Coastal defence structures (CDS) are propagating globally. Growing environmental concerns are driving modications to traditional coastal engineering methods through environmentally-enhancing designs which promote biodiversity and socio-economic benefits. Despite a number of tested ecologically-sensitive designs, there is still a gap between research concepts and practical implementations to coastal engineering designs. I investigated design methods for CDS to improve their role as surrogate habitats for coastal assemblages, thus creating more sustainable coastal protection for engineering and maintaining biodiversity. I focused on four key knowledge gaps to identify novel, sustainable and, more importantly, practical methods of designing ecologically sensitive coastal protection: (1) the extent of biological and topographic dissimilarity between natural and artificial shores at dierent scale levels; (2) the use of porous CDS as multifunctional designs for coastal engineering; (3) the use of 3D printing in coastal engineering to design complexity into defence structures; and nally, (4) the impacts of intertidal and subtidal species and their role as natural coastal protection methods. To address the rst knowledge gap, I surveyed seven natural and articial shores on the South coast, UK, comparing the biological communities and topographic complexity on each shore at three dierent scale levels. I found that species characteristic of natural and artificial shores dier, and natural shores tend to be characterised by species such as fucoids and some foliose red algae, while articial shores are largely characterised by invertebrate species. For the second knowledge gap, I surveyed a porous CDS during a groyne reduction process, and compared the coastal assemblages colonising the internal and external habitats of the structure. The results showed signicant dierences in species richness and diversity on internal habitats to external. For the third knowledge gap, I explored the use of 3D printing to design-in complex habitat features to enhance biodiversity on artificial structures. This study showed colonisation of some coastal species, but more importantly identified key limitations when using this novel material in coastal engineering, which are fundamental at this preliminary stage. Finally, to address the last knowledge gap, I investigated the impact of eight intertidal and subtidal mimic species on wave velocity. The results showed signicant reductions in wave velocity due to the presence of all mimics, particularly longer and more flexible species. Additionally, I compared the impact of ve dierent designed tile units on wave velocity. I found significant differences in wave velocity reduction among all tile designs, particularly between units of varying orientations. To conclude my thesis, I summarise the key ndings and evaluate these outcomes in the context of their application to sustainable coastal engineering. I then outline challenges and practical methods for designing sustainable and multifunctional coastal defence schemes.

Coastal flooding is a serious and growing threat, with 200 to 300 million people estimated to live within the coastal floodplain worldwide today. This exposure is not static and it is increasing globally due to rising populations and sea level rise. While there have been scenario-based investigations of future exposure, there is a knowledge gap concerning historic analysis of how exposure to coastal flooding has evolved. Understanding what drives changes in exposure can help us to better predict how exposure may evolve in the future under the combined pressures of climate change induced sea level rise, growing populations and increasing development within coastal floodplains. This thesis developed a quantitative methodology to evaluate the detailed historic evolution of exposure with regards to changing coastal population and other drivers of exposure. This includes formal definitions of exposure with and without defences. The occurrence of damaging coastal and river flooding over a >100 year period in the UK was evaluated which showed that reported flooding has been increasing significantly. Subsequently a framework was developed for quantification of exposure with and with- out defences: new GIS methods were developed to spatially distribute census population data across the indicative floodplain based on residential development patterns observed on historic maps and a rapid inundation model. A time series dataset on changes in defence heights was compiled from historic and contemporary records. A computational FAE (Fraction of Attributable Exposure) technique was used to evaluate the effect of flood drivers on the changing exposure. As a demonstration of the methodology, population exposure to a range of flood events was evaluated at 10 year intervals between 1801 and 2011 for Portsea and Hayling islands in the UK’s Solent region, representing a city with significant flood risk, and a more rural location, respectively. 1801 represents the first UK Census, while sea level data is available at Portsmouth since 1960 and this is extrapolated back to 1801. The results show that exposure has grown significantly at both sites. Annual average people exposure (averaged across a range of recurrence intervals) increased from 176 and 27 to 6,911 and 692 over the study period in Portsea and Hayling, respectively. Most of the exposure in Hayling developed after 1931 when residential areas started to encroach on the coastal floodplain. In Portsea, the exposure grew until 1931 and then decreased until 1981 and is now growing again, following changes in the Portsea population. Population growth and residential development have been much bigger drivers of increased exposure to coastal flooding than sea level rise in the region studied, accounting for 71% and 85.5% of the growth in exposure in Portsea and Hayling, respectively, with sea level rise explaining the balance. The methods presented are generic and could be readily extended to a national level analysis. It could also be repeated elsewhere in the world where the necessary data on population and flood characteristics (land elevation, flood levels, sea level change) are available. By understanding historic changes in exposure, an improved understanding of changes in flood risk can be developed, including a reality check on scenarios to inform future flood risk management.

