By analysing and comparing the results of post-disaster field studies and literature regarding th... more By analysing and comparing the results of post-disaster field studies and literature regarding the mechanisms by which coastal structures failed due to the 2004 Indian Ocean Tsunami and the 2011 Tohoku Tsunami events (the focus being on defence structures where applicable), trends were identified and examined. This paper highlights the most commonly occurring / major failure mechanisms identified in the various locations affected by the two tsunami events. The failure modes found in over twenty locations throughout the Fukushima, Iwate and Miyagi Prefectures of Japan were categorised into seven failure modes: a) leeward toe scour, b) crown armour failure, c) leeward armour failure, d) parapet wall failure, e) overturning, f) seaward toe scour, and g) sliding. Leeward toe scour was found to be the major failure mechanism in seawalls and dikes, and sliding was found to be the major failure mechanism in concrete breakwaters. The failure modes found throughout regions affected by the In...
The modelling of coastal morphodynamics has often been hindered by the lack of robustness/accurac... more The modelling of coastal morphodynamics has often been hindered by the lack of robustness/accuracy of constituent formulae, especially sediment transport formulae in the breaking and swash zones. Consequently, modellers are often forced to rely on crude calibration efforts and practical models consisting of empirical tuning-constants, to obtain favourable model results. Such methods are often unavoidable however due to theoretical limitations of existing models. The aim of this thesis is therefore to improve accuracy and applicability of suspended sand transport models for breaking wave conditions, for implementation into morphodynamic modelling studies. Several existing suspended sand transport models (6 reference concentration C₀ + 5 concentration profile C[z]) models were evaluated quantitatively and qualitatively against one another, and against state-of-the-art high-resolution datasets which were collected under large-scale breaking wave conditions. Numerous limitations were ob...
Process-based morphodynamic modelling suites (as well as other process-based models) are often co... more Process-based morphodynamic modelling suites (as well as other process-based models) are often considered to be inefficient and unsuitable for simulating medium- to long-term morphodynamics due to the various theoretical (e.g. robustness of sediment transport models) and practical (e.g. computational costs) limitations. In particular, a lack of knowledge of sediment transport processes and how they relate to hydrodynamics makes the application of short-term models to long-term coastal evolution challenging. Even the state-of-the-art coastal area modelling suites (such as Delft3D and MIKE21) consist of relatively simple physics, relying instead on numerous semi-empirical parameterizations, which are often poorly supported by measured data and/or physical process understanding. In particular, suspended sediment transport in the highly turbulent surf zone is poorly modelled under breaking wave conditions. Six existing suspended sand concentration (SSC) models were critically evaluated ...
Implementing the effects of turbulent kinetic energy (TKE) is essential in producing accurate sus... more Implementing the effects of turbulent kinetic energy (TKE) is essential in producing accurate suspended sediment concentration (SSC) models, especially under breaking wave conditions. SSC is commonly attributed to two different turbulent sources under breaking wave conditions: 1) bed-friction and 2) breaking-induced turbulent vortices. Numerous studies have endeavoured to quantify the effects of TKE and incorporate them into SSC models. To name a few: Mocke & Smith (1992, henceforth MS92), Shibayama & Rattanapitikon (1993, henceforth SR93), Jayaratne & Shibayama (2007, henceforth JS07), and Yoon et al. (2015, henceforth Y15). The present study evaluates these 4 existing SSC models and validates them against recently published datasets from the ‘CROSSTEX’ (Yoon & Cox, 2010), ‘SandT-Pro’ (Ribberink et al., 2014) and ‘SINBAD’ (vdZ et al. 2015) projects. Following critical evaluation, suggestions are made to enhance existing SSC models, and these findings are then incorporated into prod...
By analysing and comparing the results of post-disaster field studies and literature regarding th... more By analysing and comparing the results of post-disaster field studies and literature regarding the mechanisms by which coastal structures failed due to the 2004 Indian Ocean Tsunami and the 2011 Tohoku Tsunami events (the focus being on defence structures where applicable), trends were identified and examined. This paper highlights the most commonly occurring / major failure mechanisms identified in the various locations affected by the two tsunami events. The failure modes found in over twenty locations throughout the Fukushima, Iwate and Miyagi Prefectures of Japan were categorised into seven failure modes: a) leeward toe scour, b) crown armour failure, c) leeward armour failure, d) parapet wall failure, e) overturning, f) seaward toe scour, and g) sliding. Leeward toe scour was found to be the major failure mechanism in seawalls and dikes, and sliding was found to be the major failure mechanism in concrete breakwaters. The failure modes found throughout regions affected by the Indian Ocean Tsunami were categorised into five failure mechanisms: a) scouring of foundations, b) beam /column failure, c) joint failure, d) wall failure, and e) total disintegration. The 'total disintegration' caused by seismic forces, debris collision and hydrodynamic forces was the major failure mode throughout the studied regions. Some of the major tsunami induced forces found to have been among the causal factors of structural failure included hydrostatic and hydrodynamic forces. Flow velocities as high as 13.4 m/s were found in areas of Japan, and flow velocities of up to 10.4 m/s were found in regions affected by the 2004 Indian Ocean Tsunami. Potential strengthening measures were suggested for structures such as seawalls and coastal dikes, which were most vulnerable to scouring at the toe. By producing armoured components to protect the toe of the structures, they would become less susceptible to toe scour failure.
