Coastal Flood Risks Under Extreme Waves: Creating Resilience through Retrofitting - Living With Environmental Change (LWEC) - Coastal and Waterway Eng
Lead Research Organisation:
University of Warwick
Department Name: Sch of Engineering
Abstract
Scientific context of the study: The maintenance of the coastal defence structures imposes huge costs to the coastal communities. For example, the total length of the UK's coastline is almost 12 500km, and in England & Wales 44% of the coastline is defended (6% in Scotland) against natural forces, costing approximately £358m each year to maintain, with total replacement costs in excess of £20 billion. Projections are that spending on coastal defences will need to double by 2080 to maintain the present coastline. As engineers struggle to maintain traditional 'hard' defences, such as rock walls, armour or embankments, 'soft' engineering solutions, including the recreation of foreshores and beaches, are rapidly finding favour. The intention of this PhD study is to investigate the effects of climate change (e.g. the combined effects of sea level rise and the now more where gaps in knowledge are known to exist. For typically natural soft defences, the research will address the effects on run-up, wave impact and wave over-wash through a range studies, such as natural beach shape optimization in front of rock-armoured revetments.
The State of the Nation: Infrastructure 2014 (ICE, 2014) reports that Flood Management infrastructure is infrequently maintained and requires attention. The resilience of these structures to the severe weather events is more important because they protect other infrastructure networks from disasters. Current design guidance (e.g. Levee Handbook, CIRIA C731 & EurOtop) predominantly focuses on simple geometric hard defence configurations. In the absence of detailed numerical or physical models, for complex geometries or softer natural defence configurations, engineers currently have to make rudimentary assumptions from current guidance. This leads to large levels of uncertainly in where, when, and how the damages may occur. This does little for the confidence of local authorities and communities in regard to planning, adapting, and mitigating the effects of disasters.
Methodology, and expected results: A number of different case studies will be selected for analysis, giving due considerations to the time and budget constraints. Achieving a good variety between cases is important; in order to achieve a holistic image of morphological changes in different environments.
Different scenarios will be developed, based on the available projections for sea level rise and storm events. Numerical simulations will be conducted for all the developed scenarios, using available models such as SWAN for wave propagation and XBeach for bed updating.
Comparisons between different cases and scenarios can be used to determine the significance and the sensitivity of each variable, by carrying out a number of simulations.
Laboratory testing will be used for calibration and validation of the developed models, and in this task, University of Warwick plays an important role due to its availability of access for good physical modelling facilities. The uniqueness of the methodology will be achieved by integrating existing methods to provide answers to climate change and sea level rise problems.
Significance: Outcomes of this study are expected to provide insights to substantially fulfil the existing knowledge gap related to the impacts of climate change on the morphological variations around rubble mound structures.
Currently, the projections of possible climate change induced impacts are considered when designing and constructing new rubble mound structures. However, the available projections mainly cover the sea level rise (reliably) and the increased intensities of tropical cyclones/hurricanes/typhoons (doubtfully). The outcomes of this PhD vastly improve design methodologies to resist the probable morphological changes around the revetments and breakwaters, which will lead to the creation of a safer coastal environment for future generations.
The State of the Nation: Infrastructure 2014 (ICE, 2014) reports that Flood Management infrastructure is infrequently maintained and requires attention. The resilience of these structures to the severe weather events is more important because they protect other infrastructure networks from disasters. Current design guidance (e.g. Levee Handbook, CIRIA C731 & EurOtop) predominantly focuses on simple geometric hard defence configurations. In the absence of detailed numerical or physical models, for complex geometries or softer natural defence configurations, engineers currently have to make rudimentary assumptions from current guidance. This leads to large levels of uncertainly in where, when, and how the damages may occur. This does little for the confidence of local authorities and communities in regard to planning, adapting, and mitigating the effects of disasters.
Methodology, and expected results: A number of different case studies will be selected for analysis, giving due considerations to the time and budget constraints. Achieving a good variety between cases is important; in order to achieve a holistic image of morphological changes in different environments.
Different scenarios will be developed, based on the available projections for sea level rise and storm events. Numerical simulations will be conducted for all the developed scenarios, using available models such as SWAN for wave propagation and XBeach for bed updating.