No description available.

Engineered coastal defence structures are proliferating around coastlines globally to protect expanding urban developments from predicted sea level rise and extreme weather events. In response to evolving marine planning policies, it is becoming increasingly necessary to incorporate ecologically-sensitive design into coastal developments, not only to minimise their environmental impacts, but also to maximise potential ecological and socio-economic secondary benefits. I investigated coastal defence structures as surrogate habitats for rocky shore biodiversity, and the potential for the design of structures to be manipulated to achieve more beneficial outcomes. I focused on three major knowledge gaps that must be addressed in order to effectively incorporate ecologically-sensitive design into coastal defences: (i) the capacity to predict ecological responses to different engineering designs for coastal defence structures; (ii) the potential for ecological engineering interventions to enhance biodiversity on structures; and (iii) stakeholder perceptions regarding the desirability of potential secondary benefits that can be built-in to developments. To address the first knowledge gap, I surveyed 125 intertidal coastal defence structures around the coast of Wales, UK, and modelled the relationship between a number of physico-environmental parameters and the biological communities colonising each structure. Using these data I developed a predictive tool and demonstrated that, given the nature of the shoreline on which a new coastal defence was required (i.e. the surrounding sediments and level of exposure to prevailing wind and waves), it would be possible to predict (with up to 62% confidence) the characteristic community that could be expected to colonise a structure, based on its broad shape, position in the intertidal zone, and abundance of microhabitats. To address the second knowledge gap, I explored the potential for a novel ecological engineering intervention (drill-cored artificial rock pools) to enhance biodiversity on an intertidal riprap breakwater. Over a 30- month period, I found that the artificial pools performed an important ecological function on the structure. They were utilised by numerous species that were not otherwise recorded on surrounding emergent rock surfaces, including taxa that have frequently been reported to be absent or scarce on coastal defences previously (e.g. mobile fauna, lower-shore taxa and proportionally-rarer taxa). Furthermore, the artificial pools were just as productive as natural rock pools and supported a comparable number of species. The composition of communities in artificial and natural pools, however, was different, largely on account of differences in sessile assemblages (i.e. algae and encrusting fauna). The intervention, nevertheless, was an effective and affordable means of ecological enhancement, and has received considerable interest from industry and practitioners. To address the third knowledge gap, I investigated stakeholder attitudes regarding desirability of different potential secondary benefits that may be built-in to coastal developments. Although this study revealed complex and nuanced perceptions across sectors, there was unanimous support for implementing multi-functional coastal defence structures in place of traditional single-purpose ones, and in general the most desirable secondary benefits were ecological ones (prioritised over social, economic and technical benefits). In this thesis I evaluate these outcomes in the context of their application to marine planning and conservation management. I finally conclude by outlining the steps that are necessary to achieve wide-scale and effective implementation of ecologically sensitive and multi-functional design for artificial coastal defence structures that are becoming ubiquitous features of urban coastlines globally.

