Sewage overflows (SOs) and Combined Sewer Overflows (CSOs) significantly contribute to the bacterial contamination of coastal waters, which is of especial concern for aquaculture, a growing industry worldwide. Hydrodynamic and water quality models were used to investigate impacts of CSO discharge frequency and duration, river discharge and tides on Escherichia coli levels at shellfish farming sites in the Dart Estuary (UK), being the employed methodology generally applicable. High E. coli contamination occurred during neap tides and high river discharges due to higher retention and lower bacterial decay. Synchronicity of CSO spills affected the duration of the pollution episodes rather than peak concentrations, more influenced by discharges of the neighbouring CSOs. During peak discharges, E. coli concentrations could be 10 times higher than during average flows. CSO spills were more frequent when rainfall was >20 mm. Model outputs combined with rainfall forecasts can indicate microbiological contamination risk in the aquaculture sites.

To assess potential dispersion of pollutants around Honiara, Solomon Islands, and Port Vila, Vanuatu, 3D ocean circulation models were developed using Telemac-3D. A series of scenarios then explore the vulnerability of the system and test potential control measures. Results show that high coastal concentrations are most likely during the wet season, with increased volumes of discharge as well as favourable wind speed and direction. Buoyant plumes flow along the coastline, and high concentrations build up in enclosed bays. Control measures tested focus on consolidating existing outflows at depth off-shore. This results in an overall reduction of surface concentrations along the coastline. However, the reduction is dependent on the depth, off-shore positioning, and volume of outflow. With increased concentrations then found at depth, the subsequent impact on off-shore and benthic ecosystems would also need to be considered.

Hydrodynamics play a critical role in determining the trajectory of an oil spill. Currents, stratification and mesoscale processes all contribute to how a spill behaves. Using an industry‑leading oil spill model, we compare forecasts of oil dispersion when forced with two different hydrodynamic models of the North-West European Shelf (7 km and 1.5 km horizontal resolution). This demonstrates how the trajectory of a deep water (>1000 m) release in the central Faroe-Shetland Channel is influenced by explicitly resolving mesoscale processes. The finer resolution hydrodynamic model dramatically enhances the horizontal dispersion of oil and transports pollutant further afield. This is a consequence of higher mesoscale variability. Stratification influences the depth of subsurface plume trapping and subsequently the far-field transport of oil. These results demonstrate that the choice of hydrodynamic model resolution is crucial when designing particle tracking or tracer release experiments.

This paper presents an approach for preparing a comprehensive national marine ecosystem assessment and its application to the marine and coastal areas of the State of Kuwait. The approach is based on a set of principles to enable diverse data sources, of differing data quality and salience, to be combined into a single coordinated national assessment of marine ecosystem status to support the implementation of ecosystem-based management. The approach enables state assessments for multiple components of the marine ecosystem to be undertaken in a coordinated manner, using differing methods varying from quantitative to qualitative assessments depending on data and indicator availability. The marine ecosystem assessment is structured according to 6 major themes: i) Biodiversity, ii) Commercial Fisheries, iii) Food and Water Quality for Human Health, iv) Environmental Pollution, v) Eutrophication and Harmful Algal Blooms, and vi) Coastal Process and Oceanography. Comprehensive ecosystem assessments are an essential part of implementing the ecosystem approach, however detailed data directly related to clear, specified numerical management targets covering all aspects of a marine ecosystem are rarely available. The development of a State of the Marine Environment Report (SOMER) for Kuwait demonstrates that a coordinated comprehensive ecosystem assessment can be conducted using disparate data, and in relation to partially specified regulatory management objectives. The Kuwait SOMER highlighted the issues of coastal pollution, particularly sewage, for human health and the environment. It shows that the rapid urbanization of Kuwait has led to significant changes in the ecology, with clear impacts on coral reef health, the availability of nesting locations for turtles and habitats for migratory birds. Long-term changes in nutrient input, via waste water and modified freshwater inputs is resulting in demonstrable impacts on a range of marine species and habitats within Kuwait marine waters. It also supports the move towards a regional approach required due to transboundary properties of many of the ecosystem components, drivers and pressures.

