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This study aims to assess shoreline change rates at al-Gamil Beach, west of Port Said City on the northeastern Mediterranean coast of Egypt. The study area is characterized by two main tidal inlets connected Lake EL-Manzala by the sea and other coastal protection structures. Given that the al-Gamil coastline shall be monitored to explore erosion and sedimentation changes along the shoreline, multi-temporal satellite images and an ArcGIS-based DSAS model application were utilized to identify and measure changes to the coastline. Five Landsat images covering the study area were used to identify patterns of coastline accretion and erosion. These images were corrected geometrically and radiometrically to help the investigation process of coastline change rates. The three DSAS statistical models: Linear Regression Rate, End Point Rate, and Net Shoreline Movement were used to assess the shoreline change rate. Based on these findings, the shoreline has alternate exposure to accretion and erosion at varying rates, where the average rate of accretion is nearly +9 m/year, while the maximum rate of erosion is about −27 m/year. [ABSTRACT FROM AUTHOR]

The temporal and spatial scales controlling the morphodynamics of barrier-inlet systems are critical components of regional sediment management practice. This paper discusses regional sediment management methods employed at multiple barrier-inlet systems, with case studies from West-Central Florida. A decision-support tool is proposed for regional sediment management with discussion of its application to barrier-inlet systems. Connecting multiple barrier islands and inlets at appropriate spatio-temporal scales is critical in developing an appropriately scoped sediment management plan for a barrier-inlet system. Evaluating sediment bypassing capacity and overall inlet morphodynamics can better inform regional sand sharing along barrier-inlet coastlines; particularly where sediment resources are scarce and a close coupling between inlet dredging and beach placement is vital to long-term sustainable management. Continued sea-level rise and anthropogenic activities may intensify the need for investigating longer-term processes and expanding regional planning at a centennial timescale, and are acknowledged as challenging tasks for RSM studies. Specifically, we suggested that a regionally focused, multi-inlet study were necessary for management plan of individual inlet for the west-central Florida case studies. Key recommendations based on the case studies include: 1) allow the natural sediment bypassing to be re-established at Blind Pass inlet through reduced ebb-tidal delta mining, 2) reduce the interruption to sediment bypassing at John's Pass and Pass-a-Grille inlets through an improved design of the dredged mining areas located along sediment bypassing pathways, 3) allow for continued natural sediment bypassing at Bunces Pass, and, 4) incorporate the cyclic swash-bar attachment sediment bypassing into the management plan at Bunces Pass and adjacent barrier-islands. • This paper discusses regional sediment management methods employed at multiple barrier-inlet systems. • A decision support tool is proposed for regional sediment management with application in barrier-inlet systems. • Evaluating sediment bypassing capacity with inlet morphodynamics can better inform regional sand sharing. [ABSTRACT FROM AUTHOR]

Abstract Alterations to the tidal inlets shoals, whether natural or anthropogenic, can dramatically influence the hydro-morphological balance of the inlet system in the short and long-term. Jettied inlets, despite typically supported by former technical design reports in curtailing the sedimentology stock, sometimes they require amendments. This paper provides an expository epitome for understanding the role of jetties in concerning the extent of their adequacy to economically and ecologically rationalize the internal siltation within both the western and the eastern tidal inlets of the Bardawil Lagoon, which is situated along the Mediterranean coastline of the Sinai Peninsula, Egypt. The main tool to characterize that role is the hydro-morphological modeling of the inlets system. We used a two-dimensional hydrodynamic circulation model consisting of two steering modules, CMS-Flow and CMS-Wave. In a five-year simulation process, this study emphasized that the sole use of jetties was noticeably insufficient to fulfill the satisfactory stabilization of the sedimentation processes inside the inlets. Consequently, the lake's ecosystem might entirely collapse in the short run due to the progressive deposits fashioning in the form of ebb/flood-tidal deltas. Accordingly, we proposed alternative solutions based on structural modulation scenarios in the vicinity of inlets domain encompassing jetties extension, flow-diverted wall (FDW), sediment trap (ST), random radial channels (RC) and lateral wide channel (LWC). Based upon the results of an optimization model using the Mamdani-type fuzzy inference system, the addition of a lined LWC alongside with jetties proved to be an effective solution over a longer period that rather meets the needs of the majority of stakeholders satisfactorily. [ABSTRACT FROM AUTHOR]

Abstract Quarter-diurnal tidal constituents are linked to tidal asymmetries and play a role in the morphodynamic evolution of inlets, estuaries and lagoons. A two-year non-continuous dataset of current velocities and waves was used to improve understanding on the generation of quarter-diurnal harmonics. Data analysis provides evidence for the generation of quarter-diurnal harmonics by wind-induced waves. Data were collected at the entrance to the Arcachon Lagoon, a mixed-energy tidal inlet in Southwest France. Temporal variability of the quarter-diurnal tidal current was identified through wavelet analysis of the main velocity component (alongshore velocity). Quarter-diurnal velocity amplitudes, bottom and wave stresses, and significant wave height suggested a linkage between quarter-diurnal amplification and wave action. Both significant wave height and wave stress were coherent with quarter-diurnal current amplitudes at synoptic frequencies, most markedly in winter months of both years observed. These coherences corroborated the hypothesis that wind-induced waves enhance bottom stresses that can generate and augment quarter-diurnal currents in this region. Highlights • Current velocities and waves recorded in a mixed-energy tidal inlet are analyzed. • Occurrence of quarter-diurnal overtide current amplitudes higher than semidiurnal ones. • Mechanisms outside tidal forces contribute to overtide generation in this region. • A linkage between quarter-diurnal currents and wave action is suggested. • Quarter-diurnal D 4 can be generated by wind-induced waves at synoptic periodicity. [ABSTRACT FROM AUTHOR]

