Harshinie Karunarathna

Swansea University | SWAN · Department of Civil Engineering

Abstract Laboratory experiments were conducted to explore the wave trains generated by vertical bed movements. The investigation consisted of 32 cases, involving four different water depths with unimodal and bimodal bed movements. Water surface displacement was measured using gauges positioned along a 30m long tank. A PIV system was set up to provi...

The numerical simulation of two-phase flow with Navier-Stokes equations is often hampered by the instabilities rises across the interface of the different fluids. The interfacial gradient of velocity and density leads to the unphysical momentum change, resulting in an ill-defined velocity field and twisted interface. To deal with this problem, we d...

Numerical modelling in the coastal environment often requires highly skilled users and can be hindered by high computation costs and time requirements. Machine Learning (ML) techniques have the potential to overcome these limitations and complement existing methods. This is an exploratory investigation utilising a Gaussian Process (GP) data-driven...

Saltmarshes in most estuaries in the UK and elsewhere are heavily exploited for numerous purposes including farming, fishing, and recreation. In this study, a computational model was used to investigate the impact of saltmarsh vegetation on tidal dynamics and residual currents in three distinctly different estuaries in Wales, UK, in order to unders...

Beach morphological states evolve over different time scales in relation to waves and antecedent beach characteristics. There are various forms of beach state which include dissipative, reflective, and intermediate. The aim of this work is to develop a new empirical model that can recognize beach state variability when beaches respond to varying wa...

The paper investigates compound flooding from waves, sea surge and river flow in northern Jakarta, Indonesia, which is a global hotspot of flooding, by combining process-based coastal and river models. The coastal hydrodynamic modelling of Jakarta Bay in Indonesia shows that coastal storms can lead to a substantial increase in sea water level due t...

Gravel barrier beaches can offer natural protection to coastlines from adverse storm conditions. Understanding the morphodynamics of gravel barrier beaches is vital for the effective and sustainable management of these systems. Here, we use a synthetic dataset to investigate the morphodynamic response of the gravel barrier beach at Hurst Castle Spi...

Habitat suitability modelling (HSM) is a tool that is increasingly being used to help guide decision making for conservation management. It can also be used to focus efforts of restoration in our oceans. To improve on model performance, the best available environmental data along with species distribution data are needed. Marine habitats tend to ha...

Tidal flows are seldom exactly sinusoidal, leading to a small discrepancy, or residual, over each tidal cycle. Although residuals are generally small in comparison with instantaneous currents, their cumulative effect is important for sediment transport and dispersion of contaminants. The meso-scale characteristics of tidal residual currents are inv...

As storm-driven coastal flooding increases under climate change, wetlands such as saltmarshes are held as a nature-based solution. Yet evidence supporting wetlands’ storm protection role in estuaries - where both waves and upstream surge drive coastal flooding - remains scarce. Here we address this gap using numerical hydrodynamic models within eig...

It is acknowledged that for successful mitigation of flood risk there is a need for an integrated, basin-wide approach. This is particularly important in transboundary river basins that cross administrative borders where the actions of multiple stakeholders must be coordinated from source to mouth. The Ciliwung River, Indonesia, presents an example...

As storm-driven coastal flooding increases under climate change, wetlands such as saltmarshes are held as a nature-based solution. Yet evidence supporting wetlands’ storm protection role in estuaries - where both waves and upstream surge drive coastal flooding - remains scarce. Here we address this gap using numerical hydrodynamic models within eig...

A computational model has been used to explore characteristics of the barotropic tide around the Welsh coast in detail for the first time. Proper understanding of tidal characteristics is vital for the sustainable use of marine resources; particularly for industries such as marine energy extraction, aggregate mining, aquaculture, as well as regulat...

Gravel beaches and barriers form a valuable natural protection for many shorelines. The paper presents a numerical modelling study of gravel barrier beach response to storm wave conditions. The XBeach non-hydrostatic model was set up in 1D mode to investigate barrier volume change and overwash under a wide range of unimodal and bimodal storm condit...

