE modules are internally coupled with each other. In this study, we considered three scenarios of RCP (4.5, 6.0 and 8.5) in the Near-Future (2025–2045) and Far-Future (2065–2085). To endorse the efficacy of the model in coupled environment, the predicted wind speed, surface elevation and wave climate for an extreme event is compared with the field conditions. The result shows that, in RCP 6.0 and RCP 8.5 in far future, the effects of climate change in terms of maximum wind speed and maximum significant wave height increased in an order of to 10% to 15% and 9% to 14%, respectively. The effect of climate change scenarios in storm surge and current magnitudes does not follow any particular trend. The bed level changes for future scenarios (RCP 6.0 and RCP 8.5) in the area of assessment is doubled from the Control run. The numerical modeling results from this study conveys fresh visions about the effect of tropical cyclone on environmental parameters, in the present and future climate scenarios. [ABSTRACT FROM AUTHOR]

This study presents measurements of sheet flow processes, grain sorting, and bedload plus suspended load transport rates around a medium-sand breaker bar in a large-scale wave flume. The results offer insights in effects of wave breaking on bedload and grain sorting processes and in the quantitative contributions by bedload and suspended transport to breaker bar morphodynamics. Sheet flow layer dynamics are highly similar to observations under non-breaking waves, revealing clear effects by velocity asymmetry but no evident effects by breaking-generated turbulence, bed slope, or the cross-shore non-uniform flow. The sheet flow layer thickness can be predicted using existing empirical formulations based on local hydrodynamic forcing. At locations covering the shoaling region up to the bar crest the cross-shore variation in bedload transport rates is explained by variations in wave shape (i.e. velocity skewness and asymmetry). At locations between bar crest and bar trough, bedload transport rate magnitudes correlate positively with bed slope and turbulent kinetic energy. Bedload and suspended load transport rates are of similar magnitude but of opposite sign. Bedload transport is onshore-directed and dominates in the shoaling zone, but after wave breaking, the offshore-directed suspended sediment transport increases in magnitude and exceeds bedload transport rates in the breaking and inner surf zones. Bedload and suspended load transport contribute notably differently to bed profile evolution: bedload transfers sand grains from the offshore slope to the bar crest and additionally leads to erosion of the shoreward bar slope and deposition at the bar trough, while suspended load transport induces an opposite pattern of erosion at the bar trough and accretion at the bar crest. Grain size analysis of suspended sediment samples reveals size-selective entrainment and vertical size segregation in the inner surf zone, but suggest size-indifferent entrainment and vertical mixing by energetic vortices in the breaking region. Size-selective transport by bedload and suspended load leads to a cross-shore coarsening of the bed from shoaling to inner surf zone, with local additional sorting mechanisms around the breaker bar due to bed slope effects. [ABSTRACT FROM AUTHOR]

Le Bot and Trentesaux (Marine Geology 211, 2004) surveyed the periodic morphological patterns which are present in the English Channel close to the strait of Calais-Dover, where the shortage of sand does not allow the formation of typical sand waves (tidal dunes). The field observations show that, for similar hydrodynamic and morphodynamic conditions, the crest-to-crest distance of the observed sandy mounds is larger than the wavelength of the sand waves which form where sand is abundant. The present contribution describes an idealized model able to predict the hydrodynamics and the morphodynamics of the interaction of tidal currents with large scale bedforms such as sand waves and sandy mounds in sand-starved environments. Indeed, when the availability of sand is limited, classical morphodynamic stability analyses cannot be applied for two main reasons. First, part of the rigid substratum becomes bared when bedforms appear and the bed profile is no longer sinusoidal. Second, the formulae commonly used to quantify sand transport are no longer valid when sandy mounds alternate with a rigid substratum. In accordance with the field observations, the analysis shows that the bedforms which appear when the rigid substratum is bared (sandy mounds) are longer than those which form in a rich sand environment (sand waves). [ABSTRACT FROM AUTHOR]

Fifteen monthly field surveys were conducted from September 2012 to November 2013 at ten representative stations along a cross-shore profile, covering the entire tidal flat. Results indicate that tidal currents significantly affect bed level variations over bare flats, while subsurface processes (e.g., soil subsidence and expansion) are likely to play an important role in changing the bed level of the upper intertidal flat where salt marshes are present. The cross-shore profile shows a clear double-convex shape, and different geomorphic zones display distinctive variation. Above the mean high water level (MHWL), the bed level is generally stable. The region around the MHWL, where the upper convex point is present, is a location of high sedimentation due to the weaker hydrodynamic conditions and the settling and scour lag effects, it keeps growing with the increase of inundation frequency. A concave point occurs in the middle part of the intertidal flat, showing considerable erosion. Near the mean low water level (MLWL), the lower convex point is elevated due to the long-shore tidal current and associated sediment transport (the flood dominated transport during summer exceeds the ebb dominated transport during winter, hence the net effect favors sedimentation). Further seawards, the area below the MLWL is strongly eroded. The cross-shore profile follows a “stable-accretional-erosional-accretional-erosional” sequence. Overall, the measurements indicate that the interplay among vegetation, hydrodynamics and sediment transport is critical in shaping the cross-shore morphology of the intertidal flats along the Jiangsu coast of China. [ABSTRACT FROM AUTHOR]