A network of cross-shelf paleovalleys has been recognized over the paleo-inner shelf off the Gilão-Almargem Estuary, a small fluvial drainage system that presently receives minor sediment supply in the eastern Algarve shelf, northern margin of the Gulf of Cadiz (SW Iberian Peninsula). This study is aimed at determining the driving controls that triggered substantially different paleohydrological conditions and sedimentary dynamics of ancient fluvial systems in this margin. We focus on evidences of secondary controls on valley genesis and evolution, superimposed to primary glacio-eustatic control such as antecedent geology, low fluvial supply and changing hydrodynamic regimes. The architecture and spatial distribution of these paleovalleys were interpreted based on a grid of seismic profiles with different resolutions. Likewise, a sediment core obtained in a distal position of the paleovalley system provided information about sedimentary processes during the most recent stage of valley infilling. The chronostratigraphic framework was constructed based on regional seismic horizons defined in previous studies and complemented with two AMS 14C dates obtained from bivalve shells. The inner shelf paleovalley system is composed of several incised valley features which exhibit a remarkable similar internal architecture. These inner valley features exhibit two major incision phases (from oldest to youngest; IP 2 and IP 1) that are thought to constitute a simple paleovalley system formed during the last glacial cycle. The origins of the incision are considered to be different. The older one is related to fluvial incision during the sea-level fall leading into the Last Glacial Maximum, whereas the recent one is interpreted as the result of tidal scour during the postglacial transgression. Their corresponding infillings are interpreted, respectively, as estuarine bay-fill deposits and estuary-mouth sands. Overlying the paleovalley infilling, a distinctive reflective unit is in agreement with the generation of coastal barriers and related depositional systems. The formation of the paleo-inner-shelf paleovalley system was strongly conditioned by antecedent geology, which strongly limited the generation of wide incised valleys and determined the amount of incision landward of a well-defined break of slope. Its postglacial infilling was mainly estuarine in nature, likely involving the development of a dendritic system, with numerous barriers interrupted by tidal inlets and channels in a mixed estuarine system with low fluvial supply. • Inner-shelf valleys interpreted as a simple system formed during the last glacial cycle. • The valleys infilling records the occurrence of wave- and tide-dominated processes. • Incised valley formation was strongly determined by antecedent geology. • The infilling took place under high rates of sea-level rise and low fluvial supply. • The system comprised an estuarine system with multiple barriers and inlets. [ABSTRACT FROM AUTHOR]

The authors have shown previously that over very long time scales a barrier estuary or tidal inlet will tend towards one of two states, called attractors. In this paper it is shown how that analysis represents an extension and generalisation of three earlier procedures. There are three widely recognised quantitative semi-empirical procedures describing the long term equilibrium dimensions of the entrance channel of barrier estuaries and tidal inlets. The best known of these laws is the tidal prism-entrance area relation, often referred to as the O'Brien equation. The second procedure is based on the Escoffier or closure diagram, comprising a simple hydrodynamic relationship between the entrance area and the entrance velocity together with an empirical "equilibrium velocity". The third is the set of rules developed by Bruun that relate the entrance channel stability to the longshore sediment supply and the entrance channel sediment transport capacity. Each of these is based on major simplifications that restrict its utility and range of validity more than is usually recognised. The attractor analysis, while still based on a lumped model, adds sediment transport and deposition/scour equations and enables the use of more realistic entrance hydrodynamics. It predicts the rates of change and presents the results on a practical “attractor map”. The predictions of the three empirical laws are compared with the attractor map and their practical application is critically compared. The empirical laws are shown to provide broadly equivalent predictions to the attractor map, but over limited ranges of estuary conditions. In particular, none of the empirical laws identifies the entrance closure state or describes conditions near closure. [ABSTRACT FROM AUTHOR]

Climate change (CC) is likely to affect the thousands of bar-built or barrier estuaries (here referred to as Small tidal inlets - STIs) around the world. Any such CC impacts on the stability of STIs, which governs the dynamics of STIs as well as that of the inlet-adjacent coastline, can result in significant socio-economic consequences due to the heavy human utilisation of these systems and their surrounds. This article demonstrates the application of a process based snap-shot modelling approach, using the coastal morphodynamic model Delft3D , to 3 case study sites representing the 3 main STI types; Permanently open, locationally stable inlets (Type 1), Permanently open, alongshore migrating inlets (Type 2) and Seasonally/Intermittently open, locationally stable inlets (Type 3). The 3 case study sites (Negombo lagoon – Type 1, Kalutara lagoon – Type 2, and Maha Oya river – Type 3) are all located along the southwest coast of Sri Lanka. After successful hydrodynamic and morphodynamic model validation at the 3 case study sites, CC impact assessment are undertaken for a high end greenhouse gas emission scenario. Future CC modified wave and riverflow conditions are derived from a regional scale application of spectral wave models (WaveWatch III and SWAN) and catchment scale applications of a hydrologic model (CLSM) respectively, both of which are forced with IPCC Global Climate Model output dynamically downscaled to ~ 50 km resolution over the study area with the stretched grid Conformal Cubic Atmospheric Model CCAM. Results show that while all 3 case study STIs will experience significant CC driven variations in their level of stability, none of them will change Type by the year 2100. Specifically, the level of stability of the Type 1 inlet will decrease from ‘Good’ to ‘Fair to poor’ by 2100, while the level of (locational) stability of the Type 2 inlet will also decrease with a doubling of the annual migration distance. Conversely, the stability of the Type 3 inlet will increase, with the time till inlet closure increasing by ~ 75%. The main contributor to the overall CC effect on the stability of all 3 STIs is CC driven variations in wave conditions and resulting changes in longshore sediment transport; not Sea level rise as commonly believed. [ABSTRACT FROM AUTHOR]

Numerical models of ocean circulation often depend on parameters that must be tuned to match either results from laboratory experiments or field observations. This study demonstrates that an initial, suboptimal estimate of a parameter in a model of a small bay can be improved by assimilating observations of trajectories of passive drifters. The parameter of interest is the Manning’s n coefficient of friction in a small inlet of the bay, which had been tuned to match velocity observations from 2011. In 2013, the geometry of the inlet had changed, and the friction parameter was no longer optimal. Results from synthetic experiments demonstrate that assimilation of drifter trajectories improves the estimate of n , both when the drifters are located in the same region as the parameter of interest and when the drifters are located in a different region of the bay. Real drifter trajectories from field experiments in 2013 also are assimilated, and results are compared with velocity observations. When the real drifters are located away from the region of interest, the results depend on the time interval (with respect to the full available trajectories) over which assimilation is performed. When the drifters are in the same region as the parameter of interest, the value of n estimated with assimilation yields improved estimates of velocity throughout the bay. [ABSTRACT FROM AUTHOR]