A number of sites around the UK are being considered for development of tidal stream energy, one of which is Ramsey Sound off the coast of Pembrokeshire, South Wales. The Sound was used to test the prototype of the Delta Stream by Tidal Energy Ltd. After initial testing, a 10 MW tidal array was proposed at St David's Head. To investigate any possible environmental impacts of the array due to energy extraction, a case study of the Pembrokeshire coast was performed using a high-resolution depth averaged hydrodynamic model, Telemac2D, to investigate changes to hydrodynamics and morphodynamics. Results show that the proposed array of nine tidal energy converters will cause alterations to eddy propagation leading to changes in the velocity field up to 24 km from the tidal array. Changes in morphodynamics are predicted through alterations to the bed shear stress. Changes to the mean and maximum bed shear stress, over a 30-day period, are found to be more localised and extend 12 km from the array. These changes indicate that the proposed tidal array will lead to localised sediment accumulation and will act as a barrier to sediment transport, with potential consequences for the benthic ecology of the region. Crown Copyright (C) 2018 Published by Elsevier Ltd.

A cumulative impact assessment of tidal stream developments in the Irish Sea has been conducted on a high-resolution depth-averaged hydrodynamic model, using Telemac2D. Eight sites were investigated, representing the proposed developments at the time of study. These included: Ramsey Sound, Anglesey, Strangford Loch, Mull of Kintyre, Torr Head, Fair Head, Sound of Islay and West of Islay. Only three projects showed array-array interaction: Fair Head, Torr Head and Mull of Kintyre. A smaller model domain was created for further analysis. Results showed Mull of Kintyre had little impact. Fair Head reduced the energy production at Torr Head by 17%, whereas, Fair Head only reduced by 2%. This was caused by the tidal asymmetry whereby the flood was stronger. When operated concurrently, the maximum power-output at Torr Head is 64.5MW, representing 31% reduction. If Torr Head can still operate commercially in the presence of Fair Head, then the additional environmental impact of Torr Head, such as the change in bed shear stress, is small. Within the Irish Sea, very few of the tidal projects investigated are geographically close to each other. As the industry develops, the risk of interaction to these sites will grow when more intermediary sites are developed.

Phytoplankton form the base of the marine food chain, and knowledge of phytoplankton community structure is fundamental when assessing marine biodiversity. Policy makers and other users require information on marine biodiversity and other aspects of the marine environment for the North Sea, a highly productive European shelf sea. This information must come from a combination of observations and models, but currently the coastal ocean is greatly under-sampled for phytoplankton data, and outputs of phytoplankton community structure from models are therefore not yet frequently validated. This study presents a novel set of in situ observations of phytoplankton community structure for the North Sea using accessory pigment analysis. The observations allow a good understanding of the patterns of surface phytoplankton biomass and community structure in the North Sea for the observed months of August 2010 and 2011. Two physical–biogeochemical ocean models, the biogeochemical components of which are different variants of the widely used European Regional Seas Ecosystem Model (ERSEM), were then validated against these and other observations. Both models were a good match for sea surface temperature observations, and a reasonable match for remotely sensed ocean colour observations. However, the two models displayed very different phytoplankton community structures, with one better matching the in situ observations than the other. Nonetheless, both models shared some similarities with the observations in terms of spatial features and inter-annual variability. An initial comparison of the formulations and parameterizations of the two models suggests that diversity between the parameter settings of model phytoplankton functional types, along with formulations which promote a greater sensitivity to changes in light and nutrients, is key to capturing the observed phytoplankton community structure. These findings will help inform future model development, which should be coupled with detailed validation studies, in order to help facilitate the wider application of marine biogeochemical modelling to user and policy needs.