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The use of numerical models to anticipate the effects of floods and storms in coastal regions is essential to mitigate the damages of these natural disasters. However, local studies require high spatial and temporal resolution numerical models, limiting their use due to the involved high computational costs. This constraint becomes even more critical when these models are used for real-time monitoring and warning systems. Therefore, the objective of this paper was to reduce the computational time of coastal morphodynamic models simulations by implementing a deep learning emulator. The emulator performance was evaluated using different scenarios run with the XBeach software, which considered different grid resolutions and the effects of a storm event in the morphodynamic patterns around a breakwater and a groin. The morphodynamic simulation time was reduced by 23%, and it was identified that the major restriction to reducing the computational cost was the hydrodynamic numerical model simulation. [Display omitted] • The implemented emulator had a high performance in simulating different complex coastal environments. • The transposed convolution layers improved the emulator performance. • A morphodynamic model emulator was developed, reducing the simulation time by 23%. • This emulator, using different input and output numerical model grid resolutions, reduced the simulation time by 86%. • Hydro-morphodynamic results from other numerical models can be used under the proposed methodology. [ABSTRACT FROM AUTHOR]

By utilizing historical satellite image databases, it was possible to assess the rates of coastal retreat in the Grande, Rosario, and Tesoro Islands from 2010 to 2021, due to the influence of climatic variables. It was discovered that the three islands have lost 0.4%, 1.6%, and 9.3% of their landmass, respectively. The notable increase in sea level rise, which has risen 6.2 mm/year since 2010, has emerged as the primary driving factor in the magnitude of erosion by altering the wave transformation patterns in shallow waters. This enables the wave trains to maintain more energy and intensify their height in surf zones, particularly during the dry season, where the wave height has increased by 12%. At the same time, the intensity of longitudinal currents has increased due to the new wave dynamics, leading to changes in the coastlines. Areas characterized by a coastal geomorphology of terraces and beaches, such as Tesoro Island, were found to be the most affected, unlike the cliffs of Grande and Rosario Islands. The study also revealed a lack of policies and concrete actions aimed at mitigating erosion in the coral islands of the Colombian Caribbean. Thus, a set of guidelines is proposed as a starting point to address this issue. [ABSTRACT FROM AUTHOR]

Many deltas, including the Mississippi River Delta, have been losing land at fast rates compromising the safety and sustainability of their ecosystems. Knowledge of delta vulnerability has raised global concern and stimulated active interdisciplinary research as deltas are densely populated landscapes, rich in agriculture, fisheries, oil and gas, and important means for navigation. There are many ways of looking at this problem which all contribute to a deeper understanding of the functioning of coastal systems. One aspect that has been overlooked thus far, yet fundamental for advancing delta science is connectivity , both physical (how different portions of the system interact with each other) as well as conceptual (pathways of process coupling). In this paper, I propose a framework called Delta Connectome for studying connectivity in river deltas based on different representations of a delta as a network. After analyzing the classic network representation as a set of nodes (e.g., bifurcations and junctions or regions with distinct physical or statistical behavior) and links (e.g., channels), I show that from connectivity considerations the delta emerges as a leaky network that continuously exchanges fluxes of matter, energy, and information with its surroundings and evolves over time. I explore each network representation and show through several examples how quantifying connectivity can bring to light aspects of deltaic systems so far unexplored and yet fundamental to understanding system functioning and informing coastal management and restoration. This paper serves both as an introduction to the Delta Connectome framework as well as a review of recent applications of the concepts of network and connectivity to deltaic systems within the Connectome framework. [ABSTRACT FROM AUTHOR]