• The papers in this VSI describe major results from the Coastal Genesis 2 research programme in the Netherlands. • Coastal Genesis 2 aimed at the development of a future-proof long-term coastal management strategy. • Three types of papers are included: policy development, lower shoreface, and Wadden Sea tidal inlet systems. [ABSTRACT FROM AUTHOR]

Ebb-tidal deltas are bulges of sand that are located seaward of tidal inlets. Many of these deltas feature shoals that cyclically form and migrate towards the coast. The average period between successive shoals that attach to the coast varies among different inlets. In this study, a quantitative assessment of the cyclic behavior of shoals on the ebb-tidal deltas of the Wadden Sea is presented. Analysis of bathymetric data and Landsat satellite images revealed that at the majority of inlets along the Wadden Sea migrating shoals occur. The average period between succeeding shoals correlates to the tidal prism and has values ranging between 4 and 130 years. A larger tidal prism favors larger periods between successive shoal attachments. However, such a relationship was not found for wide inlets with multiple channels. There is a positive relationship between the frequency with which the shoals attach to the coast and their migration velocity, and a negative relationship between the migration velocity of the shoal and the tidal prism. Finally, the data were too sparse to assess whether the longshore sediment transport has a significant effect on the period between successive shoals that attach to the coasts downdrift of the observed tidal inlets. [ABSTRACT FROM AUTHOR]

Coastal zones in the vicinity of tidal inlets are commonly utilised for navigation, fishing, sand mining, waterfront development and recreation and are under very high population pressure. Any negative impacts of climate change (CC) on inlet environment are therefore very likely to result in significant socio-economic impacts. CC driven variations in mean water level (i.e. SLR), wave conditions and riverflow are likely to affect the stability of, particularly, the thousands of Small Tidal Inlets (STIs, or bar-built/barrier estuary systems) around the world. The combination of their predominant occurrence in developing countries, socio-economic relevance and low community resilience, general lack of data, and high sensitivity to seasonal forcing makes STIs potentially very vulnerable to CC impacts. This article summarises potential CC impacts on the stability of STIs and discusses means by which these CC impacts maybe quantified using existing modelling tools. As presently available process based models cannot be confidently applied with concurrent time varying water level, wave and riverflow forcing over typical CC impact assessment time scales (~ 100 years), a ‘snap-shot’ simulation (~ 1 year duration) approach using process based coastal area morphodyamic models is proposed for qualitative assessments of CC impacts on STIs. As the modelling approach will by necessity depend on the level of data availability, two different ‘snap-shot’ modelling frameworks for ‘data rich’ and ‘data poor’ environments are presented. Process based multi-scale coastal area morphodynamic models and scale aggregated (or reduced complexity) morphodynamic models are identified as modelling approaches that may be pursued in the future to obtain more reliable assessments of CC impacts on STI stability. [ABSTRACT FROM AUTHOR]

Coastal inlets are the openings along the coastline that provide a linkage between the open ocean and the hinterland water bodies. These coastal inlets are varied in nature depending on many influencing parameters such as tide, wind, river flow and waves. Amongst these parameters, the tides are the most regular while waves and freshwater flow are more seasonal. The tidal inlets have to be examined and studied to understand the nearshore coastal processes. The inlet remains stable (i.e. open) as long as the alongshore sediment bypasses the tidal inlet. Classification of coastal systems in a broader view is necessary for the management of tidal inlets. There are several methods to classify tidal inlets based on different perspectives namely geo-morphological, hydrodynamic etc. In the present study, tidal inlet classification is carried out considering the hydrodynamics and morphodynamics along the Andhra Pradesh coast, considering the classification method as in Hayes (1984) and Thuy (2013). The Hayes (1984) classification considers only the tidal range and significant wave height, whereas Thuy (2013) considers discharge due to tide (∼Tidal prism /tide duration) and wave (∼ ). A total of 108 tidal inlets along Andhra Pradesh coast on the east coast of India are classified considering annual mean wave height (Hs) as well as seasonal wave heights. This paper presents the methods used and results of the coastal classification along the central east coast of India. [ABSTRACT FROM AUTHOR]

Abstract: Pulicat is India׳s second largest brackish water lagoon with its mouth opening in the Bay of Bengal. The dynamics of the tidal inlet at Pulicat has been reported in this study on the basis of long term analysis using satellite remote sensing aided with Geographical Information System (GIS) and berm crest data. In addition, the short term analysis was carried out using monthly in situ Global Positioning System (GPS) profiling and sediment grain size analysis. The study of the shoreline dynamics along the inlet using the Linear Imaging Self – Scanning Sensor (LISS) – III along with the Survey of India toposheet of 1954 reveals that the inlet once with a single mouth is divided into two, over the period of time with the southern mouth migrating towards north with an inconsistent migration pattern of the northern mouth. The overall extent of migration is found to be within 3km. The outcome of the 25 year berm crest data starting from 1978 revealed the coastline around Pulicat is eroding upto 1990 and thereafter it is accreting with the net shoreline erosion rate of 20.34m/yr. The monthly in situ beach profiling studies from August 2004 to July 2005 revealed that the Pulicat inlet follows a variable migratory pattern with a shift of upto 914m North during August to December with a reversal migration of 600m thus leading to a net migration towards the north. The grain size analysis has unravelled the sediment transport around Pulicat inlet. The study of the inlet using satellite imagery during monsoon has clearly justified the dominant fresh water inflow regulatory force over the tidal forces and the positive influence of the Tsunami on opening the inlet during monsoon failure. [Copyright &y& Elsevier]