Comparisons between different cases and scenarios can be used to determine the significance and the sensitivity of each variable, by carrying out a number of simulations.
Laboratory testing will be used for calibration and validation of the developed models, and in this task, University of Warwick plays an important role due to its availability of access for good physical modelling facilities. The uniqueness of the methodology will be achieved by integrating existing methods to provide answers to climate change and sea level rise problems.
Significance: Outcomes of this study are expected to provide insights to substantially fulfil the existing knowledge gap related to the impacts of climate change on the morphological variations around rubble mound structures.
Currently, the projections of possible climate change induced impacts are considered when designing and constructing new rubble mound structures. However, the available projections mainly cover the sea level rise (reliably) and the increased intensities of tropical cyclones/hurricanes/typhoons (doubtfully). The outcomes of this PhD vastly improve design methodologies to resist the probable morphological changes around the revetments and breakwaters, which will lead to the creation of a safer coastal environment for future generations.
Organisations
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509796/1 | 01/10/2016 | 30/09/2021 | |||
| 1924369 | Studentship | EP/N509796/1 | 02/11/2017 | 30/07/2021 | Nipuni MERENCHI GALAPPATHTHIGE |
| Description | In addition to this award, the award winner successfully received the "Capital Investment Fund" to upgrade the existing laboratory facility in the School of Engineering, University of Warwick. There was an existing flume in the laboratory, which was not being used for a while, and thanks to the capital investment fund, a wave paddle was added to the flume. The other necessary components were designed by the award winner, in order to create a complete wave modelling facility. This facility is now being used for modelling how dissolved pollutants spread in water, in different waves (coastal) and flow (river) conditions. A new methodology, which can be used for quantifying the mixing properties of a given flow condition, was tested against the existing method. The new methodology seems to perform better than the traditional methodology in combined-wave current flow, however the traditional moment-area method seems better for vegetated/non-vegetated open channel flow. Furthermore, an N-zone model which was initially developed by Chikwendu (1986) was used for numerically quantifying the longitudinal mixing in vegetated/non vegetated open channel flow. The N-zone model has provided reasonable and accurate estimations, which can be used for evaluating the longitudinal mixing: if the flow rate and the dimensions of cross section is known in a narrow open channel, or profile of velocity time series is known for a vegetated open channel. The same methodology is applicable in combined-wave-current flow when the submergence of the vegetation canopy is high. For vegetation canopies with lower submergence, an undertow occurrs, which needs the methodology to be slightly modified. When waves move through a vegetation canopy in a combined wave-current flow, the waves attenuate better when the background current is stronger. When the background current is weak (and the hydrodynamic condition is dominated by waves), the wave attenuation decreases in the presence of a weak background current. This has been identifed before in previous work, and the present study add some insight regarding the second order waves: which means the waves propergating on a shallow shore. For example, the results can be used for evaluating the protection caused by a coral reef in a shore which is subjected to a tidal current and wind waves, or the protection caused by a submerged vegetation canopy in an estuaty where a tidal current and wind waves from the sea, coexist. |
| Exploitation Route | The new methodology for measuring hyporheic exchange, can be used for field measurements, specially in combined wave-current flow when vegetation is not present. I have used this method for evaluating the mixing properties in vegetated rivers/wave environments, and it works acceptably well in laboratory conditions. However before applying the methodology in vegetated canals in the field, some further developments has to be made. Previous researchers mainy used the N-zone model which was developed by Chikwendu (1986) for simple open channel flow. Some researchers use the 2-zone model to evaluate the longitudinal mixing coefficients in vegetated channels, and this study presents the applicability of the N-zone model in complicated wave-flow conditions, using measured velocity data. This will help understanding the physical processes around the mixing layer, and to see the contribution of each vertical location of the flow for longitudinal mixing, rather than using an oversimplified model. After I conclude my PhD, we can even continue this topic as undergraduate projects and masters level research. Even at present, some third year and masters students are conducting projects which are linked to this work, and I am sharing my knowledge with them. A new PhD student who joinined the group is taking this knowledge forward, by using the research facility to model the longitudinal mixing in microplastics in vegetated environments. We have collected a good dataset from microplastics, and currently in the process of publishing them. |
| Sectors | Environment |