The Swansea Bay Tidal Lagoon (SBTL) will be the world’s first purpose-built tidal energy lagoon. The 320MW pathfinder project aims to provide a scalable blueprint for tidal lagoons, opening up the option of a fleet of larger UK tidal lagoons to generate renewable electricity.
The project is situated at Swansea Port, approximately 2.2km southeast of Swansea city centre. The Lagoon will enclose part of Swansea Bay, from the eastern side of the River Tawe (western landfall) to the eastern edge of the Swansea University Bay Campus. The seawalls impounding the Lagoon will extend approximately 1.5km directly offshore from SUBC, adjacent to Crymlyn Burrows Site of Special Scientific Interest (SSSI). The seawalls will then extend in a southwest direction along the western boundary of the training wall of the River Neath Channel. A turbine and sluice gate housing structure will be located in the south west of the Lagoon, at an oblique angle to the dredged channel of the River Tawe. The seawall will then extend north towards Swansea Port, close to the mouth of the River Tawe, parallel but offset by 100m from the dredged channel for the River Tawe and Port of Swansea. In total, this will form an approximately 9.5km-long, U-shaped, seawall which will impound approximately 11.5km2 of the seabed, foreshore and intertidal area of Swansea Bay.
The hydro (water) turbines located within the turbine and sluice gate housing will be bi-directional, meaning they are able to generate power with flows of water in both directions (i.e. on both incoming and outgoing tides). There will be up to 16 x 20 MW turbines, each one around 7m in diameter, and all located permanently underwater. There will also be eight sluice gates; these are large gates which will be underwater and able to let seawater in and out of the Lagoon, and so controlling the water passing through the turbines, as required.
To generate electricity, as the sea starts to rise (flood tide) from low tide level, water is prevented from entering the Lagoon for an average of 2.5 hours, which creates a difference in water levels known as ‘head’. Once sufficient head has been reached, the water is allowed to flow into the Lagoon through the turbines, turning the runner (like a propeller) and generating electricity. This process is repeated on the ebb tide, where the water is prevented from leaving the Lagoon until there is sufficient head to start the process again.
It is intended that the project will commence no later than the end of June 2020, by a land-based focused commencement of the access road running in a north-easterly direction. Thereafter, the SBTL’s main works principally comprising construction of the seawall, turbine structure, sluice structure and mechanical and electrical installations will commence in due course.
The Project is situated at Swansea Port, approximately 2.2km southeast of Swansea city centre. The Lagoon will enclose part of Swansea Bay, from the eastern side of the River Tawe (western landfall) to the eastern edge of the new Swansea University Bay Campus (SUBC - previously known as the Science and Innovation Campus, and currently under construction) (eastern landfall).
Swansea Bay Tidal Lagoon is planned to be an offshore generating station with more than 100MW of installed capacity and, as such, is considered a ‘nationally significant infrastructure project’ (NSIP) under the Planning Act 2008.
NSIPs are consented under a different system to that managed by local authorities, being managed instead by the UK’s Planning Inspectorate and consented by the relevant Secretary of State. The Project lies in Welsh waters, meaning a Marine Licence (for dredging and construction) is also required under the Marine & Coastal Access Act 2009. Marine Licence applications are determined by the Marine Licensing Team of Natural Resources Wales (NRW) on behalf of the Welsh Government.
The Project cannot go ahead without both consents. Planning consent was granted by the Secretary of State for Energy and Climate Change in June 2015.
The status of licences or leases required to enable completion of the main works is as follows (marine works will not commence until all necessary leases, consents and licences are in place):
- Decommissioning programme approval (BEIS) – public consultation of this document underway;
- Marine Lease/Seabed rights (The Crown Estate) – to be discussed and agreed in advance of main works (marine) construction commencement;
- Marine Licence (NRW) – on-going. To be approved in advance of main works (marine) construction commencement;
- Third party land options (multiple land owners) – on-going;
- Third party easements for cable route (multiple land owners) – on-going;
- Pre-works commencement requirements as detailed in the Development Consent Order (DCO) (for submission to Local Planning Authorities) – on-going. All DCO requirements to be discharged in advance of main works (marine) construction commencement.
- Electrical connection agreement (National Grid) – on-going.
The company received planning consent on June 09, 2015, but in order for marine works to start the project also needs a marine licence from the Welsh government’s body in charge of sustainable management of its natural resources, Natural Resources Wales (NRW). In December 2016 it became apparent that NRW could deny a marine licence on the basis that the project would result in ‘major adverse effects’ as it was predicted, by NRW, to potentially kill 21% of salmon and 25% of sea trout every year.
TLSB responded saying they had demonstrated minimal impacts on fish which was verified when their planning permission was awarded on the data that was provided in the EIA. TLSB highlighted that their work has been peer reviewed and agreed by a host of world leading fish experts.
In January 2017, a report by former energy minister Charles Hendry ordered by the UK government recommended that tidal lagoons could play “a cost-effective role in the UK’s energy mix”, adding that there was “considerable value in a small pathfinder project”. If constructed, the project would provide enough power for 155,000 homes, or over 90% of homes in the Swansea Bay area.
In January 2018 the First Minister of the Welsh Government announced financial support for the project almost a year after the Hendry review recommended it be backed.
On the 25th of June 2018 the Department for Business, Energy & Industrial Strategy (BEIS) rejected the plan for the tidal lagoon in Swansea Bay, delivering a report to Parliament on the status of tidal lagoons with a cost-benefit analysis that indicated the project was too expensive compared with nuclear and offshore wind power. A follow-up audit of BEIS’ statement by TLSB claimed that figures included in the statement were inaccurate by orders of magnitude.