For successful and sustainable management of barrier islands, a thorough understanding of the ebb-tidal delta dynamics and interactions with the adjacent shorelines are of the utmost importance. Such understanding requires detailed observations and interpretations of the morphodynamics of smaller-scale features such as the individual channels and shoals (referred to as intra-delta dynamics). The intra-delta dynamics of Ameland Inlet (the Netherlands) are studied through analysis of sixteen high-resolution bathymetric surveys, supplemented with an extensive dataset of hydrodynamic observations collected in 2017. The observations are compiled into a synthesis of the morphodynamics of the ebb-tidal delta and its neighboring shorelines, to provide a basis for present day and future coastal management. Our observations show that Ameland Inlet as a whole can be classified as a typical mixed-energy, wave-dominated system. However, the ebb-tidal delta contains distinct areas that are wave or tide dominated, and these areas evolve with the changing morphodynamics of the ebb delta. Between 2005 and 2021, large morphodynamic changes have occurred on the ebb-tidal delta and continuous erosion of the island tips occurred. Limited wave-sheltering by the ebb-tidal delta exposes the shorelines of the adjacent barrier islands to significant wave-driven sand transports and sand losses. Sediment supply from longshore transport and the erosion of the updrift island Terschelling contributed to the formation, growth and migration of a series of ebb-chutes and lobes, which eventually led to complete relocation of the main channel on the ebb-tidal delta. This main channel relocation took 15 years to complete and is an example of the ebb-delta breaching model of sand bypassing. Changes in the sediment bypassing patterns result in a sediment starved western island tip of Ameland, necessitating repeated sand nourishments under the Dutch coastal maintenance policy. Our observations also confirm the role the ebb-tidal delta as a sand reservoir for the downdrift barrier island. The delta sand body is not a reservoir for the back-barrier basin, since the basin is predominantly supplied with sand eroded from the updrift island of Terschelling. As demonstrated in this study, the intra-delta dynamics of an ebb-tidal delta are complex and can change drastically through time. Only through detailed measurements and observations can all the intricate interactions that take place be unravelled. • Morphodynamics of Ameland Inlet ebb-tidal delta investigated based on extensive and detailed observations. • Understanding the complex and variable intra-delta dynamics is essential for coastline management. • Ebb-tidal delta breaching at Ameland Inlet occurs on a 15-year timescale. • Limited wave-sheltering and sediment-bypassing variations induce island tip erosion. [ABSTRACT FROM AUTHOR]

River deltas and enclosed lagoons represent a zone where fluvial and littoral processes interact through the redistribution, erosion, and deposition of sediment, which have a large impact on coastal management and engineering. The focus of the study is to understand the correct balance between strategies that maintain the navigational efficiency of tidal inlets and those that respect the ecological and economical functions of coastal lagoons. We applied an integrated modeling system that links multiple hydrodynamic and morphodynamic models to understand how coastal processes and associated sediment transport influences the functioning of the southern inlet of the Barbamarco Lagoon in the Po River Delta, Italy. Moreover, our study provides engineering solutions to improve the inlet functioning efficiency and a proposal for a monitoring plan. Our results highlight the importance of the seasonal effects of wave climate on the littoral sediment transport. Model outcomes show that the dredging volume is approximately 15,000 cubic meter/year for the southern inlet, which may vary with wave climate. However, creating a wider seaward tidal channel will reduce dredging activities over a longer interval than would sediment removal. A deeper and wider channel will deflect the along shore current seaward and cause sediment to bypass the inlet. Therefore, the sediment will reach the erosional side of the inlet and enhance the redistribution of the sediment, which may reduce over wash during storms and high-water levels. Our results illustrate the ephemeral equilibrium of tidal inlets and coastal lagoons in deltaic systems impacted by large riverine sediment delivery. Shore management scenarios and decisions rely on hydro-morphodynamic numerical models that predict best practices for coastal sustainability. [ABSTRACT FROM AUTHOR]

Abstract: The morphodynamics of the John''s Pass–Blind Pass dual inlet system were investigated based on hydrodynamic and morphology measurements, and numerical modeling. The co-existence of the dual inlets is realized by the dominance of mixed-energy John''s Pass in terms of tidal prism and size of the ebb delta and the artificial maintenance of the wave-dominated migratory Blind Pass. Due to the secondary role of Blind Pass, the aggressive anthropogenic activities there do not seem to have a significant influence on the morphodynamics of John''s Pass. On the other hand, the opening (in 1848) and subsequent evolution of John''s Pass had substantial influence on Blind Pass, causing it to migrate rapidly to the south. In addition, anthropogenic activities had much more influence on the morphodynamics of the secondary Blind Pass than that of the dominating John''s Pass. Results from numerical modeling provide a semi-quantitative understanding of the hydrodynamics and morphodynamics of John''s Pass and Blind Pass in association with cold front passages, which have substantial influences on inlet morphology. Two large eddies are modeled from the interactions between the southward longshore current and John''s Pass ebb and flood flow, respectively. These eddies are closely related to the morphodynamics of the channel margin linear bar and longshore transport divergence at the downdrift side. Both are key features of a mixed-energy inlet. The shallow water and wave-breaking-induced longshore current and elevated sediment suspension along the ebb delta terminal lobe provide the pathway for sediment bypassing. The morphodynamics of Blind Pass are dominated by wave forcing. The weak ebb jet is not capable of forming a sizable ebb delta and tends to be deflected by the strong longshore current, causing elevated longshore transport along the downdrift beach. The 90-degree turn of the inlet, which is common for wave-dominated migratory inlets, results in weak ebb flushing along the updrift (north) side of the inlet, and is responsible for the alongshore migration of the inlet before the artificial stabilization and sedimentation along the northern side of the inlet following stabilization. [Copyright &y& Elsevier]