A new semi-analytical solution to the one-line model is presented in this work which can be used for the description of complicated coastal systems. An application of the semi-analytical model to Borth case study in Wales, UK, is presented. Additionally, Calangute beach in Goa, India, will be discussed as a future case study where the model will be...

“The aim of this article is to provide an introductory review on coastal engineering, emphasizing beach and shore protection. It is intended as a reference guide to a senior undergraduate or early career researcher who wants to pursue the topic to understand it at more than a superficial level. A brief history of the development of coastal engineer...

The ability of coastal vegetation to attenuate waves has been well established (Moller et al., 2014). Salt marshes are vegetated coastal wetlands that can act as nature- based coastal defenses. They exhibit a range of plant species, which have been shown to differ in the amount of wave damping they provide (Mullarney & Henderson, 2018). Recent stud...

Coastal vegetation such as seagrasses, salt marshes, and mangroves, contributes to coastal defence by damping incoming waves. Yet, plant species differ in flexibility due to which they interact differently with incoming waves and damp waves to a variable degree. Current wave damping models struggle to balance accuracy against computational costs wh...

Coastal dunes have global importance as ecological habitats, recreational areas, and vital natural coastal protection. Dunes evolve due to variations in the supply and removal of sediment via both wind and waves, and on stabilization through vegetation colonization and growth. One aspect of dune evolution that is poorly understood is the longshore...

Reduction of risks due to overtopping of coastal defences is an essential requirement for the design, management and adaptation of coastal structures. Extensive knowledge is available on the prediction of overtopping of smooth, sloping and vertical impermeable seawalls. The existing prediction methods provide less certain guidance for combined wind...

Turbulent flow over stepped spillways can be considered the most significant flow that can cause severe problems at the downstream side, near the toe of the structure, such as sediment erosion which normally occurs due to the high amount of water energy. The presence of turbulent flow over the steps can cause cavitation damages due to pressure diff...

The direct south-west swell wave approach and relatively narrow continental shelf create more favorable conditions for wave energy harvesting in Sri Lankan coastal region. South coast of Sri Lanka has the most energetic ocean waves which are highly modulated by the south-west monsoon winds. In this study, numerically projected ocean waves simulated...

This study investigates the impacts of global climate change on the future wave power potential, taking Sri Lanka as a case study from the northern Indian Ocean. The geographical location of Sri Lanka, which receives long-distance swell waves generated in the Southern Indian Ocean, favors wave energy-harvesting. Waves projected by a numerical wave...

Saltmarshes are considered as natural coastal defences. However, owing to the large context dependency, there is much discussion over their effectiveness in providing coastal protection and the necessity of additional coastal defence interventions. The macro-tidal Taf Estuary in south-west Wales was chosen as the case study in this paper to investi...

Vegetation can contribute to coastal defence by damping incoming waves. However, prior studies have shown that attenuation varies greatly among plant species. Plant flexibility is a mechanical property that is commonly omitted, but varies considerably between shrubs and grasses on salt marshes. Therefore, we present an experimental study in a labor...

The paper presents a detailed analysis of the spatio-temporal variability of wave power resource around Sri Lanka, using computationally simulated 25 years of wave data that represents the prevailing ocean climate in the region. The computational wave model was validated against a measured wave dataset collected over a 44-month period at 70 m water...

Understanding of the reflection characteristics of coastal seawalls is crucial for design. Wave reflection can cause difficulties in small vessel manoeuvring at harbour entrances; this can cause damage to the toe of coastal structures by scouring. Previous studies have examined the reflection characteristics of coastal seawalls under random wind-ge...

Beach profile evolution under storm sequence forcing presents an emerging research topic that has only been investigated at a limited number of sites. The occurrence and effects of storm sequencing on beach profile evolution are studied at Hasaki Beach, Japan, using weekly beach profile and two-hourly offshore wave measurements. During the 25-year...

