Extreme storms are responsible for rapid changes to coastlines worldwide. During the 2013/14 winter, the west coast of Europe experienced a sequence of large, storm-induced wave events, representing the most energetic period of waves in the last 60 years. The southwest coast of England underwent significant geomorphological change during that period, but exhibited a range of spatially variable and complex morphological responses, despite being subjected to the same storm sequence. The 2013/14 storm response along the southwest coast of England was first used as a natural field laboratory to explain the variability in storm response through the introduction and evaluation of a new classification of how sandy and gravel beaches respond to extreme storms. Cluster analysis was conducted using an unique data set of pre- and post-storm airborne Light Detection and Ranging (LiDAR) data from 157 beach sites and the calculation of volumetric beach changes and a novel parameter, the longshore variation index which quantifies the alongshore morphological variability in beach response. The method used can be applied to any sandy and gravel beaches where topographic data with sufficient spatial resolution is available. Four main beach response types were identified that ranged from large and alongshore uniform offshore sediment losses up to 170 m3 m-1 (at exposed, cross-shore dominated sites) to considerable alongshore sediment redistribution but limited net sediment change (at more sheltered sites with oblique waves). The key factors in determining the type of beach response are: exposure to the storm waves, angle of storm wave approach and the degree to which the beach is embayed. These findings provide crucial information for the development of coastal studies at regional scale, especially along coastal areas where abrupt changes in coastline orientation can be observed. A 10-year time series (2007-2017) of supra- and intertidal beach volume from exposed and cross-shore transport-dominated sites was used to examine the extent to which beach behaviour is coherent over a relatively large region (100-km stretch of coast) and predictably coupled to incident wave forcing. Over the study period, 10 beaches, exposed to similar wave/tide conditions, but having different sediment characteristics, beach lengths and degrees of embaymentisation, showed coherent and synchronous variations in sediment volumes, albeit at different magnitudes. This result is crucial for studying coastal changes in remote coastal areas or in areas where only few topographic data are available. The sequence of extreme storms of the 2013/14 winter, which represents the most erosive event over at least a decade along most of the Atlantic coast of Europe, is included in the data set, and three years after this winter, beach recovery is still on-going for some of the 10 beaches. Post-storm beach recovery was shown to be mainly controlled by post-storm winter wave conditions, while summer conditions consistently contributed to modest beach recovery. Skilful hindcasts of regional changes in beach volume were obtained using an equilibrium-type shoreline model, demonstrating that beach changes are coherently linked to changes in the offshore wave climate and are sensitive to the antecedent conditions. Furthermore, a good correlation was found between the beach volume changes and the new climate index WEPA (West Europe Pressure Anomaly), which offers new perspectives for the role and the use of climatic variations proxies to forecast coastline evolution. A process based model, XBeach, was used to model storm response at one macrotidal beach characterized by the largest sediment losses during the 2013/14 sequence of extreme storms. Beach volume changes were modelled over hypothetical scenarios with varying hydrodynamics conditions and beach states to investigate the relative roles of hydrodynamic forcing (i.e., waves and tides), beach antecedent state and beach-dune morphology in beach response to extreme storms. This modelling approach is applicable to any beach system where process based models have been implemented. Beside significant wave height and peak wave period, the beach antecedent state was shown to be the dominant factor in controlling the volumes of sediment erosion and accretion along this cross-shore dominated beach. Modelled volumes of erosion were, on average, up to three times higher along an accreted beach compared to an eroded beach for the same wave conditions. The presence of a dune, being only significantly active during spring tides and storm conditions along this macrotidal beach, was shown to reduce erosion or even cause accretion along the intertidal beach. This work provides a detailed, quantitative insight of the hydrodynamic and morphological processes involved in storm response and beach recovery on a number of spatial and temporal scales. This improved understanding of the potential impact of extreme events will hopefully aid future research efforts and ensure effective management of sedimentary coastlines.

A three dimensional time-dependent coupled ecosystem model is applied to Izmir Bay for the first time. Delft3D modelling suite&rsquo / s FLOW and ECO modules are adapted and tuned for the region. A reference model with a time frame of three years is produced that represents the current physical and biogeochemical status of the bay. Model skill assessment methods are used as a measure of model performance and to address the shortcomings of it. The hydrodynamics model is able to produce physical features in terms of seasonality and spatial distribution within reasonable ranges, whereas the ecosystem model has certain discrepancies which can be reduced with improved quality of model inputs, such as open boundary conditions, and fresh water and nutrient fluxes. The reference model is used as a tool with predictive capacity to assess the ecosystem response of the bay to possible changes it may undergo in the future. Five nutrient enrichment/reduction scenarios are constructed to predict the reactions of the bay to changing external inputs of DIN and PO4. Results suggest that both physical and biogeochemical properties of the bay show strong horizontal gradients between outer and inner regions in which both natural and anthropogenic influences are effective. It is revealed that Outer bays are mostly occupied by waters originating from the oligotrophic Aegean Sea, while eutrophicated inner regions are mainly controlled by local influences such as increased fresh water inputs and excessive wastewater discharges. Results of the nutrient enrichment/reduction scenarios suggest that the N-limited Inner and Middle bays and the P-limited Outer bays, give contrasting reactions to changes in inputs of DIN and PO4 such that the former is more sensitive to DIN input whereas the latter is more sensitive to PO4 input. Due to the existence of these two contrasting environments in the bay, availability of one nutrient is dependent on the availability of the other, therefore treatment of both should be considered in parallel. Among the scenarios tested in this study, the best possible option to reduce eutrophication in Izmir Bay is to prevent the increase of PO4 input and to reduce the DIN input simultaneously. These outcomes are aimed to provide a scientific insight for coastal policy makers and environmental managers on how changes in anthropogenic influences can impact the marine ecosystem of the bay.