Current understanding of the behaviour of sea breezes in the offshore environment is limited but rapidly requires improvement due, not least, to the expansion of the offshore wind energy industry. Here we report on contrasting characteristics of three sea-breeze types on five coastlines around the southern North Sea from an 11 year model-simulated climatology. We present and test an identification method which distinguishes sea-breeze types which can, in principle, be adapted for other coastlines around the world. The coherence of the composite results for each type demonstrates that the method is very effective in resolving and distinguishing characteristics and features. Some features, such as jets and calm zones, are shown to influence offshore wind farm development areas, including the sites of the proposed wind farms up to 200 km offshore. A large variability in sea-breeze frequency between neighbouring coastlines of up to a factor of 3 is revealed. Additionally, there is a strong association between sea-breeze type on one coastline and that which may form coincidentally on another nearby. This association can be as high as 86% between, for example, the North Norfolk and East Norfolk coasts. We show, through associations between sea-breeze events on coastlines with contrasting orientations, that each coastline can be important for influencing the wind climate of another. Furthermore, we highlight that each sea-breeze type needs separate consideration in wind power resource assessment and that future larger turbines will be more sensitive to sea-breeze impacts.

Abstract. The behaviour and characteristics of the marine component of sea breeze cells have received little attention relative to their onshore counterparts. Yet there is a growing interest and dependence on the offshore wind climate from, for example, a wind energy perspective. Using idealized model experiments, we investigate the sea breeze circulation at scales which approximate to those of the southern North Sea, a region of major ongoing offshore wind farm development. We also contrast the scales and characteristics of the pure and the little known corkscrew and backdoor sea breeze types, where the type is pre-defined by the orientation of the synoptic scale flow relative to the shoreline. We find, crucially, that pure sea breezes, in contrast to corkscrew and backdoor types, can lead to substantial wind speed reductions offshore and that the addition of a second eastern coastline emphasises this effect through generation of offshore "calm zones". The offshore extent of all sea breeze types is found to be sensitive to both the influence of Coriolis acceleration and to the boundary layer scheme selected. These extents range, for example for a pure sea breeze produced in a 2 m s−1 offshore gradient wind, from 0 km to 21 km between the Mellor-Yamada-Nakanishi-Niino and the Yonsei State University schemes respectively. The corkscrew type restricts the development of a backdoor sea breeze on the opposite coast and is also capable of traversing a 100 km offshore domain even under high along-shore gradient wind speed (>15 m s−1) conditions. Realistic variations in sea surface skin temperature and initializing vertical thermodynamic profile do not significantly alter the resulting circulation, though the strengths of the simulated sea breezes are modulated if the effective land-sea thermal contrast is altered. We highlight how sea breeze impacts on circulation need to be considered in order to improve the accuracy of both assessments of the offshore wind energy climate and forecasts of wind energy output.

Sediment accumulation downstream of hydraulic jumps can occur in many settings but the architectures of such deposits are poorly documented. Here, three flume runs were used to examine the influence of sediment grain size and transport rate on the characteristics of hydraulic‐jump unit bars . In one of these runs six hydraulic‐jump unit bars formed a hydraulic‐jump bar complex . In another, the same sediment was supplied more quickly and only two unit bars formed. In the third run with the same sediment supply rate, but different grain size, only one large unit bar formed. All unit bars developed in a similar way but their size and internal architecture differed; they all resulted from a reduction in sediment transport capacity at the transition from supercritical flow to subcritical flow in the hydraulic jump. After initial onset of sedimentation and unit bar formation, generation of subsequent unit bars may be: (i) related to small changes in sediment flux; and (ii) independent of changes in the hydraulic jump. Continued sedimentation caused changes from oscillating to weak hydraulic jumps and hydraulic‐jump unit bars formed in both circumstances. The flow of water and suspended sediment becomes shallower over the lee of the bar complex. This leads to flow acceleration and a return to supercritical flow conditions. In turn, a chain of such features can form and generate a chute and pool bed morphology. There is an inherent upper size limit to a hydraulic‐jump bar complex due to the changing flow conditions over the growing deposit as the water above it becomes shallower. There is also an amplitude minimum for the development of foresets and subsequent unit bar growth. Hydraulic‐jump unit bars have architectures that should be recognizable in the rock record and because their size is constrained by the flow conditions, their identification should be useful for interpreting palaeoenvironment.

