Coastal hydrodynamics and wave mechanisms along the West coast of the Mekong Delta

Abstract. This work compares meteorological results from different regional climate model (RCM) implementations in the Mediterranean area, with a focus on the northern Adriatic Sea. The need to use these datasets as atmospheric forcings (wind and atmospheric pressure fields) for coastal hydrodynamic models to assess future changes in the coastal hydrodynamics, is the basis of the presented analysis. It would allow the assessment of uncertainties due to atmospheric forcings in providing coastal current, surge and wave climate changes from future implementations of hydrodynamic models. Two regional climate models, with different spatial resolutions, downscaled from two different global climate models (whose atmospheric components are, respectively, ECHAM4 and ECHAM5), were considered. In particular, the RCM delivered wind and atmospheric pressure fields were compared with measurements at four stations along the Italian Adriatic coast. The analyses were conducted using a past control period, 1960–1990, and the A1B IPCC future scenario (2070–2100). The chosen scenario corresponds to a world of very rapid economic and demographic growth that peaks in mid-century, with a rapid introduction of new efficient technologies, which balance fossil and non-fossil resources (IPCC, 2007). Consideration is given to the accuracy of each model at reproducing the basic statistics and the trends. The role of models' spatial resolution in reproducing global and local scale meteorological processes is also discussed. The Adriatic Sea climate is affected by the orography that produces a strengthening of north-eastern katabatic winds like bora. Therefore, spatial model resolution, both for orography and for a better resolution of coastline (Cavaleri et al., 2010), is one of the important factors in providing more realistic wind forcings for future hydrodynamic models implementations. However, also the characteristics in RCM setup and parameterization can explain differences between the datasets. The analysis from an ensemble of model implementation would provide more robust indications on climatic wind and atmospheric pressure variations. The scenario-control comparison shows a general increase in the mean atmospheric pressure values while a decrease in mean wind speed and in extreme wind events is seen, particularly for the datasets with higher spatial resolution.

Modelling the manoeuvring behaviour of an ULCS in coastal waves

This chapter presents an overview of the available methods for modeling coastal waves. First, an overview of the relevant coastal processes, from shoaling to turbulent mixing, is provided to establish a basis to compare the various modeling approaches. The bulk of the discussion centers on modeling wind waves and includes a brief overview of the linear and analytical theory available to quantify coastal transformation, and then follows with a summary of spectral and phase-resolving approaches. Modeling long waves is discussed next, with a focus on tsunami simulation. Finally, the chapter summarizes techniques to couple the various models and reviews recent advances in the topic.

Phase plane bifurcation analysis of water wave dynamics in the simplified modified Camassa–Holm model with friction and wind effects

The understanding of the morphodynamics of harmonic bed forms on the seabed is essential for modeling marine sediment transport and coastal morphologic development. Previous research has mainly focused on the type and distribution of bed forms, but areally extensive data and time series of seabed features are scarce. Multibeam and side‐scan sonar data from four expeditions reveal the contrasts between a coastal site with asymmetric and flattened, three‐dimensional (3‐D) compound sand waves on a shoreface‐connected ridge and an offshore site with asymmetric and sharp‐crested, 2‐D compound sand waves. Migration rates of the coastal sand waves are 6.5–20 m yr−1, while migration rates of the offshore sand waves are −3.6 to 10 m yr−1. This contrasting morphology and dynamic behavior of compound sand waves at the two North Sea sites is explained by differences in the relative importance of tidal currents and wave activity near the bed. These new field data provide parameters and boundary conditions for sand transport models, while the empirically derived behavior of sand waves may be used to validate sand transport and sand wave models.

Properties of internal wave fronts or Kelvin fronts travelling eastward in the equatorial waveguide are studied, motivated by recent studies on coastal Kelvin waves and jumps and new data on equatorial Kelvin waves. It has been recognized for some time that nonlinear equatorial Kelvin waves can steepen and break, forming a broken wave of depression, or front, propagating eastward. The three-dimensional structure of the wave field associated with such a front is considered. As for linear Kelvin waves, the front is symmetrical with respect to the equator. Sufficiently far away from the front, the wave profile is Gaussian in the meridional direction, with the equatorial Rossby radius of deformation being its decay scale. Due to nonlinearity, the phase speed of the front is greater than that of linear Kelvin waves, resulting in a supercritical flow. This leads to the resonant generation of equatorially trapped gravity–inertial (or Poincaré) waves, analogous in principle to the resonant mechanism for nonlinear coastal Kelvin waves. First-mode symmetrical Poincaré waves are generated, with their wavelength determined by the amplitude of the front. Finally, the propagation of a Kelvin front gives rise to a nonzero poleward mass transport above the thermocline, in consequence of which there is a poleward heat flux.