Acid Sulphate Soils (ASS) often cause acidic pollution in canal water, which negatively impacts on water quality, biodiversity and the livelihood of farmers and fishermen, especially the landless poor. The problem is particularly acute in the coastal zones, where people already suffer from the consequences of salinity intrusion. Reducing acidic pollution is important for improving agricultural and aqua-cultural production and also the living conditions of people living in coastal zones with ASS. This study aims at developing an analytical tool that can simulate the propagation of acidic pollution and that would allow planers and managers to develop water management options and other resource management measures to reduce acidic pollution in the canal network of a coastal zone. / This study utilizes a systems approach, with a series of field, laboratory studies, in combination with statistical and GIS-based analyses and simulation modelling. Field and laboratory studies were carried out during 2001 - 2006 in Ca Mau peninsula, Mekong Delta, Vietnam, to fill in knowledge gaps on the source and amount of acidic loads from soil to the water surroundings, their interaction with saline water and their propagation in the canal network. Knowledge generated from this study was used in developing and validating a model to simulate the propagation of acidity in the tidal canal network with brackish water. / Measured data showed that the acidic pollution in the canal network varies seasonally. The pH of the canal water was lowest (3 – 4.5) at the beginning of the rainy season and highest (7 – 7.5) at the end of the rainy season and during the dry season. The reduced dredging activities in year 2005 and 2006 may explain why the acidic pollution decreased in 2005 – 2006 compared with 2001 –2004. The most serious acidic pollution occurs when the two following conditions are present simultaneously: (i) The existence of newly dredged canals (and hence the deposition of the excavated spoils on the canal embankment) in areas with ASS (especially with a severe ASS); and (ii) little or a lack of water exchange from tidal flows. Field experiments showed that ASS embankments within 2-3 years after dredging represent a high acidity hazard because they can release into the canal a total acidity, mainly from runoff and seepage water, of up to 2.7 mol H+day-1 per meter length of canal embankment. Functional relationships were established allowing quantification of the daily acid load transferred from fields and canal embankments to the canal network. / A laboratory titration experiment showed that saline water could buffer the effects of acidic pollution in the canal water. A new ACIDITY module was developed and was coupled to an existing hydraulics and salinity model (the Vietnam River Systems And Plains - VRSAP). The model was calibrated with measured data from 2003 and validated with data from 2005. The Model is the first of its kind able to simulate the temporal and spatial dynamics of changes of pH (as an indicator of acidity) at a regional scale, together with salinity and water flow characteristics in a tidal canal network with brackish water. The Model can be used to investigate the effects of different scenarios of water and other resource management options on the extent of acidic pollution in a coastal area. Analysis of simulation runs for various scenarios indicate that opening the two main sluices along the East Sea at high tide in one day every week in May and June for saline water intake, combined with widening the canals that connect these sluices to the West Sea can eliminate the acidity problem in the study area. Large scale dredging of canals of ASS in fresh water zone should be avoided as it can create severe acidic pollution of the canal water.

Co-location of offshore wind turbines at sites being developed for tidal stream arrays has been proposed as a method to increase capacity and potentially reduce the cost of electricity compared to operating either technology independently. This research evaluates the cost of energy based on capital expenditure and energy yield. It is found that, within the space required around a single 3 MW wind turbine, co-location provides a 10-16% cost saving compared to operating the same size tidal-only array without a wind turbine. Furthermore, for the same cost of electricity, a co-located farm could generate 20% more yield than a tidal-only array. These results are based on analysis of a case-study site in the Pentland Firth. Wind energy is assessed using an eddy viscosity wake model in OpenWind, with a 3 MW rated power curve and thrust coefficient from a Vestas V90 turbine. Three years of wind resource data is from the UK Met Office UK Variable (UKV) 1.5 km numerical model and corrected against a 400 m Weather Research and Forecasting (WRF) model run over the site. Tidal stream energy is modelled using a semi-empirical superposition of self-similar plane wakes, with a generic 1 MW rated power curve and thrust based on a full-scale, fixed-pitch turbine. Coincident tidal resource data is from the Forecasting Ocean Assimilation Model (FOAM) at 7.5 km resolution and correlated with a 150 m ADvanced CIRCulation model (ADCIRC). Wave parameters are corrected from ERA-Interim data with six months of wave buoy data. Multiple tidal turbine array layouts are considered, with maximum tidal energy generated for a staggered array with spacing of 20 tidal turbine diameters, Dt , streamwise and 1.5Dt cross-stream. However, cheapest cost of electricity from the tidal-only array, was found for a single row of turbines, due to minimal wake effects. Laboratory experiments were undertaken to validate the superposition wake model for use with large, shared support structures. Two rotors mounted either side of a central tower generate a peak wake velocity deficit 70% greater than predicted by superposition. This was due to high local blockage and a complex near-wake structure, with a corresponding increase in tower drag of 9%. Further experiments evaluated the impact of oblique inflow on turbines yawed at +/-15 degrees. These results validated a theoretical cosine correction for thrust coefficient and characterised the centreline wake drift with downstream distance. Extreme environmental loads for a shared support structure, compared to structures for wind-only and tidal-only, have also been modelled. A non-linear wave model was used to represent a single wave form with 1% occurrence for each hour of time-series data. Overturning moment about the base of a shared support, with one wind and two tidal turbines, was found to be 4.5% larger than for a wind-only turbine in strong current and with turbines in different operational states. Peak loads across the tidal array were found to vary by 2.5% and so little load reduction benefit could be gained by locating a shared support in a more sheltered area of the array.