An independent report published in August 2018 by financial experts Holistic Capital provided a set of recommendations for alternative delivery and financing models, stating that the tidal lagoon was a fundamentally strong proposition and an exceptional project that could provide clean power for generations to come.
In December 2018 eleven companies expressed their interest in the project. Some have indicated they would deliver the entire project, which has an estimated £1.3 billion price tag, but with a different development and deal to the previous proposal. Other companies have said they want to be involved in delivering part of the project.
In December 2019, TLSB launched a fundraising bid to raise £1.2m to support the commencement of land-based material works before the development consent order (DCO) expired on 30 June 2020.
Work on the site was initiated on 29 June 2020, but on 30 June the DCO lapsed and therefore, according to Swansea Council, no part of the previously authorised development could now proceed in the absence of further order or other consent. It is unclear what TBSL’s plans are for the project. As of June 2021, the project had not materialised because of a lack of UK Government support needed to guarantee the project’s viability. The tidal lagoon concept has since been revived in Wales, and between March and May 2020, the Welsh Government launched a marketing exercise to ascertain what level of support existed for such a project. In early June 2021 it was announced 55 companies had shown interest in helping to develop a tidal lagoon off the Welsh coastline, with written submissions received from 27 organisations.
In October 2021, the tidal lagoon project in Swansea finally received funding, as part of a wider project proposed by an international consortium led by DST Innovations. The £1.7bn Blue Eden project at Swansea’s waterfront in Wales will feature the 9.5 km long tidal lagoon structure. Depending on planning consent, work on the Blue Eden site is likely to begin by early 2023.
Key Environmental Issues
These include potential impacts on fish and changes to coastal processes and sediment transport in the area.
Additional data will be collected to support the validation of each of the impact assessments in the Environmental Statement. The developer plans to undertake pre-construction, construction and operational monitoring. The information provided below focuses on construction and operational monitoring. Proposed construction monitoring is included where deemed appropriate.
TLSB noted in the project’s draft decommissioning programme that the resulting Environmental Statement included assessment of the environmental impacts related to the decommissioning phase and was submitted as part of the consent application. When the final decommissioning measures are known, TLSB will review the original EIA to assess the potential impacts that may arise and are not covered in the initial EIA process and subsequent reviews. At this point, a decision will be made as to whether a more detailed assessment is required.
Environmental Webpage: http://www.tidallagoonpower.com/environment/
Papers, Reports, Research Studies
An Environmental Impact Assessment was carried out for the proposals in 2014. The Environmental Statement chapters can be downloaded from here
An Adaptive Environmental Monitoring Programme can be found here.
In April 2020 TLSB issued a draft decommissioning programme for public consultation, closing in the 30 April 2020. The consultation document can be accessed here.
Baseline Assessment: Swansea Tidal Lagoon (SBTL)
|Receptor||Study Description||Design and Methods||Results||Status|
|Marine Mammals||Otter survey||A survey targeting specific areas within the wider study area which were considered to provide potential cover for Otters at locations was undertaken. The survey concentrated on areas considered to be more likely to be subject to disturbance during construction and operation of the Project.||A survey targeted along the seawall and at the south-western end of Swansea Docks (Queens Dock) found evidence of Otters at two locations. Spraints were found under the landward end of a jetty and nearby beside the dock edge (within 20m) at the eastern end of Queens Dock. A sheltered area beneath the jetty was identified as having the potential to provide a laying-up location (a partially enclosed feature used by Otters for temporary refuge). However, September 2013 trail camera footage captured images of a dog investigating this potential laying-up location. If this is a regular occurrence, it is unlikely that the location would be used by Otters as a refuge. |
Tar spots (small drops of feces lacking solids such as fish bones) were also found at the firing-position of a Second World War pill box located within the seawall. The tar spots smelt strongly of Otter and suggest pill boxes provide access points through the seawall allowing movement from the docks to the coast.
|Fish||Intertidal and subtidal surveys to provide an up-to-date characterisation of fish resources in the study area.||Intertidal - Four surveys carried out over one year. Beach seine net (43m long by 4 m deep, with 6.5mm knotless mesh) set from a small rigid vessel and a riley push-net (1.5 m wide by 30 cm deep with 1 mm fry mesh) used from the shore. |
Subtidal - Four surveys carried out over one year. The subtidal surveys were carried out from a 12.1 m mono-hull trawler using both otter and beam trawls.
|A total of 55 species were captured during the site-specific intertidal and subtidal surveys. The fish population has an abundant pelagic fish community with relatively high numbers of sprat (42.6%), herring (12.2%) and sand smelt Atherina presbyter (4%); these account annually for approximately 58 % of fish in Swansea Bay. The most abundant demersal species (whiting, bass Dicentrarchus labrax, pouting, lesser spotted dogfish Scyliorhinus canicula and poor cod) make up 14% of the fish population; whilst benthic species (Goby species, plaice, grey gurnard, common sole, thornback ray Raja clavata, lesser sandeel Ammodytes tobianus, dab, sand goby Pomatoschistus minutus, hooknose Agonus cataphractus, solenette Buglossidium luteum, turbot and flounder) make up 24% of the annual distribution of fish. The remaining 3% of the annual fish population in Swansea Bay is composed of 37 species, each with an abundance of less than 0.1%. The numbers of these fishes are inflated by the appearance of juveniles during the summer months. |
The Swansea Bay fish community showed seasonal fluctuations relating to movements of species between feeding, spawning and nursery areas. During summer a variety of species moved into shallow inshore (intertidal) areas to feed, whilst during winter fish migrated further offshore into deeper (subtidal) waters. These changes are as a direct consequence of temperature, ontogenic development and prey availability.