Abstract: Details are given herein of the refinement and application of a three-dimensional layer integrated numerical model to predict morphological changes in tidal basins. The solution of governing differential equations, which consist of the conservation of mass and momentum for the hydrodynamics, the transport equation for the suspended sediment fluxes and the sediment mass conservation equation for the bed level changes are carried out by the use of Alternating Direction Implicit (ADI) Finite Difference Method (FDM). The model includes different criteria for the initiation of motion namely Shields (1936, Application of Similarity Principles and Turbulence Research to Bed load Movement, Hydrodynamics Laboratory, California Institute of Technology, Pub. No. 167), Kolahdoozan (1999, Numerical Modelling of Geomorphological Processes in Estuarine Waters, PhD Thesis, Department of Civil and Environmental Engineering, University of Bradford, Bradford, UK, 288) and Zanke (2003, On the Influence of Turbulence on the Initiation of Sediment Motion, International Journal of Sediment Research, 18(1), 17–31), to compare different aspects of flow conditions. As the flow is highly turbulent with the random nature of its components, many researchers have tried to express sediment transport processes by using stochastic approaches. In the current study both deterministic and stochastic methods are included in the numerical model to evaluate their accuracy and efficiency. To validate the numerical model results, laboratory measurements are used, with these being obtained from an earlier experimental program undertaken by the authors. Results of a short term bed level changes in a laboratory model harbor are included for the model verification purposes. Comparisons are undertaken using different criteria for the initiation of motion, with the results highlighting that the unsteadiness in the flow parameters included in the numerical model has a major effect on the bed level changes inside the harbor, in compare with the turbulence structure of the flow. The model is then applied to a real case study of the Humber Estuary, located in the UK, with comparisons being undertaken for different criteria for the initiation of motion, using both deterministic and stochastic approaches for the long term bed level predictions. [Copyright &y& Elsevier]

Abstract: Month-long observations of waves and tidal currents at Ponce de Leon Inlet, North Florida are used to investigate the importance of wave-induced bottom drag as a mechanism for overtide generation in estuaries. While bottom drag can in theory lead to overtide generation, in practice, resolving unambiguously this effect is difficult as it tends to be overshadowed by the stronger effect of diurnal–semidiurnal tidal variance. Bottom boundary layer numerical simulations based on observational data suggest that waves can cause the bottom drag experienced by currents to increase by a factor of 1.7, compared with relatively calm conditions. Despite the relatively short duration and limited scope of the experiment, the analysis suggests that overtide modulations (East–West velocity components of the 5th and 6th diurnal constituents) are correlated with wave-enhanced drag trends. Therefore, wave-enhanced bottom drags may be enhancing generation of overtides. Further work is necessary to understand the scope and the strength of this mechanism, in relation to the characteristics (e.g., flow direction) of individual overtides. [Copyright &y& Elsevier]

Abstract: Although it is generally acknowledged that most multiple inlets are unstable and cannot coexist, there is evidence to suggest that such inlets can indeed be stable over decadal time scales. Multiple-inlet systems servicing a single embayment, in contrast to single-inlet systems, confer particular hydrodynamic characteristics such as the potential existence of residual discharges and currents between the inlets. This paper presents detailed measurements of hydrodynamic variables obtained over complete spring and neap tidal cycles in a multiple-inlet system in Southern Portugal (Ria Formosa). The results indicate that the two main interconnected inlets servicing an embayment can coexist, at least over a time scale of several decades. However, their coexistence cannot be explained simply using empirical equilibrium relations or inlet hydraulics. Although residual flow between the inlets appears to play an important role enhancing their stability, it is the availability of sediment stored in the ebb-tidal deltas (and its capacity to be carried into the inlets during storm events) that ultimately dictates the overall equilibrium, independently of the flushing capability provided by the hydraulics. Such movement of sediment leads to the obstruction of the inlet channels, thereby affecting the hydraulic efficiency and eventually leading to inlet closure in the long term. The results augment existing knowledge concerning multiple-inlet systems and improve understanding of their short- to medium-term stability. [Copyright &y& Elsevier]

Abstract: This paper presents results of recent measurements of sand transport made in Chioggia inlet as part of an extensive monitoring programme in the Venetian inlets. Measurements were made in order: (1) to define a relationship between sand transport magnitude and tidal flow; (2) to derive the thresholds for sand transport; (3) to identify the dominant modes of transport; (4) to evaluate the concentration profiles of sand within the benthic boundary layer; (5) to compare bedload transport observations with model predictions using existent bedload formulae; and (6) to produce yearly estimates of bedload transport across the inlet. The vertical distribution of sand in the water column was sampled using modified Helley–Smith bedload samplers at three sites. Transport was found to vary according to the flow and bed grain size, with considerable temporal and spatial variability. A difference of up to three orders of magnitude in transport was observed through the inlet, with higher transport rates measured on the seaward part. The dominant mode of transport in the central inlet was suspension, while bedload was dominant in the mouths. The measured profiles of sand concentration varied with the tidal stage and seabed grain size according to the Rouse parameter (R). R was high at the inlet mouths (1

Abstract: To describe the exchange of water and sediment through the Venice Lagoon inlets a 3-D hydrodynamic and sediment transport model has been developed and applied to a domain comprising Venice Lagoon and a part of the Adriatic Sea. The model has been validated for both current velocities and suspended particle concentration against direct observations and from observations empirically derived fluxes from upward-looking acoustic Doppler current profiler probes installed inside each inlet. The model provides estimates of the suspended sediment transport in the lower 3m of the water column that is not detected by acoustic Doppler current profiler sensors. The bedload model prediction has been validated against measured sand transport rates collected by sand traps deployed in the Lido and Chioggia inlets. Results indicate that, in the Lido inlet, 87% of the total load is in suspension, while the rest moves as bedload. [Copyright &y& Elsevier]

Abstract: In this paper the wind-wave variability in the tidal basins of the German Wadden Sea is modelled with combined numerical and neural-network (NN) methods. First, the wave propagation and transformation in the study area are modelled with the state-of-the-art third-generation spectral wave model SWAN. The ability of SWAN to accurately reproduce the phenomena of interest in nonstationary conditions governed by highly variable winds, water levels and currents is shown by comparisons of the modelled and measured mean wave parameters at four stations. The principal component analysis of the SWAN results is then used to reveal the dominating spatial patterns in the data and to reduce their dimensionality, thus enabling an efficient and relatively straightforward NN modelling of mean wave parameters in the whole study area. It is shown that the data produced with the approach developed in this work have statistical properties (discrete probability distributions of the mean wave parameters etc.) very close to the properties of the data obtained with SWAN, thus proving that this approach can be used as a reliable tool for wind wave simulation in coastal areas, complementary to (often computationally demanding) spectral wave models. [Copyright &y& Elsevier]