Les travaux présentés dans cette thèse concernent l’investigation d’une chaîne de conversion d’énergie tolérante aux défauts pour des applications hydroliennes. Cette chaîne est constituée d’une génératrice synchrone pentaphasée à aimants permanents déposés en surface associée à un redresseur MLI. Trois volets complémentaires sont traités : la modélisation, l’optimisation technicoéconomique et la commande plus particulièrement en mode dégradé. Concernant la modélisation, trois approches sont élaborées : la modélisation dynamique en vue de l’analyse de l’effet des profils de la fem sur la qualité du couple, la modélisation analytique de chaque élément de la chaîne de conversion d’énergie en vue du dimensionnement et de l’estimation du coût et de l’énergie extraite, et la modélisation en vue de l’élaboration de la stratégie de commande. Une méthodologie d’optimisation multi-objective du coût d’investissement et de l’énergie extraite pour une durée d’exploitation de 20 ans en tenant compte des probabilités d’apparition de la vitesse des courants marins est réalisée. Cette optimisation intègre les contraintes électriques, thermiques … et la stratégie de commande en mode de défluxage. Concernant la commande, des approches innovantes de commande minimisant les ondulations de couple en mode dégradé liées à l’ouverture d’une ou de deux phases sont développées et comparées. Elles consistent à systématiser la génération de la matrice de changement de base pour avoir des courants sinusoïdaux tout en ayant le déphasage adéquat avec les fems des phases saines. / The works presented in this thesis concern the investigation of a fault-tolerant energy conversion system for renewable marine energy applications. The studied conversion chain is based on a five-phase for surface mounted permanent magnet synchronous generator associated with a PWM rectifier. Three complementary aspects are treated: modeling, technico-economic optimization and control especially in fault mode. Regarding to the modeling, three approaches are developed: a dynamic modeling of the generator in order to analyze the effect of the fems profiles on the torque quality, an analytical modeling of each element of the energy conversion chain for the designing and the estimation of both cost and the extracted energy, and a modeling for the control strategy. A methodology of multi-objective optimization of the investment and energy extracted for an operating period of 20 years by taking into account the probabilities of occurrence of the tidal speed is developed. This optimization integrates the electrical and thermal constraints ... and the flux weakening control strategy. For the control in fault mode, innovative control approaches that minimize the torque ripples related to the opening of one or two phases are developed and compared. They consist in systematizing the generation of the matrix transforms in order to have sinusoidal currents and ensure a proper phase shift with the fems of the healthy phases.

Since the aborted dumping of the Brent Spar in the North East Atlantic in 1995 and subsequent legislation requiring both total removal of platforms and banning of disposal at sea by OSPAR in 1998, operators of offshore platforms have been left with substantially increased decommissioning liabilities. The desire to reduce these liabilities has required the offshore industry to develop new, more cost effective technology for platform removal. The author's sponsoring company, Reverse Engineering Limited (REL), has been involved with the development and engineering of a new technology, the Versatruss System. This system has been used for lifts up to 1,350 short-tons in the Gulf of Mexico and can potentially remove large topsides in one piece, thus allowing the possibility of their reuse. As such, this system provides an ideal opportunity for competitive technology development in the North Sea. This thesis therefore focuses on the development of the Versatruss System for use in decommissioning projects in the North Sea environment. Both a conceptual design methodology and a high level operating procedure for North Sea application are presented. Outline frameworks for the planning, management and execution of the onshore deconstruction and disposal phase of platform decommissioning projects have also been developed by the author. In order to provide a balanced assessment of this technology, procedures for comparing the Health, Safety and Environmental (HSE) impacts of the Versatruss System with established removal and disposal techniques, along with worked examples, are also presented. Various economic models covering all phases of the decommissioning operation have been developed by the author over the period of the project. These models include for the decommissioning, removal and disposal of individual or groups of platforms by both established and new technologies. These models are presented within. A preliminary marketing analysis and recommendations for the development of a formal marketing strategy for Versatruss have also been developed. This work has shown that Versatruss can offer a potential alternative to traditional platform removal techniques. Recommendations for further development are not only confined to design and engineering, but also to the organisation for the commercial exploitation of the Versatruss technology.