A baroclinic shallow-water model is developed to investigate the effect of the orientation of the eastern ocean boundary on the behavior of equatorial Kelvin waves. The model is formulated in a spherical polar coordinate system and includes dissipation and non-linear terms, effects which have not been previously included in analytical approaches to the problem. Both equatorial and middle latitude response are considered given the large latitudinal extent used in the model. Baroclinic equatorial Kelvin waves of intraseasonal, seasonal and annual periods are introduced into the domain as pulses of finite width. Their subsequent reflection, transmission and dissipation are investigated. It is found that dissipation is very important for the transmission of wave energy along the boundary and for reflections from the boundary. The dissipation was found to be dependent not only on the presence of the coastal Kelvin waves in the domain, but also on the period of these coastal waves. In particular the dissipation increases with wave period. It is also shown that the equatorial β-plane approximation can allow an anomalous generation of Rossby waves at higher latitudes. Nonlinearities generally have a small effect on the solutions, within the confines of this model.Key words. Oceanography: general (equatorial oceanography; numerical modeling) · Oceanography: physical (eastern boundary currents)

Wave propagation in disordered (random) media is the underlying theme. We study the effective behavior of long coastal waves that travel over rough topographies. The topographies analyzed contain a smooth slowly varying profile together with disordered small-scale features. The mathematical model is a conservation law with random coefficients. The main asymptotic (stochastic theory) result is that the medium fluctuations cause the propagating pulse to broaden as it travels. The so called apparent diffusion (or pulse shaping) depends only on the traveling distance and the statistics of the random medium fluctuations. Thus, the broadening can be described in a deterministic way independently of the particular medium realization. This is confirmed numerically. Numerical experiments also show that the theory describing pulse shaping is very robust. Nonlinear shallow water simulations show that small amplitude pulse shaping is not affected by higher order terms. The robustness of the theory is observed numerically for a wide parameter regime. We vary both the microscale fluctuation level as well as the horizontal length scales of the topography. The numerical experiments produce very good results regarding the prediction for the wavefront attenuation.

In the last two decades, myriad numerical models and modeling techniques have been developed for simulating the properties and behavior of ocean waves under a variety of conditions. These include models for coastal wave propagation, wave agitation in harbors, overtopping of seawalls, wave-structure interaction, etc. Thanks to recent advances that have occurred in the past 20 years in computing power, both large-scale ocean and refined localscale coastal wave modeling can now be performed. The modeling techniques are based on a variety of governing equations, including Laplace equation, Boussinesq equations, Navier-Stokes equations, energy-balance equations, etc., involving either the steady or the unsteady mode, and either one, two, or three dimensions as well as numerous approximations. The numerical techniques also display wide variation: finite differences, finite elements, boundary elements, volume of fluid, meshless computations, etc. This explosion of modeling methods is certainly admirable and attests to the dynamism of the field; however, it sometimes confronts practitioners engineers needing models for project applications, researchers, model developers, and managers with confusion, because the pros and cons of certain models vis-a-vis others are infrequently discussed. This issue has occasionally been addressed in brief review papers Panchang et al. 1999; Isobe 1999, but Professor Pengzhi Lin’s recent book Numerical Modeling of Water Waves is, simply stated, a superb contribution. It is comprehensive and authoritative, covering practically the entire spectrum of modeling applications and methodologies that one encounters in this field. It is a

