Inlet dynamics

The village of Lahou Kpanda (Grand Lahou, Côte d'Ivoire), located to the immediate west of the mouth of the Bandama River, on the barrier island of the Tagba lagoon, is highly vulnerable to coastal erosion. It is directly threatened by the migration of the river mouth, which has been occurring at an average speed of 160 m/year over the last 10 years, as well as by the risks of flooding and coastal flooding which the effects of climate change will exacerbate further. This article presents the study, beginning in 2019 and financed by the WACA programme, which contributed to the choice and dimensioning of a sustainable solution for stabilization of the Grand-Lahou sandy barrier island.

With the investments in the defense industry and technological advancements today, supersonic flights and the related design and analysis studies are becoming increasingly important. One of the main challenges encountered in the design of aircraft flying at supersonic speeds is the aerodynamic effect known as "spillage drag." This undesired effect arises when the air intake provides more air than required by the engine, negatively impacting aerodynamic efficiency. The additional drag force it creates leads to a decrease in engine performance. In the relevant literature, it has been observed that optimization studies aimed specifically at reducing spillage drag for air intakes have not been conducted under supersonic conditions. Air intakes play a critical role in supplying air to aircraft engines. During transonic and supersonic flights, they slow down the air properly and direct it to the engine to ensure efficient operation. However, in this process, spillage drag can become a significant issue when the required mass flow rate for the engine falls below the necessary level. The spilled air increases drag forces, thus reducing the efficiency of engine performance. In this study, it is aimed to examine the effects of spillage drag in air intakes under supersonic conditions using computational methods and to observe the changes in this effect through the optimization of the reference air intake. In the study, the NACA 1-89-100 was used as the reference air intake geometry, and its aerodynamic optimization was performed. The necessary data for the NACA 1-89-100 air intake geometry were obtained from NASA's published reports. In calculating the increase/decrease in spillage drag, the capture area ratios were analyzed. The validation method used in the study was based on the work of Denner and colleagues in 1998 and was validated with NASA's experimental data. During the optimization process, a contraction was applied to the front section of the air intake to change the capture area ratio, and how this optimization affected the spillage drag was examined. The results obtained were evaluated in terms of the advantages and disadvantages of minimizing spillage drag. With this study, it is aimed to guide future research on the performance optimization of air intakes and the minimization of drag forces.

The village of Lahou Kpanda (Grand Lahou, Côte d'Ivoire), located to the immediate west of the mouth of the Bandama River, on the barrier island of the Tagba lagoon, is highly vulnerable to coastal erosion. It is directly threatened by the migration of the river mouth, which has been occurring at an average speed of 160 m/year over the last 10 years, as well as by the risks of flooding and coastal flooding which the effects of climate change will exacerbate further. This article presents the study, beginning in 2019 and financed by the WACA programme, which contributed to the choice and dimensioning of a sustainable solution for stabilization of the Grand-Lahou sandy barrier island.

The village of Lahou Kpanda (Grand Lahou, Côte d'Ivoire), located to the immediate west of the mouth of the Bandama River, on the barrier island of the Tagba lagoon, is highly vulnerable to coastal erosion. It is directly threatened by the migration of the river mouth, which has been occurring at an average speed of 160 m/year over the last 10 years, as well as by the risks of flooding and coastal flooding which the effects of climate change will exacerbate further. This article presents the study, beginning in 2019 and financed by the WACA programme, which contributed to the choice and dimensioning of a sustainable solution for stabilization of the Grand-Lahou sandy barrier island.

The rocky and indented coast of NW Iberia is characterized by the presence of highly valuable and vulnerable, small and shallow barrier–lagoon systems structurally controlled. The case study was selected to analyse barrier–lagoon evolution based on detailed sedimentary architecture, chronology, geochemical and biological proxies. The main objective is to test the hypothesis of structural control and the significance at regional scale of any high-energy event recorded. This work is also aimed at identifying general patterns and conceptualizing the formation and evolution of this type of coastal systems. The results allowed us to establish a conceptual model of Holocene evolution that applies to rock-bounded barrier–lagoon systems. The initial stage (early Holocene) is characterized by freshwater peat sedimentation and ended by marine flooding. The timing of the marine flooding depends on the relation between the elevation of the basin and the relative mean sea-level position; the low...