Better understanding of the global wave climate is required to inform wave energy device design and large-scale deployment. Spatial variability in the global wave climate is analysed here to provide a range of characteristic design wave climates. K-means clustering was used to split the global wave resource into 6 classes in a device agnostic, data...

Understanding of reflection characteristics of coastal seawalls is crucial for design. Wave reflection can cause difficulties to small vessel manoeuvring at the harbour entrance and constitute damaging scouring at the toe of coastal structures. Previous studies have considered reflection characteristics of coastal seawalls under wind-generated rand...

Being an island surrounded by the ocean, a significant potential exists in Sri Lanka to harness ocean wave energy as a renewable energy source. The assessment of wave energy characteristics in coastal waters of Sri Lanka is important in identifying such a potential. A detailed analysis of patio-temporal variability of wave power was carried out by...

Prediction of wave overtopping is a crucial component of coastal structure and seawall designs. Modelling efforts have improved coastal seawall construction design and have saved construction costs. Despite a large amount of research on wave overtopping as published in the EurOtop (2018), there are still knowledge gaps to be considered in terms of...

Global climate change drives sea level rise and changes to extreme weather events, which can affect morphodynamics of coastal and estuary systems around the world. In this paper, a 2D process-based numerical model is used to investigate the combined effects of future mean sea level and storm climate variabilities on morphological change of an estua...

Purpose Coastal flooding has disastrous consequences on people, infrastructure, properties and the environment. Increasing flood risk as a result of global climate change is a significant concern both within the UK and globally. To counter any potential increase in future flooding, a range of potential management options are being considered. This...

The use of saltmarshes as an intervention to alleviate the effects of coastal flooding has gained increasing intention due to climate change. A coupled Delft3D FLOW-WAVE model was developed for the macrotidal Taf estuary in South West Wales to assess how three different interventions on saltmarsh management affected coastal flooding. An extreme sto...

This paper reviews and discusses the current research status, trends, and future needs in the field of beach morphodynamics under the influence of storm sequences. The paper reviews how the three main research methods, field investigations, numerical modelling, and physical modelling, have been used to study beach morphodynamics during storm sequen...

Salt marshes are coastal wetlands that can reduce flood risk by their vegetation. The drag that salt marsh plants induces on currents modifies estuary hydrodynamics which affects flood water levels, surge propagation and sediment transport. Four parameterisations to model the drag by vegetation on currents have been proposed in literature: (i) a fi...

The tidal energy sector is a growing industry in the UK and beyond. Energy developers’ interests are progressing towards the deployment of large arrays of tidal energy converters (TECs). Numerous factors will affect decision making related to arrays siting and size. One key factor is the effect that the TEC arrays may have on the natural sediment t...

Tsunamis are among the most destructive natural hazards and can cause massive damage to the coastal communities. This paper presents a first numerical study on the tsunami-like solitary wave impinging and overtopping based on the mesh-free Consistent Particle Method (CPM). The distinct feature of CPM is that it computes the spatial derivatives in a...

The twin ambits of climate change and coastal development have raised public awareness of shoreline management. Simultaneously, they have highlighted a gap in our understanding of sediment transport and morphodynamic processes at time and space scales appropriate for shoreline management purposes. Here, we analyse an exceptional set of beach survey...

Global climate variabilities have the potential to impact many coastlines around the world, and can have detrimental effects on the stability of coastlines and their function as natural coastal defenses. This paper investigates the impacts of future extreme storms and sea level rise on morphodynamics of the macro-tidal Sefton Coast, UK, taking a pr...

The tidal energy sector attracts developers' interest worldwide. For potential tidal energy deployment sites, numerous factors will impact decision making process related to siting and size of the tidal energy converter (TEC) farms. A key factor is the effect that TECs may have on the natural coastal hydrodynamic and morpho-dynamic environment. In...

Over recent years, there has been a clear increase in the frequency of reported flooding events around the world. Gabion structures offer one means of flood mitigation in dam spillways. These types of structures provide an additional challenge to the computational modeller in that flow through the porous gabions must be simulated. We have used a co...