The shellfish community within Swansea Bay includes molluscs, crustaceans, echinoderms and cephalopods. A total of 38 species were captured during the 4 Quarterly site-specific intertidal and subtidal surveys. The ten most frequently caught species across the 4 quarterly surveys were: i. Brittle Star Ophiura ophiura found in the winter, spring and autumn surveys; ii. White furrow shell Abra alba found in the autumn survey with high abundance; iii. Moon Jellyfish Aurelia aurita found in the summer survey with high abundance; iv. Common starfish Asterias rubens found across all seasonal surveys; v. Shrimp Crangon spp. found across all seasonal surveys; vi. Prawn Palaemon spp. found across all seasonal surveys; vii. Common cockle Cerastoderma edule found in the autumn survey with high abundance; viii. Sea mouse Aphrodita aculeata found across all seasonal surveys; ix. Common hermit crab Pagurus bernhardus found across all seasonal surveys; x. Dog whelk Nucella lapillus found in the spring, summer and autumn surveys.
|Birds||The objective of the surveys was to obtain site-specific data on the numbers of, and primary areas used by, birds within the Blackpill SSSI and River Neath WeBS count areas, with particular reference to the eastern area of the Bay||Surveys were completed on a monthly basis over the winter period 2011/12 (October-March) and 2012/13 (September – March). These winter surveys were supplemented by counts in the east of the survey area (EE013-EE023; River Tawe - River Neath) over the summer period (April-August 2013)||During the field surveys and through literature review, various areas have been identified within Swansea Bay as being used by Divers and Grebes. These areas extend from Port Talbot Dock in the southeast, off Aberafan beach through to the waters off the Port of Swansea and heading out to Mumbles. |
A large number of bird species were identified during the bird surveys, species are split into Waders & waterfowl, Gulls and Divers and Grebe. A list of these species can be found in table 11.9 of the Coastal Birds chapter of the ES.
|Birds||Breeding/overwintering bird survey||The breeding bird survey followed a methodology utilising a combination of defined transects routes supplemented by mapping of birds seen or heard using Common Bird Census (CBC) codes of the British Trust for Ornithology (BTO). Three survey visits during the bird breeding season (March-July/August) were undertaken.||Species recorded during breeding bird surveys in April, May and June 2013 have included Carrion Crow (Corvus corone), Jackdaw (Corvus monedula), Cormorant (Phalacrocorax carbo), Mallard (Anas platyrhynchos), Gadwall (Anas strepera), Buzzard (Buteo buteo), Ringed Plover, Bullfinch (Pyrrhula pyrrhula), Blackbird (Turdus merula), Song Thrush (Turdus philomelos), Mistle Thrush (Turdus viscivorus), Wood Pigeon (Columba palumbus), Swallow (Hirundo rustica) and Common Sandpiper (Actitis hypoleucos). |
Of these, Skylark, Linnet, Bullfinch, Dunnock, Lapwing, Ringed Plover, Song Thrush, Yellow Wagtail, Herring Gull and Black-headed Gull are section 42 NERC 2006 species. The records for Bullfinch, Yellow Wagtail and Black-headed Gull were flyover records.
|Bats||Bat survey||A single surveyor (accompanied for reasons of health and safety) carried out each survey armed with a Pettersson D240x time expansion detector and Edirol R-09HR digital MP3 sound recorder. In addition, an automated bat detector (Anabat SD1 frequency division detector) was deployed for a minimum of four consecutive nights to coincide with each visit. Survey visits were undertaken on 16 May 2013, 5 July 2013 and 3 September 2013||The first of three transect surveys targeting habitat at the western end of Queens Dock and including habitat beside the seawall was undertaken on 16 May 2013. The survey coincided with high tide. Bat activity on the landward side of the seawall was found to be very limited during the visit. However foraging activity of both Common Pipistrelle and Soprano Pipistrelle was recorded alongside exposed rock armouring on the coastal side of the seawall. The first bats recorded during the survey appeared almost one hour after sunset suggesting roosts are distant from the study area. |
Two further surveys on 5 July and 3 September 2013 identified similar activity by both Common and Soprano Pipistrelle bats, although a brief pass by a Noctule was also recorded by a static detector on 6 August 2013.
The September static detector survey identified further passes by Noctule, a species of Myotis and Nathusius Pipistrelle (Pipistrellus nathusii). Nathusius Pipistrelle passes were recorded on the nights of 3, 4 and 5 September 2013. Nathusius Pipistrelle are rarely recorded bats, with only 850 existing records for the UK and Ireland. It is a species that feeds on aquatic flies and is often associated with lakes and rivers (Russ, 2013).
No structures suitable for supporting roosting / hibernating bats that would be affected by the Project, including the electrical grid connection works, were recorded during the field surveys.
|Invertebrates||Onshore invertebrate survey||The invertebrate survey focused on investigating habitat associated with the estate of the Port of Swansea ("Docks Estate") largely comprising brown-field land supporting areas of hard-standing as well as grassland habitat and small areas of scrub. Two-intensive moth–trapping visits were undertaken in July and early August 2013. Incidental invertebrate records were also taken during botany and reptile survey visits.||Incidental records of invertebrates made during site visits to Swansea Docks, particularly during warm weather of June to August 2013 included the Small Heath, Large White, Green-veined White, Small Blue (Cupido minimus), Meadow Brown (Maniola jurtina) and Common Blue (Polyommatus icarus) butterflies, Common Field Grasshopper (Chorthippus brunneus) as well as a Click beetle (Agrypnus murinus) (a species associated with coastal grasslands). |
The invertebrate surveys recorded a relatively diverse fauna of common or locally common species reflecting the mosaic of semi-natural habitats present. A review of the habitat preferences and food plants associated with the section 42 NERC 2006 and localised species found during the 2013 surveys suggested a correlation with coastal grasslands communities present within the docks.