The village of Lahou Kpanda (Grand Lahou, Côte d'Ivoire), located to the immediate west of the mouth of the Bandama River, on the barrier island of the Tagba lagoon, is highly vulnerable to coastal erosion. It is directly threatened by the migration of the river mouth, which has been occurring at an average speed of 160 m/year over the last 10 years, as well as by the risks of flooding and coastal flooding which the effects of climate change will exacerbate further. This article presents the study, beginning in 2019 and financed by the WACA programme, which contributed to the choice and dimensioning of a sustainable solution for stabilization of the Grand-Lahou sandy barrier island.

The Integrated Ocean Observing System Super-regional Coastal Modeling Testbed had one objective to evaluate the capabilities of three unstructured-grid fully current-wave coupled ocean models (ADCIRC/SWAN, FVCOM/SWAVE, SELFE/WWM) to simulate extratropical storm-induced inundation in the US northeast coastal region. Scituate Harbor (MA) was chosen as the extratropical storm testbed site, and model simulations were made for the 24-27 May 2005 and 17-20 April 2007 (''Patriot's Day Storm'') nor'easters. For the same unstructured mesh, meteorological forcing, and initial/boundary conditions, intermodel comparisons were made for tidal elevation, surface waves, sea surface elevation, coastal inundation, currents, and volume transport. All three models showed similar accuracy in tidal simulation and consistency in dynamic responses to storm winds in experiments conducted without and with wave-current interaction. The three models also showed that wave-current interaction could (1) change the current direction from the along-shelf direction to the onshore direction over the northern shelf, enlarging the onshore water transport and (2) intensify an anticyclonic eddy in the harbor entrance and a cyclonic eddy in the harbor interior, which could increase the water transport toward the northern peninsula and the southern end and thus enhance flooding in those areas. The testbed intermodel comparisons suggest that major differences in the performance of the three models were caused primarily by (1) the inclusion of wave-current interaction, due to the different discrete algorithms used to solve the three wave models and compute water-current interaction, (2) the criterions used for the wet-dry point treatment of the flooding/drying process simulation, and (3) bottom friction parameterizations.

The Integrated Ocean Observing System Super-regional Coastal Modeling Testbed had one objective to evaluate the capabilities of three unstructured-grid fully current-wave coupled ocean models (ADCIRC/SWAN, FVCOM/SWAVE, SELFE/WWM) to simulate extratropical storm-induced inundation in the US northeast coastal region. Scituate Harbor (MA) was chosen as the extratropical storm testbed site, and model simulations were made for the 24-27 May 2005 and 17-20 April 2007 (''Patriot's Day Storm'') nor'easters. For the same unstructured mesh, meteorological forcing, and initial/boundary conditions, intermodel comparisons were made for tidal elevation, surface waves, sea surface elevation, coastal inundation, currents, and volume transport. All three models showed similar accuracy in tidal simulation and consistency in dynamic responses to storm winds in experiments conducted without and with wave-current interaction. The three models also showed that wave-current interaction could (1) change the current direction from the along-shelf direction to the onshore direction over the northern shelf, enlarging the onshore water transport and (2) intensify an anticyclonic eddy in the harbor entrance and a cyclonic eddy in the harbor interior, which could increase the water transport toward the northern peninsula and the southern end and thus enhance flooding in those areas. The testbed intermodel comparisons suggest that major differences in the performance of the three models were caused primarily by (1) the inclusion of wave-current interaction, due to the different discrete algorithms used to solve the three wave models and compute water-current interaction, (2) the criterions used for the wet-dry point treatment of the flooding/drying process simulation, and (3) bottom friction parameterizations.