By analysing and comparing the results of post-disaster field studies and literature regarding th... more By analysing and comparing the results of post-disaster field studies and literature regarding the mechanisms by which coastal structures failed due to the 2004 Indian Ocean Tsunami and the 2011 Tohoku Tsunami events (the focus being on defence structures where applicable), trends were identified and examined. This paper highlights the most commonly occurring / major failure mechanisms identified in the various locations affected by the two tsunami events. The failure modes found in over twenty locations throughout the Fukushima, Iwate and Miyagi Prefectures of Japan were categorised into seven failure modes: a) leeward toe scour, b) crown armour failure, c) leeward armour failure, d) parapet wall failure, e) overturning, f) seaward toe scour, and g) sliding. Leeward toe scour was found to be the major failure mechanism in seawalls and dikes, and sliding was found to be the major failure mechanism in concrete breakwaters. The failure modes found throughout regions affected by the In...
The modelling of coastal morphodynamics has often been hindered by the lack of robustness/accurac... more The modelling of coastal morphodynamics has often been hindered by the lack of robustness/accuracy of constituent formulae, especially sediment transport formulae in the breaking and swash zones. Consequently, modellers are often forced to rely on crude calibration efforts and practical models consisting of empirical tuning-constants, to obtain favourable model results. Such methods are often unavoidable however due to theoretical limitations of existing models. The aim of this thesis is therefore to improve accuracy and applicability of suspended sand transport models for breaking wave conditions, for implementation into morphodynamic modelling studies. Several existing suspended sand transport models (6 reference concentration C₀ + 5 concentration profile C[z]) models were evaluated quantitatively and qualitatively against one another, and against state-of-the-art high-resolution datasets which were collected under large-scale breaking wave conditions. Numerous limitations were ob...
Process-based morphodynamic modelling suites (as well as other process-based models) are often co... more Process-based morphodynamic modelling suites (as well as other process-based models) are often considered to be inefficient and unsuitable for simulating medium- to long-term morphodynamics due to the various theoretical (e.g. robustness of sediment transport models) and practical (e.g. computational costs) limitations. In particular, a lack of knowledge of sediment transport processes and how they relate to hydrodynamics makes the application of short-term models to long-term coastal evolution challenging. Even the state-of-the-art coastal area modelling suites (such as Delft3D and MIKE21) consist of relatively simple physics, relying instead on numerous semi-empirical parameterizations, which are often poorly supported by measured data and/or physical process understanding. In particular, suspended sediment transport in the highly turbulent surf zone is poorly modelled under breaking wave conditions. Six existing suspended sand concentration (SSC) models were critically evaluated ...
Implementing the effects of turbulent kinetic energy (TKE) is essential in producing accurate sus... more Implementing the effects of turbulent kinetic energy (TKE) is essential in producing accurate suspended sediment concentration (SSC) models, especially under breaking wave conditions. SSC is commonly attributed to two different turbulent sources under breaking wave conditions: 1) bed-friction and 2) breaking-induced turbulent vortices. Numerous studies have endeavoured to quantify the effects of TKE and incorporate them into SSC models. To name a few: Mocke & Smith (1992, henceforth MS92), Shibayama & Rattanapitikon (1993, henceforth SR93), Jayaratne & Shibayama (2007, henceforth JS07), and Yoon et al. (2015, henceforth Y15). The present study evaluates these 4 existing SSC models and validates them against recently published datasets from the ‘CROSSTEX’ (Yoon & Cox, 2010), ‘SandT-Pro’ (Ribberink et al., 2014) and ‘SINBAD’ (vdZ et al. 2015) projects. Following critical evaluation, suggestions are made to enhance existing SSC models, and these findings are then incorporated into prod...
By analysing and comparing the results of post-disaster field studies and literature regarding th... more By analysing and comparing the results of post-disaster field studies and literature regarding the mechanisms by which coastal structures failed due to the 2004 Indian Ocean Tsunami and the 2011 Tohoku Tsunami events (the focus being on defence structures where applicable), trends were identified and examined. This paper highlights the most commonly occurring / major failure mechanisms identified in the various locations affected by the two tsunami events. The failure modes found in over twenty locations throughout the Fukushima, Iwate and Miyagi Prefectures of Japan were categorised into seven failure modes: a) leeward toe scour, b) crown armour failure, c) leeward armour failure, d) parapet wall failure, e) overturning, f) seaward toe scour, and g) sliding. Leeward toe scour was found to be the major failure mechanism in seawalls and dikes, and sliding was found to be the major failure mechanism in concrete breakwaters. The failure modes found throughout regions affected by the Indian Ocean Tsunami were categorised into five failure mechanisms: a) scouring of foundations, b) beam /column failure, c) joint failure, d) wall failure, and e) total disintegration. The 'total disintegration' caused by seismic forces, debris collision and hydrodynamic forces was the major failure mode throughout the studied regions. Some of the major tsunami induced forces found to have been among the causal factors of structural failure included hydrostatic and hydrodynamic forces. Flow velocities as high as 13.4 m/s were found in areas of Japan, and flow velocities of up to 10.4 m/s were found in regions affected by the 2004 Indian Ocean Tsunami. Potential strengthening measures were suggested for structures such as seawalls and coastal dikes, which were most vulnerable to scouring at the toe. By producing armoured components to protect the toe of the structures, they would become less susceptible to toe scour failure.
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