|Reptiles||Onshore reptile survey||Survey effort for reptiles focused on grassland habitat to the south and west of Queens Dock where an absence of records existed. A series of artificial refugia (or ‘tins’) were deployed at potentially suitable reptile basking sites. The tins consisted of 50 x 50cm squares of heavy-duty roofing felt.||Open water with the potential to support breeding amphibians is limited within the study area for the Project. Irregularly inundated ditches and hollows at the northern edges of Crymlyn Burrows support wide ranging species, particularly Common Frog and Palmate Newt (URS, 2010b). However, the presence of Great Crested Newts is considered unlikely due to absence of suitable breeding ponds. |
The reptile surveys confirmed the presence of Common Lizard within coastal grassland habitat alongside the seawall to the south of Queens Dock. Common Lizards were discovered in low numbers on eight of the eleven visits. On each of these occasions one to two individuals were recorded with the exception of a visit in late May 2013 when six individuals were recorded (four adults / two juveniles). Using the criteria of Froglife (1999) the discovery of 5-20 individuals of Common Lizard during any one survey visit is considered to represent a ‘Good’ population.
|Physical Environment||Geophysical and benthic characterisation survey including sampling and particle size analysis||Survey area covers the proposed footprint of the lagoon||Evidence from the geophysical survey and the PSA analysis of surface samples identify that the seabed within the proposed footprint of the Lagoon is divisible into two distinct zones (east and west), separated by an irregular central strip, which represents an outcrop of hard sediments (interpreted as boulder clay). In the western part of the Lagoon footprint, the seabed sediments predominantly comprise sandy gravel and gravelly sand, often with a thin sand veneer. The geophysical survey further indicates that the gravel is particularly coarse at the shoreline to the east of the Swansea Dock entrance breakwaters. A preliminary geotechnical investigation for the Swansea Tidal Lagoon development (Atkins, 2013), which included a number of exploratory boreholes, vibrocores and cone penetration tests, indicates that the seabed sediments found across the western side of the lagoon footprint range in depth from around 0.25 to 0.8 m. Beneath these sediments are numerous layers of (medium) sandy sediments, with varying proportions of silt/ clay and gravel.||Completed|
|Physical Environment||Phase 1 habitat survey - Intertidal and subtidal benthic ecology; Terrestrial ecology ||The intertidal survey was conducted between Mean High Water Springs (MHWS) with the seaward boundary following Mean Low Water Springs (MLWS) (or as near as possible depending on surf and surge conditions). The surveys were undertaken on 14-15 January 2013 and 28-29 May 2013, at low water during spring tides |
Subtidal survey - In order to gather benthic information across the range of different substrates within Swansea Bay, 27 samples were taken from within the footprint of the Lagoon and 22 samples were taken from the area surrounding the Lagoon, providing a total of 49 benthic samples. Three benthic grab samples were collected at each site using a refined compact 0.1m2 Hamon grab
|The survey noted the presence, distribution and condition of Sabellaria reefs adjacent to the Tawe Dock entrance. In addition the survey confirmed the presence and distribution of any nationally important biotopes, protected habitats or rare species both here and across the intertidal area west of the River Tawe round to Mumbles Head. |
The mapping was undertaken on foot. Aerial photography and satellite images were taken into the field to create sketch maps. Habitats in the area were mapped as polygons using the European Nature Information System (EUNIS) habitat classes to level 4 or 5. Biotopes, or other notable features, covering less than 5m2 were recorded using referenced target notes.
Area between River Tawe and River Neath
The upper limit of this rock habitat is dominated by lichens (corresponding to the biotopes LR.FLR.Lic.YG – yellow and grey lichens on supralittoral rock and LR.FLR.Lic.Ver.Ver – Verrucaria maura on very exposed to very sheltered upper littoral fringe rock) with the lower rock dominated by barnacles, limpets and other sea snails with occasional bands of seaweeds (LR.HLR.MusB.Sem.Sem - Semibalanus balanoides, Patella vulgata and Littorina spp. on exposed to moderately exposed or vertical sheltered eulittoral rock).
During the 2013 survey, at the far west of the rock wall close to the breakwater, two seaweed zones of Pelvetia canaliculata (channelled wrack seaweed) and Fucus spiralis (spiral wrack seaweed) were observed below the lichen dominated top shore (Figure 8.7, Volume 2). These correspond to the biotope codes LR.LLR.F.Pel – Pelvetia canaliculata on sheltered littoral fringe rock and LR.LLR.F.Fspi – Fucus spiralis on sheltered upper eulitoral rock, respectively. Zones of Enteromorpha and barnacle and limpet zones occurred below this.
In the far eastern section of the survey area the lower rock is dominated by barnacles, limpets and patches of green algae (LR.HLR.MusB.Sem.Sem and LR.HLR.MusB.Cht.Cht).
a variety of habitats were recorded throughout the lower intertidal with the majority focussed in the western corner of the survey area, including a number of nationally protected habitats and species (e.g. S. alveolata and hydroid rockpools).