Summary: In the dune area of the Westhoek Nature Reserve, situated in the western Belgian coastal plain, two artificial tidal inlets were made aiming to enhance biodiversity. The infiltration of salt water in these tidal inlets was carefully monitored because a fresh water lens is present in the phreatic dune aquifer. This forms an important source of fresh water which is for instance exploited by a water company. The infiltration was monitored over a period of two years by means of electromagnetic borehole measurements (EM39) and by measurements of fresh water heads and temperature using a large number of observation wells. EM39 observations point to aquifer heterogeneity as a determining factor in the movement of the salt infiltration water. It is shown that part of the infiltration water moves further in the dunes instead of towards the sea. On the long term run, possibility exists that salt water enters the extraction’s capture zone. This issue needs further monitoring and study. Fresh water head and temperature data illustrate that the main period of infiltration is confined to spring tide when large amounts of salt water enter the tidal inlets. [Copyright &y& Elsevier]

Abstract: Anomalous morphological features within large estuaries may be: (1) recorders of external forces that periodically overwhelm the normal morphodynamic responses to estuarine energy fluxes, and (2) possible predictors of cycles of future coastal change. At the entrance to Willapa Bay, Washington, chronic beach erosion and frequent coastal flooding are related to the historical northward channel migration that destroyed the protective sand spits of Cape Shoalwater. Northward channel migration since the late 1800s conforms to the long-term net sediment transport direction. What requires explanation is periodic southward relocation of the trunk channel by as much as 5 km, and attendant construction of moderately large sand spits on the north side of the bay such as Kindred Island, Tokeland Peninsula, and Cape Shoalwater. Both autocyclic and allocyclic processes may have been responsible for trunk channel realignment and associated spit deposition. Channel recycling may occur when the main channel becomes overextended to the north and the tidal flow is inefficient because of its decreased gradient and increased susceptibility to shoaling by the growth and migration of tidal sand ridges. Under those conditions trunk channel relocation would be facilitated by increased wave heights and water levels of El Niño winter storms. However, co-seismic subsidence is the most likely mechanism for abruptly increasing sand supply and longshore transport that would favor discrete periods of channel relocation and spit deposition. Unless external forcing changes sand supply and predominant sediment transport directions in the future, the relative rise in sea level, frequent winter storms, and local deficit in the sand budget assure that beach erosion will continue at the mouth of this large estuary. [Copyright &y& Elsevier]

Abstract: Field observations of flow and sediment transport in a tributary channel through intertidal mudflats indicate that suspended sediment was closely linked to advection and dispersion of a tidal salinity front. During calm weather when tidal forcing was dominant, high concentrations of suspended sediment advected up the mudflat channel in the narrow region between salty water from San Francisco Bay and much fresher runoff from the small local watershed. Salinity and suspended sediment dispersed at similar rates through each tidal inundation, such that during receding ebbs the sediment pulse had spread spatially and maximum concentrations had decreased. Net sediment transport was moderately onshore during the calm weather, as asymmetries in stratification due to tidal straining of the salinity front enhanced deposition, particularly during weaker neap tidal forcing. Sediment transport by tidal forcing was periodically altered by winter storms. During storms, strong winds from the south generated wind waves and temporarily increased suspended sediment concentrations. Increased discharge down the tributary channels due to precipitation had more lasting impact on sediment transport, supplying both buoyancy and fine sediment to the system. Net sediment transport depended on the balance between calm weather tidal forcing and perturbations by episodic storms. Net transport in the tributary channel was generally offshore during storms and during calm weather spring tides, and onshore during calm weather neap tides. [Copyright &y& Elsevier]

Abstract: Bridge scour modeling requires storm surge hydrographs as open ocean boundary conditions for coastal waters surrounding tidal inlets. These open coast storm surge hydrographs are used to accurately determine both horizontal and vertical circulation patterns, and thus scour, within the inlet and bay for an extreme event. At present, very little information is available on the effect that tidal inlets have on these open coast storm surge hydrographs. Furthermore, current modeling practice enforces a single design hydrograph along the open coast boundary for bridge scour models. This study expands on these concepts and provides a more fundamental understanding on both of these modeling areas. A numerical parameter study is undertaken to elucidate the influence of tidal inlets on open coast storm surge hydrographs. Four different inlet–bay configurations are developed based on a statistical analysis of existing tidal inlets along the Florida coast. The length and depth of the inlet are held constant in each configuration, but the widths are modified to include the following four inlet profiles: 1) average Florida inlet width; 2) 100 m inlet width; 3) 500 m inlet width; and 4) 1000 m inlet width. Results from these domains are compared to a control case that does not include any inlet–bay system in the computational domain. The Advanced Circulation, Two-Dimensional Depth-Integrated (ADCIRC-2DDI) numerical code is used to obtain water surface elevations for all studies performed herein. The code is driven by astronomic tides at the open ocean boundary, and wind velocities and atmospheric pressure profiles over the surface of the computational domains. Model results clearly indicate that the four inlet–bay configurations do not have a significant impact on the open coast storm surge hydrographs. Furthermore, a spatial variance amongst the storm surge hydrographs is recognized for open coast boundary locations extending seaward from the mouth of the inlet. In addition, a storm surge study of Hurricane Ivan in the vicinity of Escambia Bay along the Panhandle of Florida is performed to assess the findings of the numerical parameter study in a real-life scenario. The main conclusions from the numerical parameter study are verified in the Hurricane Ivan study: 1) the Pensacola Pass–Escambia Bay system has a minimal effect on the open coast storm surge hydrographs; and 2) the open coast storm surge hydrographs exhibit spatial dependence along typical open coast boundary locations. The results and conclusions presented herein have implications toward future bridge scour modeling efforts. [Copyright &y& Elsevier]