Abstract. A baroclinic shallow-water model is developed to investigate the effect of the orientation of the eastern ocean boundary on the behavior of equatorial Kelvin waves. The model is formulated in a spherical polar coordinate system and includes dissipation and non-linear terms, effects which have not been previously included in analytical approaches to the problem. Both equatorial and middle latitude response are considered given the large latitudinal extent used in the model. Baroclinic equatorial Kelvin waves of intraseasonal, seasonal and annual periods are introduced into the domain as pulses of finite width. Their subsequent reflection, transmission and dissipation are investigated. It is found that dissipation is very important for the transmission of wave energy along the boundary and for reflections from the boundary. The dissipation was found to be dependent not only on the presence of the coastal Kelvin waves in the domain, but also on the period of these coastal waves. In particular the dissipation increases with wave period. It is also shown that the equatorial β-plane approximation can allow an anomalous generation of Rossby waves at higher latitudes. Nonlinearities generally have a small effect on the solutions, within the confines of this model.Key words. Oceanography: general (equatorial oceanography; numerical modeling) · Oceanography: physical (eastern boundary currents)

Hydrodynamic modelling is commonly conducted with various numerical tools to analyse intricate coastal processes. These platforms facilitate efficient setups and enable detailed visualisations of current flows, wave behaviour, and the potential for overtopping. Although they demand significant input data and processing time, numerical modelling plays a crucial role, especially in data-deficient and physically demanding areas such as regions with numerous islands. This paper outlines a comprehensive numerical modelling approach utilizing the MIKE-21 Hydrodynamic module, which is tailored for coastal simulations in the archipelagic areas of Southeast Asia. The focus of the study is Johor, Malaysia, situated at the southern end of the region, where intricate shoreline dynamics and island arrangements affect current patterns and wave effects. Hydrodynamic simulations were conducted to examine current direction, velocity, and the potential for wave overtopping at eight selected coastal sites, utilising wind and wave data collected in 2024. The methodology is highlighted, covering aspects such as mesh creation, wind integration, bathymetric setup, and calibration of simulations. This paper offers a replicable modelling process for researchers and planners working in similarly intricate maritime settings. The findings reveal that the eastern coastline of Johor experiences greater wave energy and current flows than the western side, indicating a higher susceptibility to erosion and structural strain.

Environmental geophysics holds significant but underutilized potential for tackling Indonesia’s diverse environmental challenges by supporting investigations of groundwater contamination, water infiltration, and the accumulation of metals in soils and crops—issues crucial for agriculture, public health, and sustainable land management. Emerging technologies such as UAV-assisted imaging, airborne surveys, and oceanographic geophysical observations further demonstrate the flexibility of modern geophysics in studying coastal processes, wave behaviour, and coral reef conditions. However, its application—especially in urban Indonesia—remains limited due to physical obstructions, cultural noise, restricted workspace, regulatory hurdles, and safety concerns, while the absence of geophysical test sites (GTS) and a shortage of skilled practitioners constrain methodological advancement and training. Based on bibliometric analysis of Scopus-indexed publications, this study shows that integration between geophysics and environmental science is growing but still insufficient. Strengthening environmental geophysics in Indonesia requires developing dedicated training and calibration facilities, fostering interdisciplinary collaboration, and adopting technological innovations tailored to dense urban and complex geological settings so that geophysics can play a more effective role in environmental monitoring, resource sustainability, and resilience to ecological and urban challenges.

Tidal Hydrodynamics along Gulf of Khambhat, West Coast of India

Studies on coastal hydrodynamics and sediment transport help to unravel the coastal processes and facilitate formulation of shoreline management plans. An integrated approach which includes, extensive field data collection and numerical modelling is lacking along most of the coasts around the world, particularly along Indian coasts. The coastal stretch from Beypore to Puthiyappa, southwest coast of India has been selected for this present investigation. Harbour breakwaters in the northern and southern boundary of the study region have major impacts on shoreline modifications along this sector. In addition, a small harbour and associated breakwaters are located in the middle of the study region. Seawalls, and combination of seawall and smaller groins are constructed at many places as part of coastal protection. Sediment transport along the coast was computed with LITDRIFT model and the results show net northerly drift of 1.5 * 105 m3/year. The model results are comparable with the quantity of beach sediment mined from Puthiyappa beach (approximately of 0.8 * 105 m3/year). In addition, illegal mining is carried out in the region. Further, the model computed the shoreline evolution along the sector and major accumulation occurs south of Puthiyappa breakwater. Sand deposition close to groins and breakwaters along the study region support the model results. No further intervention along this sector is required for shore protection except, the maintenance of the existing protective measures such as seawalls and groins.

Effect of bottom friction on tidal hydrodynamics along Gulf of Khambhat, India