In the vicinity of Swansea Bay, the sediments are best described as a mixture of circalittoral mud and sand with the respective composition of each varying spatially. These predictions are broadly consistent with previous descriptions of the Bay which outline the dynamic nature of the area and the high tidal range. This, along with the curved shape of the Bay which results in varied exposure, gives a range of sediments grading from gravely sand, through fine sand to sandy mud and muddy sand in the subtidal area.
|Physical Environment||Phase 1 habitats survey, including botanical survey||An extended phase 1 habitat survey of the terrestrial elements of the Project was begun during site visits between 27 November 2012 and 9 January 2013. The results of the initial survey were updated following repeated visits to the site through the spring and summer of 2013. JNCC 2010 habitat survey techniques were used, with habitats and other features of ecological interest being mapped and described using target notes.||Rocky shore (artificial) |
The southern boundary of Swansea Docks comprises rock armoured sea defences and a 2m high concrete wall. The boulders forming the rock armouring are devoid of vegetation. The seaward face of the concrete wall supports very occasional plants of Stag’s-horn Plantain (Plantago coronopus), Rock Samphire (Crithmum maritimum) and Sea-purslane (Atriplex portulacoides) as well as a colony of approximately thirty plants of Golden-samphire (Inula crithmoides). The sheltered north-facing side of the wall, including sections of concrete hard-standing, have been colonised by species typically associated with rocky shorelines. In particular, cracks and crevices provided a foothold for Rock Sea-lavender (Limonium binervosum agg.), Sea-plantain (Plantago maritima), Stag’s-horn plantain, Creeping-bent (Agrostis stolonifera), Red Fescue (Festuca rubra), Common Couch (Elytrigia repens) as well as occasional plants of Sea-thrift (Armeria maritima) and Rock Samphire.
Sheltered habitat beside the River Neath, at the northern end of Baglan Burrows and eastern end of Crymlyn Burrows SSSI supports saltmarsh dominated by Sea-purslane. Other species dotted within the sward included Common Saltmarsh-grass (Puccinellia maritima), Sea Aster (Aster tripolium) and Common Cord-grass (Spartina anglica). At the fringes of more established areas of saltmarsh, compacted sediment associated with creeks and hollows also support a community dominated by Annual Sea-blight (Suaeda maritima) and Purple Glasswort (Salicornia ramosissima).
No strandline communities were evident during a site visit undertaken late in 2012, indicating that the foreshore dunes at Crymlyn Burrows SSSI had been eroded during winter storms. However, a strandline and embryonic dune community supporting a mix of Sand Couch (Elytrigia juncea), Marram, Prickly Sandwort, Sea Sandwort (Honckenya peploides) and Sea Rocket (Cakile maritima) re-formed during the summer months. In terms of National Vegetation Classification (NVC), the SD2 Honckenya peploides-Cakile maritima strandline community and SD4 Elymus farctus foredune communities best describe the species assemblages that have developed since the winter. However, in places the rhizomes of Marram have colonised this pioneer zone and locally a SD6a Ammophila arenaria mobile dune Elytrigia juncea sub-community appears to best describe the first band of vegetation.
The foredunes throughout Swansea Bay support vegetation overwhelmingly dominated by Marram, interspersed by bare sand attributable to the SD6d Ammophila arenaria mobile dune (typical sub-community) of the NVC.
Dunes set back from the foreshore become increasingly fixed in character comprising Marram, Red Fescue, Common Bent (Agrostis capillaris), Sand Cat’s-tail (Phleum arenarium) and Thyme-leaved Sandwort (Arenaria serpyllifolia).
The grassland communities associated with Swansea Docks, particularly in the vicinity of the seawall where they are subject to sea spray during rough weather conditions, support species of upper saltmarshes. In particular, a narrow fringe of grassland beside the seawall along the south-western boundary of Queens Dock is dominated by Red Fescue and Sea Couch with very occasional tussocks of Long-bracted Sedge (Carex extensa), Sea Rush and Sharp Rush.
Grassland habitat along the south-eastern end of the seawall is sandy in places and supports occasional Marram. Typically, the sward comprises Common Couch and Red Fescue with varying cover of species including Creeping-bent, Cock’s-foot (Dactylis glomerata), Yorkshire-fog, (Holcus lanatus), Ragwort (Senecio jacobaea), Wild Carrot (Daucus carota), Wild Parsnip (Pastinaca sativa), Restharrow, Perforated St John’s-wort (Hypericum perforatum), Ribwort Plantain, Oxeye Daisy (Leucanthemum vulgare), Common Knapweed (Centaurea nigra), Common Bird’s-foot-trefoil (Lotus corniculatus) and Kidney Vetch. Analysis of quadrat data suggests elements of this habitat is broadly comparable to SD8 Festuca rubra-Galium verum fixed dune grassland habitat of the NVC although it is probably best described as a coastal grassland community.
|Ecosystem Processes||Metocean survey to measure currents, waves and turbidity. Coastal Processes, Sediment Transport and Contamination||Placement of metocean measuring equipment at two sites within the lagoon to measure currents, waves and turbidity||At site 1 generally low current speeds with a maximum of 0.42 m/s were recorded. Faster flows were found to occur on the ebbing tide |
Flows at site 2 were found to be slightly faster reaching a maximum of 0.52 m/s
Two sets of inshore wave roses created for each site. Waves recorded at the metocean sites show clear evidence of sheltering from Mumbles Head to long period westerly waves, with the predominant wave direction orientated further to the south than seen at the Scarweather Buoy, with much reduced wave heights in the shallower water. During the survey period the largest wave event at Site 1 had a significant wave height (Hs) of 1.7 m, an average zero crossing period (Tz) of 4.8s and a mean wave direction from 208°N. At Site 2, further offshore and in deeper water, the equivalent event resulted in a significant wave height of 1.87 m, Tz of 4.5s and a direction of 191°N
At Site 1, it can be clearly seen that turbidity values are considerably greater during spring tides than neaps. This increase is driven principally by the slightly higher flow speeds experienced over the spring tides, which would appear to be sufficient to remobilise fine sediments (mud) from the seabed.
