In this paper we describe the application of Canonical Correlation Analysis (CCA) to an historica... more In this paper we describe the application of Canonical Correlation Analysis (CCA) to an historical dataset of seabed elevations within a coastal segment of the English south eastern coast. The study site is located along the frontage of Walcott (Norfolk, East coast of England). The beaches along this segment of coast are mainly composite, mixed sand and shingle. The dataset comprises detailed bathymetric surveys of beach profiles covering a period of over 17 years (~ 2 beach profile surveys every year). The structure of the dataset and the data handling methods are described. The application of the CCA method is discussed as well as the ability of the CCA to provide useful forecast of the beach profile at Walcott. Some results and interpretation of the analysis are presented. Beach profiles predictions agreed well with the measured profiles for up to five years of forecast at the site. The level of error using CCA is proportionate with that found with dynamical modelling. It is expected that this relationship will be used by coastal planners to predict profile evolution based on waves and storm surges.
Longshore sediment transport is an important nearshore process that governs coastal erosion/accre... more Longshore sediment transport is an important nearshore process that governs coastal erosion/accretion and in turn, defines the orientation of coastlines. In this study, we assess the changes in longshore transport rates along the Indian coast due to the potential changes in wave parameters under the RCP4.5 climate scenario. The projected wave climate for two time slices, "near-term/present" (2011-2040) and "mid-term/future" (2041-2070) were used to investigate changes in the corresponding sediment transport rates. An empirical model accounting for major wave parameters, longshore current, resulting sediment transport, and shoreline evolution, was used. It was found that most of the Indian coast exhibited the same drift direction in both time slices, although changes in transport magnitude were present. To give a broadbrush characterisation of the coastline, the shoreline elements were classified as erosive, accretive or stable based on the comparative longshore transport rates of neighbouring elements. Similar characterisations, carried out for both time slices showed that about 35% of the total coastline would remain unaffected due to the changing wave climate in future (i.e. there is little to no change); about 20% is expected to "worsen" (i.e. expected to undergo higher magnitudes of erosion wrt present rate); and 45% to "improve" (i.e. expected to accrete/reach stability). It was also observed that the net annual transport rates pertaining to the future period are not expected to change significantly with respect to the current scenario. This indicates that the change in longshore transport rates arising from future changes in wave climate as represented by the RCP4.5 climate change scenario will have a broadly neutral effect.
Journal Of Geophysical Research: Earth Surface, Mar 1, 2021
The response of marine-terminating glaciers to oceanic forcing is one of the major unknowns in pr... more The response of marine-terminating glaciers to oceanic forcing is one of the major unknowns in predicting the future response of the Greenland ice sheet to climate change (Church et al., 2013). One of the key reasons for this uncertainty is our limited understanding of processes occurring in the ice-ocean boundary layer (Straneo & Cenedese, 2015). In this region, processes on the order of meters and centimeters drive melt rates which influence larger-scale processes such as calving, ice dynamics, and fjord circulation (Car
This study investigates the freak wave impinging on a tension-leg platform through wave flume exp... more This study investigates the freak wave impinging on a tension-leg platform through wave flume experiments. The freak waves are generated using the focused wave theory. By adjusting the wave focusing location, different incident wave scenarios at the structure location are produced. Simultaneous measurements of wave shape evolutions upon impingement, wave impact pressures on the platform deck, platform motions and tether forces are carried out for synchronized analyses of the wave kinematics/dynamics and structural responses. The variation of these parameters with the incident wave profile is studied. It is found that although applying less intensive local impact pressures as compared to the highly-breaking freak wave, the slightly-breaking or non-breaking freak wave imposes the same level of adverse effect on the platform's global stability in terms of motions and tether forces. In addition, the high-crest freak wave causes violent motions of the floating platform, which are likely to induce snap loads of large amplitude and high occurrence frequency in tethers. The published results would provide useful benchmarks for validating numerical and analytical models.
Crown heights of seawalls should be designed to suppress overtopping discharge to a permissible l... more Crown heights of seawalls should be designed to suppress overtopping discharge to a permissible level. The permissible level is determined from viewpoints of the structure types of coastal seawalls and hinterland use. It is usually difficult to design the crown heights of seawalls, especially in the present time where climate change due to global warming is expected. This study analyzes climate change effects such as sea level rise (SLR) and increase of waves and surges on the failure probability of seawalls under various conditions of crown height, toe depth and slope by using a Level III reliability analysis. It was found that the difference of SLR trends (fast, medium or low) has less impact on overtopping rates than the differences in wave height change for a seawall at a target location.