The Keweenaw Waterway is a navigation passage with openings to Lake Superior at either end. Analysis of wind data and moored thermistor measurements indicates that movement of water into and out of the waterway is strongly influenced by surface winds through at least two mechanisms. One is direct forcing of waterway flows by the surface wind stress. The other is flow driven by pressure gradients arising from wind-driven changes in coastal lake level. Not surprisingly, the relative importance of direct wind forcing in driving near-entry flows appears to diminish with increasing depth. Also indicated is a tendency for winds to generate counterbalancing flows at the two entries, with wind-driven inflow at one entry matched by wind-driven outflow at the other entry. On a number of occasions, temperature data indicate flow out of the waterway entering a coastal water column modified by upwelling. This is presumably because upwelling favorable winds tend to depress coastal lake level, and create a pressure gradient driving flow out of the waterway.

INTRODUCTION Dikes protect large parts of the Netherlands against storm surges and wave attack. As described in Van Dongeren et al. (2007), these primary coastal defenses must be checked every five years by the best available methods to verify whether they comply with the required level of protection on the basis of Hydraulic Boundary Conditions (HBC). For a location along a primary coastal defense the HBC consist of a combination of normative wave conditions and water levels. Presently, a number of model studies are carried out in the framework of the SBW (Sterkte en Belasting Waterkeringen: Strength and Loads on Water Defenses) with the overall aim to improve the quality of the models and methods used to derive these HBC in the Wadden Sea. This is a shallow sea in the north of the Netherlands and protected from the North Sea by a number of barrier islands (Figure 1). Tidal flows enter and leave the Wadden Sea via a number of tidal inlets. North Sea waves may also penetrate through...

The rocky and indented coast of NW Iberia is characterized by the presence of highly valuable and vulnerable, small and shallow barrier–lagoon systems structurally controlled. The case study was selected to analyse barrier–lagoon evolution based on detailed sedimentary architecture, chronology, geochemical and biological proxies. The main objective is to test the hypothesis of structural control and the significance at regional scale of any high-energy event recorded. This work is also aimed at identifying general patterns and conceptualizing the formation and evolution of this type of coastal systems. The results allowed us to establish a conceptual model of Holocene evolution that applies to rock-bounded barrier–lagoon systems. The initial stage (early Holocene) is characterized by freshwater peat sedimentation and ended by marine flooding. The timing of the marine flooding depends on the relation between the elevation of the basin and the relative mean sea-level position; the low...

Nador lagoon is a coastal system connected to the sea through a narrow and shallow inlet; understanding its hydraulic performance is required for its design and operation. This paper investigates the hydrodynamic impacts of the whole lagoon due to tidal waves using a numerical approach. In this study we use a two-dimensional, depth-averaged hydrodynamic model based on so-called shallow water equations solved within triangular mesh by a developed efficient finite volume method. The method was calibrated and validated against observed data and applied to analyze and predict water levels, tidal currents, and wind effects within the lagoon. Two typical idealized scenarios were investigated: tide only and tide with wind forcing. The predicted sea surface elevations and current speeds have been presented during a typical tidal period and show correct physics in different scenarios.

The present paper tackles morphological modeling of a rare case of a re-migrating inlet to be used as the basis of a fishery port site selection study. The Tang inlet, located on the south-eastern shores of Iran, has so far been experiencing a cyclic migration with a return period of approximately a decade. In order to grasp the essence of the morphological behavior of the inlet, a two-fold site monitoring campaign was performed, consisting of a shoreline evolution study using aerial & satellite imagery for the outside of the bay as well as a sedimentation pattern comparison based on past hydrographical survey results for the inside of the bay utilizing ArcGIS software. Subsequently, numerical modeling of the inlet comprising of nearshore wave transformation, tidal regime of the bay, one-line coastline evolution and two-dimensional sediment transport within the bay was carried out utilizing MIKE 21 package. Ebb channel switching from a westerly to an easterly orientation is deemed t...