Abstract: The paper presents an approach towards a medium-term (∼decades) modelling of water levels and currents in a shallow tidal sea by means of combined hydrodynamic and neural network models. The two-dimensional version of the hydrodynamic model Delft3D, forced with realistic water level and wind fields, is used to produce a two-year-database of water levels and currents in the study area. The linear principal component analysis (PCA) of the results is performed to reveal dominating spatial patterns in the analyzed dataset and to significantly reduce the dimensionality of the data. It is shown that only a few principal components (PCs) are necessary to reconstruct the data with high accuracy (over 95% of the original variance). Feed-forward neural networks are set up and trained to effectively simulate the leading PCs based on water level and wind speed and direction time series in a single, arbitrarily chosen point in the study area. Assuming that the spatial modes resulting from the PCA are ‘universally’ applicable to the data from time periods not modelled with Delft3D, the trained neural networks can be used to very effectively and reliably simulate temporal and spatial variability of water levels and currents in the study area. The approach is shown to be able to accurately reproduce statistical distribution of water levels and currents in various locations inside the study area and thus can be viewed as a reliable complementary tool e.g., for computationally expensive hydrodynamic modelling. Finally, a detailed analysis of the leading PCs is performed to estimate the role of tidal forcing and wind (including its seasonal and annual variability) in shaping the water level and current climate in the study area. [Copyright &y& Elsevier]

Abstract: In the paper two types of numerical models – a lumped-parameter model and a high-resolution two-dimensional hydrodynamic model – are used to analyse the response of a system of partially-connected tidal basins to inhomogeneous open sea forcing. The equations of the lumped-parameter model, suitable for an arbitrary number of basins with sloping walls, are formulated based on one-dimensional continuity and momentum equations. Numerical solutions to the equations are thoroughly examined, showing the influence of inhomogeneous open sea forcing and of geometrical parameters of the basins on the tidal range and the water transport through the system, with particular emphasis given to inter-basin water exchange and cumulative water transport through basins boundaries. The results of the lumped-parameter model simulations for the tidal basins of the German Wadden Sea are successfully compared with the results of calculations with the two-dimensional hydrodynamic model, which is used to investigate in more detail circulation patterns and the influence of specific local features of inlet bathymetry on the hydrodynamic processes in the study area. The influence of wind on the basins response is discussed as well. [Copyright &y& Elsevier]

Abstract: In this paper different strategies of morphological updating, as an important component of integrated modelling, are discussed, starting with the classical ‘tide-averaging’ approach in combination with the ‘continuity correction.’ An extension of the ‘continuity correction’ method, the so-called ‘RAM’ method, is then discussed. Next, the ‘online’ or ‘morphological factor’ approach is evaluated and compared with the previous approaches. Finally, a new, ‘parallel online’ method is presented which overcomes the problem of large intra-tidal variations in bathymetry when applying high morphological factors. The pros and cons of the different methods are compared and illustrated for a hypothetical case of a tidal inlet developing from an initially very schematised geometry. [Copyright &y& Elsevier]

Abstract: The Frisian Inlet is one of the tidal basins of the Dutch Wadden Sea. In 1969, its basin area was reduced by 30%. As documented by bathymetric surveys, this has led to an import of sediment of 30×106 m3 over the first 18 years. The study presented in this paper seeks to establish the mechanisms responsible for the passage of the sediment through the throat cross-section of the inlet channel. Emphasis is on a 14-day period of relative calm when sediment transport can be attributed solely to tidal currents. Use is made of continuous measurements of velocity, sand and silt concentration. The measurement station was located on one side of the throat cross-section in a water depth of approximately 6 m. For both the sand and silt fraction of the sediment, suspended load transport is the dominant transport mode. It is shown that for sand, concentration variations and net transport are determined by the local (in the throat section) velocity. Especially the residual velocity and tidal velocity asymmetry play an important role in the net sand flux. For silt, except for transport associated with locally generated vertical mixing, the net transport is largely determined by sedimentation–erosion processes in the basin and the silt concentration in the North Sea. Comparison with measurements in a station located in the middle of the throat section shows considerable difference in residual velocity and tidal velocity asymmetry. As a result, the sediment fluxes also differ. Accurately determining the net sediment flux in the throat section would require a dense net of measurement stations. [Copyright &y& Elsevier]

An axial convergence front system in Sand Shoal Inlet, VA, is analyzed. The fronts, which are parallel to the main channel and mostly within the channel, occur during different tidal stages within a 13-h observation period. A 25-ft boat is used to tow an acoustic Doppler current profiler to measure velocity profiles along an hour-glass shaped ship track. Salinity and temperature are measured using conductivity–temperature–depth sensors. A harmonic-statistic analysis is used to analyze the tide, tidal velocity, and mean velocity. The transverse convergence and divergence of velocity are calculated. The rms errors of the harmonic-statistic analysis of the elevation and velocity are about 0.28 m and 0.13 m/s (with a maximum velocity of over 2 m/s), respectively. On average, about 83%, 95%, and 70% of the variabilities of the elevation, longitudinal and transverse velocities, respectively, can be explained by the M2 tidal and subtidal constituents. Strong transverse velocity convergences are identified by the analysis and are generally consistent with the observed front positions. The analysis shows that the front system is apparently generated by a combination of several mechanisms including (1) differential rotation of the tidal ellipses and spatial variations of the major axes of the tidal ellipses, owing to the strong bottom friction, and (2) a strong geometric convergence at the inlet. Density effect is found to be negligible and the planetary vorticity tilt effect is also unimportant because of a much higher relative vorticity. The observed front system is distinguished from the conventional estuarine axial convergence fronts which require a strong along channel density gradient. Therefore, in estuaries and coastal embayment where both tides and density gradients are important and where cross-channel bathymetry change is present, the frontal genesis can be a combination of several processes including the tidal convergence discussed here. [Copyright &y& Elsevier]

The Haringvliet estuary is part of the Dutch Delta coast. Since 1950, several large coastal engineering projects have been carried out in the Haringvliet area. The most important of these is the closure of the estuary by the construction of a dam with sluices (finished in 1970). Land reclamation projects of the Maasvlakte (1964–1976) and the so-called Slufter (1986–1987) have also been carried out. These projects have profoundly affected the hydrodynamics and therefore the morphology of the area. New interventions are under discussion and to be able to predict their impact on the morphology, it is necessary to understand the morphological developments caused by the past interventions. In this study, the development with time of the sand volume in the Haringvliet estuary after closure has been studied using bathymetric measurements of the years 1970, 1972, 1979, 1980, 1986 and 1990 until 1999. The changes in sand volume above NAP (Dutch Ordnance Level) −10 m relative to 1970 have been determined. The area in which these volumes have been calculated had to be chosen very carefully to diminish the effects of all other human interventions. As was expected, the estuary shows sedimentation. It could be concluded that the adaptation time scale is about 11 years and that the equilibrium volume has almost been reached in the year 2000. [Copyright &y& Elsevier]