Two sets of experiments have been undertaken in compound channels with prismatic and nonprismatic floodplains with different floodplain widths and convergence angles in order to investigate flow behaviour in two-stage channels. Measurements were made of water surface profile, depth-averaged velocity, boundary shear stress distributions and velocity distributions and the results are presented in graphical and tabulated form. Empirical equations have been derived from each type of compound channel, allowing predictions to be made concerning the resistance parameters, n and f, the discharge, Q, the proportion of total flow in sub-areas, %Qj, the evolution of flow in the main channel and on the floodplain along the converging part of the flume, the boundary shear forces, SFj, and the apparent shear forces at a vertical and horizontal interface between the main channel and the floodplain, for a given stage, H. The percentage of flow in the main channel and on the floodplain, as well as the percentage of the boundary shear forces carried by each element in different sections of the compound channel with non-prismatic floodplains, were then compared with the prismatic floodplain cases with the same geometry. The results of these two sets of experiments indicate that they follow the same pattern, although there are some differences due to the effects of backwater and convergence in the flume. The apparent shear forces on a vertical interface, ASFv, are however remarkably different. Based on momentum balance, an analytical approach was developed to estimate the water surface profile in non-prismatic compound channels with different convergence angles, 9. The calculated water surface profiles compared well with the measured ones. It is shown that the Shiono and Knight Method (SKM) predicted lateral distributions of the depth-averaged velocity and boundary shear stress well, especially for prismatic compound channels with wide floodplains. Furthermore, there is a good agreement between the measured and predicted distributions in non-prismatic compound channels, provided the energy slope, Se,is used instead of the bed slope, So. The experimental results were then also used to calibrate the two parameter, ",t, and ",g, in the Exchange Discharge Model (EDM). This revealed that the calibration of the turbulent exchange parameter, wt strongly depends on the Manning's roughness coefficient. In term of compound channels with non-prismatic floodplains it is also shown that the EDM always overestimates the flow discharge for a specific stage.

No description available.

Water distribution systems are often susceptible to failure events, mainly due to component malfunctions, increase in demand and pollution events. However, levels of service to the consumers cannot be compromised. Therefore, to understand the behaviour of distribution systems, performance assessment is important. In this thesis, problem of failure events in water distributions system is discussed and the causes of failure are described. Component failures are selected to simulate the extreme situations in the distribution systems. Random nature of the component failures are simulated by way of employing a Monte Carlo technique based on the failure probabilities of the components. The methodology was illustrated with an example application. Appropriateness of existing network analysis methods to simulate failure events is analysed and their shortcomings identified. To demonstrate the impact of component failures, they are simulated with the hydraulic network analysis model. The traditional demand driven network analysis approach is not sensitive to pressure variations in the system. Therefore, simulating failures with demand driven analysis methods produces inaccurate flows at the nodes. The pressure dependent demand analysis on the other hand, is capable of accommodating the flow redistributions in the water distribution network, caused by failure events. The pressure dependent functions used in the analysis are meant to predict the flows that are consumed by the secondary networks (tree network supplied from primary node). However, representing the secondary network behaviour by using only a few coefficients (as in the PDD functions) do not always results in correct predictions. An alternative method that is based on micro level models (secondary networks) is proposed. Micro level models try to simulate the exact network conditions, taking into account of the consumers piping arrangements. Applying micro level models to a large real network will be a tedious process, as the size of the network will increase by many folds. To avoid the difficulties in the micro level modeling, a method based on artificial neural networks (ANN) is introduced. The ANNs mimic the behaviour of secondary networks in the micro level model. Therefore, instead of physically attaching the secondary networks, ANNs are incorporated with the analysis. The ANN based network analysis model predicts the pressure dependent demand outflows at the nodes. The behaviour of water distribution system is evaluated using performance measures. Existing performance indicators are reviewed and their shortcomings identified. New measures are proposed that give better insights into the behaviour of the system and also the failure experience of the consumers. The improved performance assessment method is applied to a case study network and results were explained.

Variations of the flow characteristicsh ave been investigatedf or the flow propagationd ue to a dam-plate removal. Experiments were carried out for various water depth ratios (Hj/H,, 0,0.1,0.45,0.7) in a flume with / without an obstacle downstream of the damsite. Measurementso f flow characteristicsw ere made in the laboratory using a Particle ImageV elocimetry (PIV) system.T o assessth e accuracyo f the PIV measuremenst ystem, Water Level Meter (WLM) measurements have been taken. Comparison of PIV and WLM measureds urfacee levationsa re presentedT. he image analysiss ystemv isualisedt he jet and mushroom formations as complex flow in the downstream section for the low depth ratios. The video image also illustrated the oscillation flow in the downstream channel for the high depth ratios. One-dimensional analytical and numerical calculations have been presented to simulate the experimental results. The numerical models use a semi-implicit Lagrangian finite difference scheme and a WAF Riemann problem based method, the governing equations being the Saint-Venant equations for an invisid and incompressible free surface flow. The models have the advantage that water motions can be simulated, and give particularly good results for the subcritical flow. In general, the models produced good agreement with experimental results.