This paper presents the results of a sensitivity study investigating beach/dune response to offshore wave boundary forcing. The modelling study was based on the convex-shape Sefton coast, UK which has a complex nearshore morphology and foreshore frontal dunes. Simulations were performed using a cascade of nested grids to transform offshore waves up...

Salt marshes are vegetated tidal wetlands, which can typically be found at sheltered coastal areas in moderate climate zones. Their potential as natural coastal protection by wave attenuation (Möller et al, 2014), reduction of flood-surge propagation (Stark et al., 2016) and shoreline stabilization (Bouma et al, 2014) has been increasingly recogniz...

Bimodal seas are usually characterised by the combination of swell and locally generated wind energy. Understanding the percentage of the swell component (SC) and the wind component (WC) partitioned from the energy content of a Wave System (WS) is important in coastal defense design and management. The South Wales and southwest England wave climate...

As anthropogenic use of the coastal zone diversifies, for example marine energy extraction, the coastal environments of interest to coastal engineers and managers is becoming more varied. Increasingly, the morphodynamics of geomorphologically complex, mixed sediment and geologically constrained beaches are important. Even in areas where erosion and...

The Severn Estuary (west coast of UK) is a highly dynamic environment and thus understanding of sediment transport under both natural and man-made changes is vital to the sustainable use of the coastal area in this region. The area is likely to be the site of the world’s first tidal energy lagoon. The construction and operation of the lagoon will r...

Tidal inlets, a common feature along coastlines globally, can be significantly affected by the impacts of global climate variabilities. Computational models provide the best opportunity to assess future changes to the dynamics of inlet systems. In this paper, the morphodynamic response of a gravel-dominated meso-tidal estuary inlet to Sea Level Ris...

This paper presents an analysis of wave recordings with particular attention to assessing bimodality of the incident wave energy spectra and the occurrence of swell along the south and south-west coasts of the United Kingdom, (UK). A procedure is developed to perform an intensive analysis of a new and large dataset of measured wave spectra. A storm...

Medium/long term trends (annual to decadal scale) of beach change are mostly used to make coastal management decisions. However, short term, extreme episodic events (short term) can erode the beach to exceed sustainable erosion thresholds thereby impacting long term trends of coastal change. Therefore, understanding coastal change at short and medi...

Using the PIV technique to measure the velocity profiles over gabion stepped spillways and normal stepped spillways under dam break conditions.

Extraction of energy from tidal streams has the potential to impact on the morphodynamics of areas such as sub-tidal sandbanks via alteration of hydrodynamics. Marine sediment transport is forced by both wave and tidal currents. Past work on tidal stream turbine impacts has largely ignored the contribution of waves. Here, a fully coupled hydrodynam...

The work presents a methodology to assess the coastal impacts during a storm event which caused significant damage along the promenade at Aberystwyth, Wales on the 3 January 2014. Overtopping was analysed in detail for a section of promenade by downscaling offshore wave conditions to force a surf zone hydrodynamic model, NEWRANS. Overtopping discha...

Energy dissipation is one of the most important issues in spillway design as the downstream water flow can be highly energetic, which may lead to the creation of a scour hole in the downstream region. As a means of dissipating energy, stepped spillways can be used. The presence of steps can generate greater flow turbulence dissipating more energy t...

Future storm impacts on dune evolution due to changing storm frequency were simulated in XBeach at an exemplary dune system, Formby Point, UK. Probabilistic approaches were used to establish the future storm clusters from 2015 to 2065 in three scenarios, using measured data in Liverpool Bay. Cross-shore profile simulations were carried out in two s...

The purpose of this work was to develop a computational process to investigate the effect of bimodal wave conditions on wave overtopping. The numerical model NEWRANS has been validated for the application of bimodal wave overtopping and a procedure developed to generate the desired wave conditions in the flume. When applied to bi-modal specific wav...