Engineering Analysis With Boundary Elements, Jun 1, 2019
Tsunamis are among the most destructive natural hazards and can cause massive damage to the coast... more 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 way consistent with the Taylor series expansion and hence achieves good numerical consistency and accuracy. This largely alleviates the spurious pressure fluctuation that is a key issue for the particle method. Validated by the benchmark example of solitary wave impact on a seawall, the CPM model is shown to be able to capture the highly deformed breaking wave and the impact pressure associated with wave impinging and overtopping. Using the numerical model, a parametric study of the effect of seawall cross-sectional geometry on the characteristics of wave overtopping is conducted. It is found that a higher water level can lead to much more intensive overtopping volume and kinetic energy of the overtopping flow, which implies that the coastal areas are at higher risk as the sea level rises. For the purpose of engineering interest, a simple and practical way to estimate the intensity of a real tsunami is presented in terms of the volume and energy of the bulge part of the incident wave.
international journal of energy and environmental engineering, Sep 2, 2022
Marine renewable energy site and resource characterisation, in particular tidal stream energy, re... more Marine renewable energy site and resource characterisation, in particular tidal stream energy, require detailed flow measurements which often rely on high-cost in situ instrumentation which is limited in spatial extent. We hypothesise uncrewed aerial vehicles (UAV) offer a low-cost and low-risk data collection method for tidal stream environments, as recently techniques have been developed to derive flow from optical videography. This may benefit tidal and floating renewable energy developments, providing additional insight into flow conditions and complement traditional instrumentation. Benefits to existing data collection methods include capturing flow over a large spatial extent synchronously, which could be used to analyse flow around structures or for site characterisation; however, uncertainty and method application to tidal energy sites is unclear. Here, two algorithms are tested: large-scale particle image velocimetry using PIVlab and dense optical flow. The methods are applied on video data collected at two tidal stream energy sites (Pentland Firth, Scotland, and Ramsey Sound, Wales) for a range of flow and environmental conditions. Although average validation measures were similar (~ 20-30% error), we recommend PIVlab processed velocity data at tidal energy sites because we find bias (underprediction) in optical flow for higher velocities (> 1 m/s).
Longshore sediment transport is an important nearshore process that governs coastal erosion/accre... more Longshore sediment transport is an important nearshore process that governs coastal erosion/accretion and in turn, defines the orientation of coastlines. In this study, we assess the changes in longshore transport rates along the Indian coast due to the potential changes in wave parameters under the RCP4.5 climate scenario. The projected wave climate for two time slices, "near-term/present" (2011-2040) and "mid-term/future" (2041-2070) were used to investigate changes in the corresponding sediment transport rates. An empirical model accounting for major wave parameters, longshore current, resulting sediment transport, and shoreline evolution, was used. It was found that most of the Indian coast exhibited the same drift direction in both time slices, although changes in transport magnitude were present. To give a broadbrush characterisation of the coastline, the shoreline elements were classified as erosive, accretive or stable based on the comparative longshore transport rates of neighbouring elements. Similar characterisations, carried out for both time slices showed that about 35% of the total coastline would remain unaffected due to the changing wave climate in future (i.e. there is little to no change); about 20% is expected to "worsen" (i.e. expected to undergo higher magnitudes of erosion wrt present rate); and 45% to "improve" (i.e. expected to accrete/reach stability). It was also observed that the net annual transport rates pertaining to the future period are not expected to change significantly with respect to the current scenario. This indicates that the change in longshore transport rates arising from future changes in wave climate as represented by the RCP4.5 climate change scenario will have a broadly neutral effect.
Vegetation can contribute to coastal defence by damping incoming waves. However, prior studies ha... more 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 laboratory wave flume with artificial vegetation that differs in flexibility only. We measured wave attenuation and water particle velocities around rigid and flexible salt marsh vegetation. Waves were measured using a series of gauges and Particle Image Velocimetry (PIV) was used to measure spatio-temporal variations of water particle velocities in the x-z plane around the vegetation. Our results show that flexible vegetation attenuates waves up to 70% less than rigid vegetation due to swaying of flexible plants. Furthermore, we find that rigid vegetation modifies the velocity structure, whereas flexible vegetation does not. Specifically, a mean current in the direction of wave propagation develops around the canopy and the horizontal particle velocities are amplified directly above the canopy. These results indicate that plant flexibility is a key parameter in the wave-vegetation interaction that controls wave damping and velocity structure.