Turbidity is typically greatest at Site 2 during peak current speeds, approximately 2 hours either side of LW over spring tides.
Based on the converted values, the mean near-bed SSC values were moderate to high at both sites, with a mean of 113 mg/l at Site 1 and 54 mg/l at Site 2. The generally higher concentrations at Site 1 are likely to be a function of the shallower environment within the surf zone, which tends to retain concentrations above 50mg/l. In comparison, concentrations at Site 2 tend to indicate lower concentrations during calmer periods, suggesting that some material may locally drop out of suspension.
Post-Installation Monitoring: Swansea Tidal Lagoon (SBTL)
|Stressor||Receptor||Study Description||Design and Methods||Results||Status|
|Collision||Marine Mammals||Monitoring of turbine collision risk for marine mammals||Monitoring of marine mammals will be undertaken following completion of construction of the Project. The results of the monitoring will be regularly reviewed and reported on an annual basis to ensure that the most appropriate collision risk mitigation package is in place. The content and duration of the monitoring programme will be agreed with NRW based on further discussion as part of the EPS licensing conditions. Monitoring may include detection of mammals using both surface detection (using a qualified Marine Mammal Observer) and an active sonar system. This combination was used successfully to monitor collision risk at Strangford Lough SAC (Royal Haskoning, 2011). For Strangford Lough active sonar relied on 24-hour a day manual monitoring. However, SMRU have recently been developing software for the detection and classification of marine mammals using active sonar which could be developed as part of an automated system (Hastie et al, 2012). |
The use of an acoustic deterrent device is proposed as a mitigation measure for the potential turbine collision risk (see Chapter 10 Marine Mammals and Turtles and Chapter 23 Mitigation and Monitoring).
To assess the potential noise effects of the operational turbines and the effectiveness of acoustic deterrents to reduce the risk of turbine collision, marine mammal reaction to generated noise could be quantified using both acoustic dataloggers and visual observation from survey vessels in the vicinity of site, using established guidelines.
Any collision events or near misses will be recorded and an appropriate reporting mechanism will be set up to report such events to the appropriate authorities and to inform the mitigation and monitoring protocols, as well as being reported annually. A strategy will be developed to locate any collided (injured or dead) animals and appropriate measures will be taken to deal with carcasses.
|Collision||Marine Mammals||Carcass surveillance||It is understood that at present any carcasses which are washed ashore tend to be reported and assessed. Within the monitoring programme identified above, the need for regular additional monitoring for carcasses, post mortem evaluation of carcass stranding and assessment of cause of death will be ascertained and linked into any existing programmes. Routine surveillance for carcases will be undertaken and liaison with the UK Cetacean Strandings Investigation Programme (CSIP) concerning existing shoreline surveillance which covers key areas which are predicted to be hotspots for strandings, based on local advice and hydrodynamic modelling. Integration of the Lagoon programme would be developed and run in coordination with the CSIP.||Planned|
|Collision||Fish||Survey for fish passing through the turbines||Surveys are proposed to assess fish pass through the turbines. Methods are currently being refined due to the complexity of sampling in areas of high flow, but it is considered feasible to position a small fishing vessel with a bass trawl downstream of a turbine and collect a number of trawls over a defined period. Flow from one turbine would be monitored. The fishing boat could be repositioned to monitor fish pass through the different turbines. |
An alternative method of survey would involve fixed position sonar. Devices such as Simrad SH80 omnidirectional fisheries sonar have been reliably used to detect and survey schools of fish such as herring up to about 400m in range in a circular pattern around a fixed point. These devices could be placed in a fixed position on the sea bed at 200 m outside the lagoon adjacent to the turbine array. They could be powered from the offshore O&M facility and set to continually store data back at this location. This survey method would have the benefit of continuous monitoring of fish and predator activity in relation to the turbines and would provide an unprecedented level of quality and continuity in monitoring fish populations, in a large area of the bay near the turbines.
A custom machine learning application would be an advantage with respect to analysis of the continuous streams of data that would be too large for a person to analyse by eye. This device could be used to categorically demonstrate avoidance behaviour and its effectiveness, and behaviour related to sound, or currents. These data would be invaluable to develop understanding and new science around the impact of the turbines and their effects on behaviour of marine animals. This device would also have the great advantage of storing the conditions and events leading to injury or death of marine mammals if this occurs and thus offers some potential for effective mitigation.
|Collision||Fish||Acoustic deterrents for fish collision||Chapter 9 of the ES proposes the use of acoustic deterrents to reduce the potential turbine collision risk. The Chapter identifies that noise surveys should be undertaken prior to installation of the devices. |
The sonar surveys outlined above could also be used to determine the effectiveness of acoustic deterrents, as well as passage of fish through the sluice gates when the deterrents are turned off during sluicing.
|Collision, Displacement, Habitat Change, Noise||Marine Mammals||Harbour porpoise usage surveys||A long-term acoustic monitoring programme for harbour porpoises is being established in the proposed Lagoon footprint and the wider Swansea Bay area. These surveys are being undertaken in 2014 to examine the use of Swansea Bay by harbour porpoises, and to determine if there are any seasonal patterns to usage. |
Two C-PODs were purchased by TLSB in 2013 and in conjunction with SEACAMS and they were deployed in November 2013 for an initial month of calibration. These C-PODs will be redeployed as part of this on-going study. The C-PODs will be positioned within the Lagoon footprint and outside the area to provide a control site. The survey will involve the use of in total four C-PODs, 2 at the lagoon site and 2 at a designated control site (off Mumbles), the exact locations will be dependent on mooring logistics and permit restrictions. Data will be collected on the presence and absence as well as foraging frequency and intensity for harbour porpoises. Monitoring will continue during construction and operation. Data will be analysed to determine daily and seasonal patterns. The results of the surveys will inform the subsequent monitoring strategies.