Sea Palling on the East coast of the UK has a series of 9 shore parallel rock breakwaters. The numerical model TELEMAC2D has been used to simulate tidal currents around the system to assess the tidal contribution to sediment budgets and transport pathways. Numerical simulations are particularly useful for identifying the important processes involved in a complex system such as these breakwaters and understanding how the breakwaters might effect the local coastal region. Models are classically evaluated using a number of measurement stations to calibrate and then check it is giving realistic results. It is important to assess both the spatial and temporal performance of a model, but this is difficult with a model having tens of thousands of nodes, based on only a few discrete locations. This paper presents a method using Lagrangian data to assess confidence that can be applied to model performance. Measurements were made by deploying drogues tracked by X-band radar or GPS receivers throughout the breakwater system during calm "no wave" and "no wind" conditions to ensure that only tidal effects were measured. Modelled deployments were made at coincident times and locations for comparison and model performance statistics were calculated. Evidence of a number of features predicted by the model were found, giving confidence to its performance. Radar drogues are cheap to make and data capture onshore reduces the risk of data loss. GPS drogues can be used in a wider spatial area, however their onboard data storage requires drogue retrieval for data download.

Between 1994 and 1997 nine segmented, shore-parallel, rock-mound breakwaters, were constructed at the meso-tidal beach of Sea Palling, on the North Sea coast of the UK, to provide protection for a low lying hinterland vulnerable to storm surge inundation and a 3.5 km section of sea wall that was in danger of collapse due to low beach levels. In this paper we assess the effectiveness of these breakwaters, and of the associated beach recharge events, in stabilising the beaches both within and around the breakwater system, and we examine their impact on the wider littoral drift system. We discuss a 'trapping' mechanism whereby sand entering the system as littoral drift is effectively retained at both ends of the system. At the northern (updrift) end, the trapping of littoral drift sediments, aided by a 1.3 × 106 m3 sediment recharge designed to remedy severe gap erosion, lead to the growth of salients into tidal tombolos (effectively changing the X/h ratio (distance offshore/depth) on Pope and Dean's (1986) morphology-existence diagram). The largest tombolo (Tombolo 5) is at the updrift end, is only inundated during large storm surges, and forms a 260 m wide barrier to littoral drift and the alongshore supply of sediment to breakwater beaches. In response to a large reduction in littoral drift, shorelines in the centre of the system are steadily retreating, with some embayment shorelines being closer to the seawall in 2005 than they were pre-construction. These shorelines have not reached a steady-state and further recharge will be needed unless the littoral drift supply can be restored. The evidence (nearshore morphology, sediment starved beaches, down-drift recharge, shoreline change patterns and a simple sediment budget) indicates that an estimated 80% of littoral drift sediments are directed offshore at Tombolo 5, bypass the breakwaters and downdrift beaches, but may return to shore ~ 2.5 km downdrift. As a direct result of recharge, Sea Palling makes a less-than-ideal case for assessing the applicability of micro-tidal shoreline response equations to breakwaters in tidal settings. The Sea Palling experience also demonstrates that the use of beach recharge in combination with breakwaters in settings of high littoral drift requires very careful consideration as it has the potential to block littoral drift and starve the local beaches — the opposite effect of that intended by both techniques.

This paper presents results from two flume runs of an ongoing series examining flow structure, sediment transport and deposition in hydraulic jumps. It concludes in the presentation of a model for the development of sedimentary architecture, considered characteristic of a hydraulic jump over a non-eroding bed. In Run 1, a hydraulic jump was formed in sediment-free water over the solid plane sloping flume floor. Ultrasonic Doppler velocity profilers recorded the flow structure within the hydraulic jump in fine detail. Run 2 had identical initial flow conditions and a near-steady addition of sand, which formed beds with two distinct characteristics: a laterally extensive, basal, wedge-shaped massive sand bed overlain by cross-laminated sand beds. Each cross-laminated bed recorded the initiation and growth of a single surface feature, here defined as a hydraulic-jump unit bar. A small massive sand mound formed on the flume floor and grew upstream and downstream without migrating to form a unit bar. In the upstream portion of the unit bar, sand finer than the bulk load formed a set of laminae dipping upstream. This set passed downstream through the small volume of massive sand into a foreset, which was initially relatively coarse-grained and became finer-grained downstream. This downstream-fining coincided with cessation of the growth of the upstream-dipping cross-set. At intervals, a new bed feature developed above and upstream of the preceding hydraulic-jump unit bar and grew in the same way, with the foreset climbing the older unit bar. The composite architecture of the superimposed unit bars formed a fanning, climbing coset above the massive wedge, defined as one unit: a hydraulic-jump bar complex.