The tidal energy sector is a growing industry in the UK and beyond. Energy developers' interests ... more 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 transport patterns and the sea bottom morphodynamics. The Inner Sound Channel located between the Island of Stroma of Pentland Firth and the Scottish Mainland (UK) has been accredited for a large-scale TEC array installation to be developed in the future. Three morphodynamically active, large sandbanks are located in the Inner Sound channel. This study investigated the impacts of tidal energy extraction from a large array of TECs on the sediment dynamics and morphology of these sandbanks. A large-scale 3D hydrodynamic and morphodynamic Delft3D model was set up to computationally model Pentland Firth, Inner Sound Channel in order to study the impacts of tidal energy extraction from a generic TEC array, on the existing hydrodynamic and morphodynamic regime. A range of hypothetical energy extraction scenarios was modelled. Results reveal that the changes to morphodynamics of these sandbanks as a result of large scale tidal energy extraction far exceeds the morphology change under the natural hydrodynamic regime and that the severity of morphology change depends on the level of energy extraction.
Abstract A statisticaldynamical model for estuary mor-phodynamics is presented and demonstrated ... more Abstract A statisticaldynamical model for estuary mor-phodynamics is presented and demonstrated with a case study on the Humber Estuary, UK. The model presented here is hybrid in nature where simplified process dynamics are combined with a data-driven approach. The modelling ...
... The dataset employed in this work was collected during a laboratory investigation of gravel a... more ... The dataset employed in this work was collected during a laboratory investigation of gravel and mixed sand and gravel beaches completed in May 2002 at the Large Wave Flume (GWK) of the Coastal Research Centre in Hanover, Germany (López de San Roman-Blanco et al ...
Offshore sandbanks provide a major source of sediment and may have a significant impact on the ev... more Offshore sandbanks provide a major source of sediment and may have a significant impact on the evolution of the nearby shoreline. The prediction of sandbank evolution is extremely important for coastal engineers and managers. However, it is evident from the existing literature that ...
According to VPN, after the training wall construction, there was substantial accumulation of sal... more According to VPN, after the training wall construction, there was substantial accumulation of salt marshes and sand banks.[...] we would like to reemphasise that the main novelty within our paper is not the geomorphological rules per se but the development of a mathematically ...
In this paper we describe the application of Canonical Correlation Analysis (CCA) to an historica... more In this paper we describe the application of Canonical Correlation Analysis (CCA) to an historical dataset of seabed elevations within a coastal segment of the English south eastern coast. The study site is located along the frontage of Walcott (Norfolk, East coast of England). The beaches along this segment of coast are mainly composite, mixed sand and shingle. The dataset comprises detailed bathymetric surveys of beach profiles covering a period of over 17 years (~ 2 beach profile surveys every year). The structure of the dataset and the data handling methods are described. The application of the CCA method is discussed as well as the ability of the CCA to provide useful forecast of the beach profile at Walcott. Some results and interpretation of the analysis are presented. Beach profiles predictions agreed well with the measured profiles for up to five years of forecast at the site. The level of error using CCA is proportionate with that found with dynamical modelling. It is expected that this relationship will be used by coastal planners to predict profile evolution based on waves and storm surges.
Longshore sediment transport is an important nearshore process that governs coastal erosion/accre... more Longshore sediment transport is an important nearshore process that governs coastal erosion/accretion and in turn, defines the orientation of coastlines. In this study, we assess the changes in longshore transport rates along the Indian coast due to the potential changes in wave parameters under the RCP4.5 climate scenario. The projected wave climate for two time slices, "near-term/present" (2011-2040) and "mid-term/future" (2041-2070) were used to investigate changes in the corresponding sediment transport rates. An empirical model accounting for major wave parameters, longshore current, resulting sediment transport, and shoreline evolution, was used. It was found that most of the Indian coast exhibited the same drift direction in both time slices, although changes in transport magnitude were present. To give a broadbrush characterisation of the coastline, the shoreline elements were classified as erosive, accretive or stable based on the comparative longshore transport rates of neighbouring elements. Similar characterisations, carried out for both time slices showed that about 35% of the total coastline would remain unaffected due to the changing wave climate in future (i.e. there is little to no change); about 20% is expected to "worsen" (i.e. expected to undergo higher magnitudes of erosion wrt present rate); and 45% to "improve" (i.e. expected to accrete/reach stability). It was also observed that the net annual transport rates pertaining to the future period are not expected to change significantly with respect to the current scenario. This indicates that the change in longshore transport rates arising from future changes in wave climate as represented by the RCP4.5 climate change scenario will have a broadly neutral effect.