Sedimentation and erosion can significantly affect the performance of river regulated reservoirs. In the vicinity of flow control structures, the interaction between the hydrodynamics and sediment transport often induces complex morphological processes. It is generally very challenging to accurately predict these morphological processes in real applications. Details are given of the refinement and application of a three-dimensional (3-D) layer integrated model to predict the morphological processes in a river regulated reservoir. The model employs an Alternating Direction Implicit finite difference algorithm to solve the mass, momentum and suspended sediment transport conservation equations, and an explicit finite difference scheme for the bed sediment mass conservation equation for calculating bed level changes. The model is verified against experimental data reported in the literature. It is then applied to a scaled physical model of a regulated reservoir, including the associated intakes and sluice gates, to predict the velocity distributions, sediment transport rates and bed level changes in the vicinity of the hydraulic structures. It is found that the velocity distribution near an intake is non-uniform, resulting in a reduction in the suspended sediment flux through the intake and the formation of a sedimentation zone inside the reservoir. [ABSTRACT FROM AUTHOR]

This paper describes a new, public-domain interface for modeling flow, sediment transport and morphodynamics in rivers and other geophysical flows. The interface is named after the International River Interface Cooperative (iRIC), the group that constructed the interface and many of the current solvers included in iRIC. The interface is entirely free to any user and currently houses thirteen models ranging from simple one-dimensional models through three-dimensional large-eddy simulation models. Solvers are only loosely coupled to the interface so it is straightforward to modify existing solvers or to introduce other solvers into the system. Six of the most widely-used solvers are described in detail including example calculations to serve as an aid for users choosing what approach might be most appropriate for their own applications. The example calculations range from practical computations of bed evolution in natural rivers to highly detailed predictions of the development of small-scale bedforms on an initially flat bed. The remaining solvers are also briefly described. Although the focus of most solvers is coupled flow and morphodynamics, several of the solvers are also specifically aimed at providing flood inundation predictions over large spatial domains. Potential users can download the application, solvers, manuals, and educational materials including detailed tutorials at www.-i-ric.org . The iRIC development group encourages scientists and engineers to use the tool and to consider adding their own methods to the iRIC suite of tools. [ABSTRACT FROM AUTHOR]

Studies on the consequences of dredging on estuarine morphology and its sedimentary dynamics are common, but the impacts of dumping dredge spoil in coastal open settings are rarely found in scientific literature. An experimental study was conducted over the period 2012-2013 to monitor the physical impacts of dredged material dumped at two adjacent sites (one million cubic metres at each) on the inner shelf of the Bay of Seine in France (eastern part of the English Channel, La Manche). As recently reinforced in the EU Marine Strategy Framework Directive (MSFD), knowledge on the location and intensity of human impacts (e.g. on marine ecosystems) is critical for effective marine management and conservation. So, two methods of disposition were tested to evaluate the impacts of dumping on the environment and thus propose recommendations for future dumping. The strategy is based on a Before-After-Control-Impact (BACI) approach, in which the spatio-temporal variability was studied by analysing the morphological and sedimentological characteristics over a period of 28 months, from November 2011 to April 2014, also including recovery of the seafloor after cessation of the dumping activities. The first experimental dumping operation ( MASED ) was carried out regularly for 8 months at a single point and generating a conical deposit of 5 m in height, while the second dumping ( MABIO ) lasted for 12 months involving four steps in the dumping process. In the second case, a wider area was covered, leading to the formation of a smaller deposit of 2 m in height. The dumped deposits consisted of muddy fine sand, whereas the inner shelf seafloor in this area is covered with fine to medium sand. As a result, muddy fine sand accumulated at or near the two dumping sites, with a maximum mud (i.e. particles<63 μm or>4 Φ) content of 50% compared to<5% before dumping operations. Videos obtained from a LVB200 Seabotix ROV, highlighted the heterogeneity of the sea floor around the dumping areas. Due to hydrodynamic forcing (wave climate and tidal currents), about 50% ( MABIO ) and 75% ( MASED ) of the volume of dredged material remained at the end of the dumping periods. After dumping ceased, a further 5% of material for MABIO and 20% for MASED, was transported out of the study area. For the latter, a spreading of fine particles was observed extending from the conical deposit towards the south west. To favour long-term exploitation, a more dispersive dumping over a wider surface area is recommended (e.g. MABIO) [ABSTRACT FROM AUTHOR]

Ripple bedform response to near bed forcing has been found to be asynchronous with rapidly changing hydrodynamic conditions. Recent models have attempted to account for this time variance through the introduction of a time offset between hydrodynamic forcing and seabed response with varying success. While focusing on temporal ripple evolution, spatial ripple variation has been partly neglected. With the fingerprint algorithm ripple bedform parameterization technique, spatial variation can be quickly and precisely characterized, and as such, this method is particularly useful for evaluation of ripple model spatio-temporal validity. Using time-series hydrodynamic data and synoptic acoustic imagery collected at an inner continental shelf site, this study compares an adapted time-varying ripple geometric model to observed field observations in light of the fingerprint algorithm results. Multiple equilibrium ripple predictors are tested within the time-varying model, with the algorithm results serving as the baseline geometric values. Results indicate that ripple bedforms, in the presence of rapidly changing high-energy conditions, reorganize at a slower rate than predicted by the models. Relict ripples were found to be near peak-forcing wavelengths after rapidly decaying storm events, and still present after months of sub-critical flow conditions. [ABSTRACT FROM AUTHOR]