Despite their global abundance and high ecological and socio-economic significance, the dynamics of coastal inlets often remain poorly quantified at multi-decadal time scales. Here, we introduce InletTracker (https://github.com/VHeimhuber/InletTracker), a new tool that reconstructs the time-evolving state of dynamic coastal inlets over the last 30+ years from publicly available Landsat 5, 7 and 8 and Sentinel-2 satellite imagery. InletTracker is a Google Earth Engine enabled python toolkit that uses a novel least-cost pathfinding approach to trace inlets along and across the berm (i.e., barrier, bar), and then analyses the resulting transects to infer whether an inlet is open or closed. To evaluate the performance of InletTracker, we applied the tool at 12 intermittent coastal inlets with different maximum inlet widths (≤30-200 m), geomorphological setting and opening frequency located across Southeastern and Southwestern Australia. This exercise involved 6363 unique binary inlet state predictions (i.e., open vs. closed) that were validated against visually inferred inlet states (from the satellite imagery itself), on-ground observational records, and in-situ water levels from inside the inlets. InletTracker reproduced the visually inferred inlet states with an average accuracy across all sites of 89% for the combined Landsat and Sentinel-2 record (15-30 m resolution) and 94% for the Sentinel-2 record only (10 m resolution). Overall, we found good agreement between the predictions of the tool and the three independent validation datasets for all but the smallest sites. Our results demonstrate that InletTracker will enable coastal engineers, managers, and researchers to gain new insights into the dynamics and drivers of coastal inlets or similar shallow water landforms such as river mouths, tidal flats, floodplains, wetlands or delta channel networks. Further, the high spatial (i.e., 10 m) and temporal (i.e., 5-daily) resolution provided by Sentinel-2 makes InletTracker a viable option for near real-time monitoring of even relatively small inlets with a minimum channel width of around 10 m and frequent, short-duration, openings. [Display omitted] • We present a new method for automated monitoring of dynamic coastal inlets. • Path finding is used to accurately trace openings through multi-decadal imagery. • The method is tested based on 12 intermittent coastal inlets in Australia. • Validation revealed excellent performance for detecting inlet states. • The tool will provide new insights into inlet dynamics around the globe. [ABSTRACT FROM AUTHOR]

Tidal inlets are crucial landforms that control the exchange of water and sediment between the open sea and back-barrier basins. Despite the well-established relationship between tidal prism and inlet cross section area, some aspects of tidal inlet geometry remain unconstrained. What processes set their width to depth ratio (or aspect ratio)? What controls the presence of a single-thread versus a compound channel within the same inlet? Do these relationships change with engineering activities? These questions were investigated by compiling and analyzing a database with 226 inlets worldwide. We found that the aspect ratio has a weak dependency on tidal range and wave height. The aspect ratio varies by at least an order of magnitude, and this variability is likely associated with the variability in the widening process, e.g., the bank erodibility. Engineered inlets tend to have smaller widths and aspect ratios than natural inlets. Within natural inlets, multiple channels tend to form when the inlet width exceeds approximately 1 km. We developed an idealized barrier-inlet system using the detailed 2D hydro-morphodynamic model Delft3D to investigate the long-term morphological evolution of inlets. Two parameters greatly affect the aspect ratio: the transverse bed gradient factor for sediment transport (α bn) and the dry cell erosion factor (θ sd) , which allows for erosion of dry cells adjacent to a wet cell. Removing the dry cell erosion effectively "armors" the side of the inlets and thus produces inlets with a small aspect ratio, which resembles the geometry of engineered inlets. From model sensitivity analysis, we found that α bn = 5–10 and θ sd = 0.3–1.0 provides inlet configurations that best agree with observations. Despite the dry cell erosion and the transverse transport parameters being a simplified representation of bank erosion processes, their calibration allows to reproduce realistic inlet aspect ratio. • Existing knowledge of tidal inlet geometry was expanded using a comprehensive dataset and morphodynamic model. • We compared natural and engineered inlets, highlighting their differences in aspect ratios and channel configurations. • Appropriate values for 2 key model parameters (dry cell erosion factor and transverse bed gradient factor) were identified. [ABSTRACT FROM AUTHOR]

• The Bruun method was adapted for assessing tidal inlet short term morphodynamics. • Instantaneous tidal prism/marine drift ratio is used for tidal inlet assessment. • Shoaling occurs when the tidal prism/marine drift ratio decreases under 20. • Annual total longshore transport rate at Praia Seca (RJ - Brazil) is calculated. • Morphodynamics of an alternative inlet channel in the Araruama Lagoon is studied. Longshore sediment transport and tidal prism are key factors in analyzing the stability and morphodynamics of a tidal inlet. Stablished by the Bruun theory, the ratio between the maximum spring tidal prism (P) and the annual total littoral drift (M T) is a parameter widely used to diagnose the stability condition of tidal inlets and to validate inlet morphological modeling results. However, the P / M T relationship is adequate for mid-term and long-term analysis only (i.e. weeks, months, years or decades). Depending on the wave climate, one may observe intense accretion in a tidal inlet in a time scale of hours to few days during storm events. No empirical criterion is yet known to be applicable for supporting analysis in such a short time scale. This work presents a modified approach of the traditional Bruun criterion, adapted for assessing short-term (i.e. hours or days) morphological evolution of tidal inlets. Instead of P and M T , the method here addressed considers the ratio between the tidal prism (P i) and the longshore transport volume (M T i ) integrated both over the flood period of every tidal cycle. This methodology was applied in the analysis of storm and post-storm induced morphodynamic response of a projected tidal channel, proposed to improve water quality in the Araruama Lagoon, Rio de Janeiro, Brazil. Hydro-sedimentological numerical modeling was used to simulate a scenario which encompassed three cycles of storm induced accretion and post-storm induced inlet development. Correlation was noticed between the patterns of short-term morphodynamic response and the temporal variations of the instantaneous P i / M T i ratio. This research also presents calculations on the longshore sediment transport rate during the four seasons for the studied region. [ABSTRACT FROM AUTHOR]