Understanding water dynamics and the processes affecting water elevation in the lagoon is important in understanding how barrier-lagoon systems work and, in particular, how it affects sediment distribution and architecture. It is also important in resolving a number of environmental problems related to flooding and land management. Louro barrier-lagoon system, on the Atlantic coast (Ría de Muros, Spain), has been studied to observe water-stage fluctuations and boundary conditions for inflow and outflow, from November 2009 to June 2010. Louro barrier-lagoon is disconnected from the open sea most of the year and over the last 10 years it rarely opened. Nevertheless during the monitored interval from November 2009 to June 2010 it opened at least 5 times due to a particularly stormy year. Results show that when the berm is well-developed and the inlet is not open, marine waters enter the inner lagoon by over-passing the beach berm by over-spilling during high spring tides. Flooding wate...

This study aimed to investigate the sedimentation mechanism at Pars port complex inlet (petrochemical and services ports in Iran) under the effects of wind-waves and tidal currents and to provide solutions to reduce sedimentation by changing the port plan. For this purpose, at first, the modeling of changes in water level and tidal currents in the area was conducted. The results for the currents and waves were evaluated and validated using the measured field data. The one-dimensional sediment transport potential was calculated by about 33,000 cubic meters per year. The analysis of two-dimensional sediment transport phenomena within the ports and inlets showed that tidal currents patterns that are parallel to the coast and the waves in the region are the most important factors in sedimentation. Accordingly, to minimize sedimentation and to investigate the effect of the geometric shape of the port, three configurations were proposed for ports, and the patterns of sedimentation were evaluated in the new arrangements.

In the shallow water region, when the waves start to interact with the ground, resonant energy transfer within the sea state enhances till the point when the wave spectrum changes its form within some wavelengths. After this point other nonlinear processes like wave breaking, bragg-scattering, bottom-friction and near-resonant wave-wave interactions govern the evolution of the wave spectrum. Most of the coastal structures, which are matter to coastal erosion, are located in shallow water where these processes become important. One class of wave models, the so called "spectral wave models", have the ability to hindcast the wave climate in deep and shallow water and have certain advantages in comparison with phase resolving models. In the last years these models are coupled with morphodynamic models like TIMOR (Tidal Morphodynamics) or SHYFEM (Shallow Water Hydrodynamic Finite Element Model, Umgiesser et al. (2004)) in order to investigate the morphodynamic evolution in the near shore. The WWM (Wind Wave Model; Hsu et al. (2004)) is one of these spectral wave models that have a physical formulation similar to the well known SWAN model but with the benefit that it works on unstructured meshes. In this study we will show the verification results for an alternative numerical scheme for the solution of the Wave Action Equation (WAE) in spatial space on a triangular mesh and first results of the model coupling between the SHYFEM model and the WWM for the case of the Lagoon of Venice.

The present paper tackles morphological modeling of a rare case of a re-migrating inlet to be used as the basis of a fishery port site selection study. The Tang inlet, located on the south-eastern shores of Iran, has so far been experiencing a cyclic migration with a return period of approximately a decade. In order to grasp the essence of the morphological behavior of the inlet, a two-fold site monitoring campaign was performed, consisting of a shoreline evolution study using aerial & satellite imagery for the outside of the bay as well as a sedimentation pattern comparison based on past hydrographical survey results for the inside of the bay utilizing ArcGIS software. Subsequently, numerical modeling of the inlet comprising of nearshore wave transformation, tidal regime of the bay, one-line coastline evolution and two-dimensional sediment transport within the bay was carried out utilizing MIKE 21 package. Ebb channel switching from a westerly to an easterly orientation is deemed t...

In 2011 new Hydraulic Boundary Conditions must be established for the statutory assessment of flood protection in the Wadden Sea area, which is a complex tidal system in the northern part of the Netherlands. The aim is to base these normative wave conditions on the wave simulation model SWAN and the probabilistic method Hydra-K, to be consistent with other systems as the Holland Coast and the Zeeland Delta. Assumptions made for the latter water systems, like steady state wind forcing, uniform water levels and neglect of currents, are not valid in the tidal basin of the Wadden Sea. A schematic temporal variation of both wind direction and wind speed is applied to define wind fields that drive the hydrodynamic computations. Both wind fields and resulting water level and current fields form the input of SWAN computations for a large number of combinations of basic wind speed and wind direction, offshore surge level and phase difference between tide and maximum wind speed. The result is...