Coastal and shoreline management increasingly needs to consider morphological change occurring at decadal to centennial timescales, especially that related to climate change and sea-level rise. This requires the development of morphological models operating at a mesoscale, defined by time and length scales of the order 10 1 to 10 2 years and 10 1 to 10 2 km. So-called ‘reduced complexity’ models that represent critical processes at scales not much smaller than the primary scale of interest, and are regulated by capturing the critical feedbacks that govern landform behaviour, are proving effective as a means of exploring emergent coastal behaviour at a landscape scale. Such models tend to be computationally efficient and are thus easily applied within a probabilistic framework. At the same time, reductionist models, built upon a more detailed description of hydrodynamic and sediment transport processes, are capable of application at increasingly broad spatial and temporal scales. More qualitative modelling approaches are also emerging that can guide the development and deployment of quantitative models, and these can be supplemented by varied data-driven modelling approaches that can achieve new explanatory insights from observational datasets. Such disparate approaches have hitherto been pursued largely in isolation by mutually exclusive modelling communities. Brought together, they have the potential to facilitate a step change in our ability to simulate the evolution of coastal morphology at scales that are most relevant to managing erosion and flood risk. Here, we advocate and outline a new integrated modelling framework that deploys coupled mesoscale reduced complexity models, reductionist coastal area models, data-driven approaches, and qualitative conceptual models. Integration of these heterogeneous approaches gives rise to model compositions that can potentially resolve decadal- to centennial-scale behaviour of diverse coupled open coast, estuary and inner shelf settings. This vision is illustrated through an idealised composition of models for a ~ 70 km stretch of the Suffolk coast, eastern England. A key advantage of model linking is that it allows a wide range of real-world situations to be simulated from a small set of model components. However, this process involves more than just the development of software that allows for flexible model coupling. The compatibility of radically different modelling assumptions remains to be carefully assessed and testing as well as evaluating uncertainties of models in composition are areas that require further attention. [ABSTRACT FROM AUTHOR]

Brambilla, W.; van Rooijen, A.; Simeone, S.; Ibba, a.; DeMuro, S., 2016. Field observations, coastal video monitoring and numerical modeling of coastal processes at Poetto Beach, Italy. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 825-829. Coconut Creek (Florida), ISSN 0749-0208. This work presents an analysis of hydrodynamics and morphological evolution during one year at Poetto Beach (South Sardinia, Gulf of Cagliari - Italy). The results, in the form of a numerical model, Delft3D, were validated using data obtained from a very reproducible low-cost video monitoring system. Subsequently, the model was used to study local hydrodynamics (Delft3D) during wave events. Poetto Beach is a wave-dominated urban beach system characterized by an inner shelf with Posidonia oceanica meadows. Bathymetric and topographic surveys were carried out every three months in order to understand the beach morphology. Sediment grain samples were taken alongshore/cross-shore in correspondence with the main morphologies. The Delft3D model was used to simulate waves and hydrodynamics. The numerical simulation (Delft3D) showed good agreement with the field data and video image analyses for the distribution and direction of the rip and longshore currents. This approach, which can be easily replicated on other urban beaches, could provide beach managers with useful information on how to prevent and minimize the effects of storms and flooding. [ABSTRACT FROM AUTHOR]

We develop a consolidation module and merge it into a morphodynamic model to assess the role of consolidation on estuarine morphodynamics. We test the model using two settings: point models without hydrodynamic forcing to validate against two benchmark experimental datasets; and a profile model to simulate a mudflat restoration. The modelled self-weight consolidation influences the simulations by gradually reducing the bed level and decreasing the bed erodibility (i.e., increasing the critical bed shear stress). Both effects modify sediment transport processes on mudflats, leading to long-term morphodynamic effects. Depending on the initial bathymetry, the hydrodynamic forcing and the soil properties, the simulated morphological change of the restored mudflat may differ considerably with and without considering consolidation. The consolidation model developed can be utilised to assess the medium to long term effects related to estuarine development (e.g., wetland restoration) and aims to be a publicly available tool. [ABSTRACT FROM AUTHOR]