|Collision, Displacement, Habitat Change, Noise||Marine Mammals||Grey seal surveys||The C-POD data collection will be supported by additional surveys for grey seal. The initial scope of surveys will be developed in conjunction with SEACAMS. These could include boat based work or site surveys at potential haul out sites along the Gower.||Planned|
|Noise||Marine Mammals||Marine noise monitoring for pile drilling||Mitigation proposals for impact piling are described fully in Chapter 23 of the ES. These include the use of the JNCC (2010) protocol for piling activities (soft start procedure) if impact piling is required, the presence of a Marine Mammal Observer and the use of passive acoustic monitoring. |
Marine noise surveys at key receptor locations will be undertaken for impact piling as outlined in the noise section of this report. If impact piling is required, and there is sufficient advance notice available, additional marine mammal observers would be based on survey vessels in the vicinity of the site, as well on strategic locations in the bay. This would allow the extent of behavioural change and relative abundance to be assessed before and during noise generating activities. JNCC protocols for observation will be followed.
|Attraction, Avoidance, Habitat Change||Marine Mammals||Otters||Proposed mitigation measures to ensure potential impact to Otters is minimised include avoidance of light spill onto open water of the docks and exclusion of high risk construction areas whilst maintaining access for Otters between the docks estate and coastline. These proposals will require monitoring during the construction phase. |
Trail cameras (remote cameras triggered by movement or passive infra-red) will be employed in addition to searches for spraint, in the three years post-construction to confirm / identify the continued use of the area by otters.
|Habitat Change||Fish||Intertidal and subtidal ecology - oysters||Oysters stored in CSAR will be relocated to the spatting ponds constructed as part of the Project. The successful production of offspring from oysters in spatting ponds is affected by many variables, including site specific factors and the condition of the oysters. As such the oyster enhancement programme will be adapted. |
The production of spat in hatcheries is a well-documented process. However, the physiological condition of oysters differs and the process has to be trialled and optimised. The preliminary aim is to stock 3-5 discrete areas inside the Lagoon with oysters from the spatting ponds and/or hatchery. The exact location depends on sediment and hydrodynamic conditions within the lagoon. It is anticipated that there will be suitable subtidal areas, but possibly also intertidal areas; in Swansea Bay native oysters are naturally found in lower intertidal areas, although in low numbers.
In order to create control areas, ideally it would be proposed to stock a similar number of sites outside the lagoon, but inside the application boundary area. However, if possible other sites with different environmental conditions could be considered within the wider Bay, although the feasibility of this will be discussed with the appropriate authorities at the time. The growth and survival of oysters inside and outside the lagoon will be monitored by boat sampling and underwater cameras. The extent to which the created oyster reefs support biodiversity compared with other habitats will be assessed.
TLSB seeks to undertake research in collaboration with SEACAMS and Swansea University to address current knowledge gaps. With regard to oysters this could be questions regarding their impact on water quality and algal composition, effects of harmful algal blooms (HABs) or climate change related issues such as ocean acidification (OA) and the calcification of shells. As with the water quality the Lagoon has the potential to be a “living laboratory”.
The development of a method that utilises a tidal lagoon for the creation of oyster reefs will depend on a series of experiments and optimisation stages. Each stage may have to be adapted to site specific conditions, technical feasibility and nature conservation requirements. However, the longevity of the tidal lagoon allows a step-by-step adaptive process and TLSB aspires to develop a procedure that can be transferred to other lagoons or similar structural developments. If successful the method could be rolled out to assist oyster restoration programs in other areas.
|Habitat Change||Fish||Fish surveys||Further fish surveys are proposed for the operational phase of the Project based on the methodologies and sampling locations used for the baseline and pre-construction surveys. The scope of the surveys would be further refined in consultation with NRW based on the findings of the ES and the surveys undertaken pre-construction as described above. The findings would be analysed taking into consideration long term data sets and other routine and non-routine sampling undertaken in the Bay. |
The scope of these surveys would also consider that the construction of the lagoon seawalls will afford increased spawning, juvenile, foraging and refuge habitat to a variety of species of fish and invertebrates. It is proposed that the surveys would also be designed to assess the colonisation and development of the lagoon seawall (reef) and the diversity and abundance of associated fish fauna.
It is proposed to undertake a suite of surveys within the range of habitats created by the Project that include fine sediment environments of the inner lagoon, sub-tidal rocky habitats and intertidal rock pools.
Surveys may include: i. Fine sediment environments: potential use of beach seining, push nets, small beam trawls, drop trapping and fyke netting ii. Subtidal Rocky Habitats: potential use of fyke netting, trapping, diving transects and baited remote underwater video (depending on turbidity of water and spatial scale of surveys required). iii. Intertidal rockpools: sampling by anaesthetisation, hand netting and visual assessment.
|Habitat Change||Fish||Herring spawning ||Artificial spawning material for herring shoals that are currently known to spawn within the Bay will be provided at the base of the seawalls (see Chapters 9 and 23 of the ES). It is proposed to monitor the artificial spawning medium and a number of techniques are being considered including: i. Placement of artificial substrate that can be readily removed and assessed ii. Direct observation by diving and observers iii. Fixed transect monitoring by divers iv. Drop down cameras (depending on turbidity of the water) v. Sonar – fixed and vessel based.||Planned|
|Habitat Change||Fish||Predation and reefing||The construction of the Lagoon seawall along the dredged navigation channels of the Neath and the Tawe is designed to increase fish fauna productivity of the near shore environments. However this may in turn result in the increased predation of emigrating juvenile salmonid fish. |
Monitoring of birds before and after construction within the vicinity of the Project would assist in the assessment of the potential impacts of the Project upon fish stocks. Seasonal observation of the abundance and diversity of fish eating birds in the vicinity of the Project, recording foraging activity would provide information to assess this effect. Data has already been collected during coastal bird surveys undertaken as part of the baseline EIA and further surveys are proposed for the operational phase as described in Chapter 9.