The wave characteristics and wave-current interaction in the six tidal inlets connecting the Barataria Basin and the northern Gulf of Mexico are investigated during spring-summer time period when both cold front passage and persistent southeast wind events exist. A fully-coupled unstructured-grid, three-dimensional, FVCOM-SWAVE model is employed and validated against observational data during April-June 2010. Model simulation results indicate that waves in the shelf side of the inlets are mainly wind seas and swells from the Gulf of Mexico that are modified by ocean currents in the Louisiana Bight. These currents include Mississippi River plume, buoyancy-and wind-driven alongshore current, as well as the tidal jet in the Barataria Pass. The bay side of the inlets, similar to the interior of the Barataria Basin, is dominated by locally generated waves. In the middle of the inlets, both wind seas and swells are presented at times, though different inlets behave differently in terms of contribution from each component. The contribution of local wind seas enhances during cold front passage. Contrastingly, the influence of swells from continental shelf is more pronounced during persistent southeast wind event. FVCOM-SWAVE predicts a decrease in significant wave height inside the Louisiana Bight due to current-induced refraction and wave stretching effect caused by clockwise gyre from Mississippi plume. The modulation of significant wave height at Barataria Pass due to partial wave blocking for the opposing current, and wave stretching for the following current can be up to 20%. The effect of depth-induced breaking and bottom friction overshadows the one from wave-current interaction at other shallower inlets.

The present paper tackles morphological modeling of a rare case of a re-migrating inlet to be used as the basis of a fishery port site selection study. The Tang inlet, located on the south-eastern shores of Iran, has so far been experiencing a cyclic migration with a return period of approximately a decade. In order to grasp the essence of the morphological behavior of the inlet, a two-fold site monitoring campaign was performed, consisting of a shoreline evolution study using aerial & satellite imagery for the outside of the bay as well as a sedimentation pattern comparison based on past hydrographical survey results for the inside of the bay utilizing ArcGIS software. Subsequently, numerical modeling of the inlet comprising of nearshore wave transformation, tidal regime of the bay, one-line coastline evolution and two-dimensional sediment transport within the bay was carried out utilizing MIKE 21 package. Ebb channel switching from a westerly to an easterly orientation is deemed to occur due to self-suffocation as a result of the presence of an existing offshore rock formation, as well as the salient making potential of the rock system. On the other hand, the closure of the east-facing channel is mainly attributed to diffraction currents due to Monsoon southerly waves helped by sedimentation load from inside the bay system due to floods & ebb currents.

Understanding water dynamics and the processes affecting water elevation in the lagoon is important in understanding how barrier-lagoon systems work and, in particular, how it affects sediment distribution and architecture. It is also important in resolving a number of environmental problems related to flooding and land management. Louro barrier-lagoon system, on the Atlantic coast (Ría de Muros, Spain), has been studied to observe water-stage fluctuations and boundary conditions for inflow and outflow, from November 2009 to June 2010. Louro barrier-lagoon is isconnected from the open sea most of the year and over the last 10 years it rarely opened. Nevertheless during the monitored interval from November 2009 to June 2010 it opened at least 5 times due to a particularly stormy year. Results show that when the berm is well-developed and the inlet is not open, marine waters enter the inner lagoon by over-passing the beach berm by over-spilling during high spring tides. Flooding waters enter the lagoon through a partial channel which shows a strong slope from the berm inwards, reaching a supercritical flow and introducing marine waters, far into the eastern part of the lagoon. The sand is
transported inwards forming lobe-shaped bars into the lagoon and depositing a tidal flood-delta. However, to develop a fully open inlet, which involves the excavation of a channel, water over-elevation has to occur in the lagoon to build enough water pressure and potential energy to cut the berm and to connect the lagoon with the sea.