E-Thesis 577 views 143 downloads
Computational Modelling of the Coastal Protection Function of Salt Marshes with Flexible Vegetation Cover / THOMAS VEELEN
Swansea University Author: THOMAS VEELEN
DOI (Published version): 10.23889/SUthesis.59834
Abstract
Salt marshes are intertidal coastal wetlands that are typically found in sheltered locations such as estuaries. They exhibit a diverse vegetation cover with flexible grasses and rigid shrubs. This vegetation provides coastal protection by attenuat-ing currents and waves. Unlike traditional hard defen...
| Published: |
Swansea
2020
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| Institution: | Swansea University |
| Degree level: | Doctoral |
| Degree name: | Ph.D |
| Supervisor: | Karunarathna, Harshinie ; Reeve, Dominic E. |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa59834 |
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| Abstract: |
Salt marshes are intertidal coastal wetlands that are typically found in sheltered locations such as estuaries. They exhibit a diverse vegetation cover with flexible grasses and rigid shrubs. This vegetation provides coastal protection by attenuat-ing currents and waves. Unlike traditional hard defences, they offer co-benefits by stabilising shorelines and enhancing natural habitats. However, it has remained unclear how salt marshes with a flexible vegetation cover contribute to coastal protection under storms with surge and wave components.In this thesis, I have developed a new coupled current-wave-vegetation model which includes the effect of vegetation flexibility on wave attenuation. The wave-vegetation model builds on novel laboratory experiments using artificial vegeta-tion in the Swansea University Wave Flume, where wave damping, water velocity fields, and plant motion were measured simultaneously for the first time. A new work factor is introduced to explicitly account for vegetation flexibility in compu-tational models. Furthermore, a momentum sink term parameterisation is found to best resemble current-vegetation interactions. The advanced coupled model is successfully applied to simulate flood risk in the Taf Estuary under six contrast-ing vegetation scenarios.My results highlight how the vegetation cover affects the coastal protection pro-vided by salt marshes. All modelled vegetation species constrain flood currents to the main estuary channel and damp incoming waves. Although flexible grasses are 50% less effective in wave damping than rigid shrubs in the Taf Estuary. The wave conditions, wind conditions and local topography further affect the protec-tion provided. Additionally, rigid species can amplify orbital velocities above the canopy by inducing wave-averaged currents, but flexible species do not.It is recommended that the biomechanical properties of vegetation, including the flexibility, are included when modelling the coastal protection by salt marshes. My new computational modelling framework provides evidence to support the continuing uptake of salt marshes as sustainable coastal defences. |
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| Item Description: |
ORCiD identifier: https://orcid.org/0000-0002-7061-8012 |
| Keywords: |
Salt Marshes, Computational Modelling, Coastal Vegetation, Flood Risk, Laboratory Experiments |
| College: |
Faculty of Science and Engineering |