Journal Of Geophysical Research: Earth Surface, Mar 1, 2021
The response of marine-terminating glaciers to oceanic forcing is one of the major unknowns in pr... more The response of marine-terminating glaciers to oceanic forcing is one of the major unknowns in predicting the future response of the Greenland ice sheet to climate change (Church et al., 2013). One of the key reasons for this uncertainty is our limited understanding of processes occurring in the ice-ocean boundary layer (Straneo & Cenedese, 2015). In this region, processes on the order of meters and centimeters drive melt rates which influence larger-scale processes such as calving, ice dynamics, and fjord circulation (Car
This study investigates the freak wave impinging on a tension-leg platform through wave flume exp... more This study investigates the freak wave impinging on a tension-leg platform through wave flume experiments. The freak waves are generated using the focused wave theory. By adjusting the wave focusing location, different incident wave scenarios at the structure location are produced. Simultaneous measurements of wave shape evolutions upon impingement, wave impact pressures on the platform deck, platform motions and tether forces are carried out for synchronized analyses of the wave kinematics/dynamics and structural responses. The variation of these parameters with the incident wave profile is studied. It is found that although applying less intensive local impact pressures as compared to the highly-breaking freak wave, the slightly-breaking or non-breaking freak wave imposes the same level of adverse effect on the platform's global stability in terms of motions and tether forces. In addition, the high-crest freak wave causes violent motions of the floating platform, which are likely to induce snap loads of large amplitude and high occurrence frequency in tethers. The published results would provide useful benchmarks for validating numerical and analytical models.
Crown heights of seawalls should be designed to suppress overtopping discharge to a permissible l... more Crown heights of seawalls should be designed to suppress overtopping discharge to a permissible level. The permissible level is determined from viewpoints of the structure types of coastal seawalls and hinterland use. It is usually difficult to design the crown heights of seawalls, especially in the present time where climate change due to global warming is expected. This study analyzes climate change effects such as sea level rise (SLR) and increase of waves and surges on the failure probability of seawalls under various conditions of crown height, toe depth and slope by using a Level III reliability analysis. It was found that the difference of SLR trends (fast, medium or low) has less impact on overtopping rates than the differences in wave height change for a seawall at a target location.
Engineering Analysis With Boundary Elements, Jun 1, 2019
Tsunamis are among the most destructive natural hazards and can cause massive damage to the coast... more 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 way consistent with the Taylor series expansion and hence achieves good numerical consistency and accuracy. This largely alleviates the spurious pressure fluctuation that is a key issue for the particle method. Validated by the benchmark example of solitary wave impact on a seawall, the CPM model is shown to be able to capture the highly deformed breaking wave and the impact pressure associated with wave impinging and overtopping. Using the numerical model, a parametric study of the effect of seawall cross-sectional geometry on the characteristics of wave overtopping is conducted. It is found that a higher water level can lead to much more intensive overtopping volume and kinetic energy of the overtopping flow, which implies that the coastal areas are at higher risk as the sea level rises. For the purpose of engineering interest, a simple and practical way to estimate the intensity of a real tsunami is presented in terms of the volume and energy of the bulge part of the incident wave.
international journal of energy and environmental engineering, Sep 2, 2022
Marine renewable energy site and resource characterisation, in particular tidal stream energy, re... more Marine renewable energy site and resource characterisation, in particular tidal stream energy, require detailed flow measurements which often rely on high-cost in situ instrumentation which is limited in spatial extent. We hypothesise uncrewed aerial vehicles (UAV) offer a low-cost and low-risk data collection method for tidal stream environments, as recently techniques have been developed to derive flow from optical videography. This may benefit tidal and floating renewable energy developments, providing additional insight into flow conditions and complement traditional instrumentation. Benefits to existing data collection methods include capturing flow over a large spatial extent synchronously, which could be used to analyse flow around structures or for site characterisation; however, uncertainty and method application to tidal energy sites is unclear. Here, two algorithms are tested: large-scale particle image velocimetry using PIVlab and dense optical flow. The methods are applied on video data collected at two tidal stream energy sites (Pentland Firth, Scotland, and Ramsey Sound, Wales) for a range of flow and environmental conditions. Although average validation measures were similar (~ 20-30% error), we recommend PIVlab processed velocity data at tidal energy sites because we find bias (underprediction) in optical flow for higher velocities (> 1 m/s).