Shore-parallel breakwater systems built in meso-tidal conditions display a more complicated morphological response than predicted by existing models and their impact on coastlines in the longer term (10-20 years) is unclear. The shore-parallel breakwaters at Sea Palling, UK, built to protect low-lying land from inundation, comprises four surface-piercing and five overtopping breakwaters, spanning a 4.0km length of coast. Earlier studies of the impacts of these breakwaters considered the impacts of waves but neglected the influence of the strong asymmetric tidal currents. TELEMAC was used to simulate tidal currents and elevations around the breakwaters, focussing on sediment transport over the tidal tombolos behind the four, northern-most (updrift) breakwaters; a small amount of wave-stirring (H(s)=0.5m) was also included. The model suggests that the asymmetric tidal currents transport similar to 40,000 m(3) of sand through the system annually, around 20% of the prebreakwater longshore transport rate.Measurements of waves, near-bed currents, suspended sediment concentrations and bedform structures enabled verification of modelled sand transport rates (within 50%). RTK-GPS surveys provided high resolution topography and bathymetry of the beach, tombolo and nearshore seafloor; the rate and direction of tombolo movement from the surveys was also consistent with the modelled transport rates.In addition to the tidally-driven transport, storms drive sand through the breakwater system but erosion of beaches down-drift indicates that the sand supply here is much reduced. Beach and bathymetric surveys over the 10 years since the breakwaters' construction show sand continuing to accumulate at the northern end of the breakwaters but that sand in the longshore transport is also bypassing and accumulating offshore of the breakwaters.

Storm hydrodynamics (waves and currents) and 3-D beach topography were measured in order to assess coastal processes, beach morphodynamics and sediment transport pathways shoreward of a series of breakwaters constructed on a meso-tidal coast (Sea Palling, UK). Suspension of bed sediments, and changes in beach volume and morphology, occur during storms. Whilst wave activity controls sediment mobility and suspended sediment concentration, tidal processes influence erosion patterns and, at the Sea Palling site, the direction of net sediment transport. The coincidence of ebb currents and the emergence of tidal tombolos (due to the progressive-wave nature of the tide) closes the alongshore sediment transport pathway for most of the ebb tidal current duration; this results in a morphologically controlled tidal and sediment transport asymmetry. Thus, high-quality prediction of salient/tombolo size behind breakwaters in a tidal setting is required for an understanding of net sediment-transport patterns. Pre- and post-storm surveys indicate that diabathic sediment exchange occurs during storms, especially at low tide when emergent tombolos prevent littoral drift (offshore transport), and under lower waves when sediment moves onshore, probably as bedload. Tidal tombolos are the most volatile area of the beach, migrating up to 30 m during individual storm events of only a few days.

The interaction between the alongshore, progressive wave tidal currents and the tidal tombolos existing in the lee of the shore parallel breakwaters at Sea Palling, Norfolk, UK, was examined. The TELEMAC2D and ARTEMIS hydrodynamic models were used to simulate tidal flows and waves conditions through the system, determining bed shear stresses and resultant sand transport during a spring-neap-spring cycle. Fieldwork measurements were used to validate the model results and propose values for the relative magnitude of sand transport occurring during calm, low-amplitude wave conditions. These occur as a background to much higher energy, at-shore wave events, the time series analyses of which, have previously been used to evaluate the regional sediment budget.