Longshore sediment transport is an important nearshore process that governs coastal erosion/accre... more Longshore sediment transport is an important nearshore process that governs coastal erosion/accretion and in turn, defines the orientation of coastlines. In this study, we assess the changes in longshore transport rates along the Indian coast due to the potential changes in wave parameters under the RCP4.5 climate scenario. The projected wave climate for two time slices, "near-term/present" (2011-2040) and "mid-term/future" (2041-2070) were used to investigate changes in the corresponding sediment transport rates. An empirical model accounting for major wave parameters, longshore current, resulting sediment transport, and shoreline evolution, was used. It was found that most of the Indian coast exhibited the same drift direction in both time slices, although changes in transport magnitude were present. To give a broadbrush characterisation of the coastline, the shoreline elements were classified as erosive, accretive or stable based on the comparative longshore transport rates of neighbouring elements. Similar characterisations, carried out for both time slices showed that about 35% of the total coastline would remain unaffected due to the changing wave climate in future (i.e. there is little to no change); about 20% is expected to "worsen" (i.e. expected to undergo higher magnitudes of erosion wrt present rate); and 45% to "improve" (i.e. expected to accrete/reach stability). It was also observed that the net annual transport rates pertaining to the future period are not expected to change significantly with respect to the current scenario. This indicates that the change in longshore transport rates arising from future changes in wave climate as represented by the RCP4.5 climate change scenario will have a broadly neutral effect.
Vegetation can contribute to coastal defence by damping incoming waves. However, prior studies ha... more 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 laboratory wave flume with artificial vegetation that differs in flexibility only. We measured wave attenuation and water particle velocities around rigid and flexible salt marsh vegetation. Waves were measured using a series of gauges and Particle Image Velocimetry (PIV) was used to measure spatio-temporal variations of water particle velocities in the x-z plane around the vegetation. Our results show that flexible vegetation attenuates waves up to 70% less than rigid vegetation due to swaying of flexible plants. Furthermore, we find that rigid vegetation modifies the velocity structure, whereas flexible vegetation does not. Specifically, a mean current in the direction of wave propagation develops around the canopy and the horizontal particle velocities are amplified directly above the canopy. These results indicate that plant flexibility is a key parameter in the wave-vegetation interaction that controls wave damping and velocity structure.
The tidal energy sector is a growing industry in the UK and beyond. Energy developers' interests ... more 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 transport patterns and the sea bottom morphodynamics. The Inner Sound Channel located between the Island of Stroma of Pentland Firth and the Scottish Mainland (UK) has been accredited for a large-scale TEC array installation to be developed in the future. Three morphodynamically active, large sandbanks are located in the Inner Sound channel. This study investigated the impacts of tidal energy extraction from a large array of TECs on the sediment dynamics and morphology of these sandbanks. A large-scale 3D hydrodynamic and morphodynamic Delft3D model was set up to computationally model Pentland Firth, Inner Sound Channel in order to study the impacts of tidal energy extraction from a generic TEC array, on the existing hydrodynamic and morphodynamic regime. A range of hypothetical energy extraction scenarios was modelled. Results reveal that the changes to morphodynamics of these sandbanks as a result of large scale tidal energy extraction far exceeds the morphology change under the natural hydrodynamic regime and that the severity of morphology change depends on the level of energy extraction.
Abstract A statisticaldynamical model for estuary mor-phodynamics is presented and demonstrated ... more Abstract A statisticaldynamical model for estuary mor-phodynamics is presented and demonstrated with a case study on the Humber Estuary, UK. The model presented here is hybrid in nature where simplified process dynamics are combined with a data-driven approach. The modelling ...
... The dataset employed in this work was collected during a laboratory investigation of gravel a... more ... The dataset employed in this work was collected during a laboratory investigation of gravel and mixed sand and gravel beaches completed in May 2002 at the Large Wave Flume (GWK) of the Coastal Research Centre in Hanover, Germany (López de San Roman-Blanco et al ...
Offshore sandbanks provide a major source of sediment and may have a significant impact on the ev... more Offshore sandbanks provide a major source of sediment and may have a significant impact on the evolution of the nearby shoreline. The prediction of sandbank evolution is extremely important for coastal engineers and managers. However, it is evident from the existing literature that ...
According to VPN, after the training wall construction, there was substantial accumulation of sal... more According to VPN, after the training wall construction, there was substantial accumulation of salt marshes and sand banks.[...] we would like to reemphasise that the main novelty within our paper is not the geomorphological rules per se but the development of a mathematically ...
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Papers by Dominic Reeve