Predatory species may be attracted to the reef environment of the lagoon walls as a result of the increased productivity of prey species resulting from the design of the complex and heterogeneous environment. Migratory juvenile fish may concentrate along these walls as they move out of the estuaries, running the length of the new reefs that will afford enhanced habitat and foraging grounds for cryptic or pursuit predators such as e.g. bass. The seasonal abundance and diversity of fish eating fish complimented with stomach analysis to determine diet would contribute to an understanding of the impact these predators may have on emigrating migratory fish.
It is proposed that data be collected from anglers using the seawall on both an ad hoc basis as well as during angling competitions. Data collected would include species, weight and length as well as stomach content if possible.
In addition to this, seasonal surveys to determine catch per unit effort of predatory fish species will be considered as a means of collecting further data. If progressed, stomach analysis from a sample of the predators encountered will be undertaken to determine prey items.
|Habitat Change||Fish||First Movements of Salmonid Smolts and Smolt Behaviour in the Bay||It is proposed to consider survival of salmonid smolts in the lower reaches of the River Tawe and during their first forays into the marine environment. It is perceived that the Tawe Barrage has removed migratory cues within the lower river that delays passage into the marine environment. It is known that there is a limited window of opportunity for smolts to successfully make the transition from freshwater to marine environments and delays to their migration may significantly reduce the marine survival of these subadults making them more prone to predation. Further the dispersal and behaviour (i.e. swimming speeds) of smolts in to the Bay is not fully understood. Enhanced understanding of this component of their life history would enhance the power of models such as the IBM currently used to predict the behaviour and fate of fish both in Swansea and at future developments, as well as validating some of the rule sets applied to these species within these models. The patterns of migration of smolt from the River Neath and River Tawe are likely to be well captured in the IBM, because the currents are well defined and the smolts are relatively weak swimmers and thus at the mercy of currents to a high extent. It is evident, based on the coastal processes of the area that all the smolts exiting Swansea Bay and heading to the sea will pass closest to the coast just south of the Mumbles. Therefore there is an opportunity to reliably monitor their movements at some distance from their natal river mouths by placing acoustic transceivers in this area. |
A potential survey method that could be employed and which will be investigated further comprises: i. capture of smolts at Tawe Barrage; ii. apply acoustic tracker, iii. release after habituation to marine water iv. deploy acoustic transceivers within Bay v. monitor movement within and external to lagoon.
The transceivers could potentially be placed at the exit to the river (to monitor leaving, waiting and returning smolts), at the entry to the turbines and sluice gates, inside and outside the lagoon, and off the south of the Mumbles. If implemented the survey would be undertaken once in the first three years of operation and the results reported within the annual report.
|Habitat Change||Fish, Invertebrates||Intertidal and subtidal ecology. Surveys of seawalls – intertidal and subtidal and invasive species||The intertidal section of the seawalls will be monitored. A number of representative transects of the wall will be fixed as permanent monitoring sites at various locations around the lagoon, with differing levels of exposure. The colonisation process will be monitored by photographic recording and mapping of a 0.5m corridor from the upper intertidal to lower intertidal area. Initially transects will be monitored twice per year in spring and autumn, and after two years the monitoring frequency will be reduced to once per year for the following 3 years. |
Once the walls are completed divers will be used to carry out a survey of the submerged sections of the lagoon wall. The visibility in Swansea Bay is generally poor and diving will only be possible after several days of dry weather with little run-off from the catchment areas, and after periods of calm weather. Underwater cameras will be deployed either stationary or from a RIB to record motile fauna at the foot of the lagoon wall. Special attention will be paid to crustacea and fish. The results of this survey will be evaluated and if effective the survey will be repeated in Year 3 and Year 5 operation. Thereafter the need for further survey would be determined.
The intertidal and subtidal surveys discussed above will check for the presence of nonnative marine species. Additionally there will be a general walk-over survey once per year paying particular attention to key species such as the Pacific oyster or invasive seaweeds, to reduce the risk that such species are missed in the transect surveys. Any records will be immediately reported to the statutory authorities. Swansea Bay is already colonised by invasive species such as the barnacle Elminius modestus, which is likely to colonise the rock armour. Special attention will be paid to invasive species not currently recorded in Swansea Bay. Appropriate measures will be established for any invasive species found to be present. These measures will depend on the nature of the species, and whether the species is exclusively found associated with the lagoon or in the wider coastal area.
|Habitat Change||Physical Environment, Fish, Invertebrates||Intertidal benthic ecology||Monitoring of intertidal habitats will be undertaken in year 1 following the completion of construction and again 5 years following completion, to validate the impact predictions made in the ES. Survey methodology will follow those undertaken during the baseline surveys for ease of comparison of results. Assessment of the results will be reported 6 months post survey. Particular focus will be made of the extent and quality of protected features, including Sabellaria extent both within Swansea Bay, within the lagoon and lagoon walls and at translocation sites.||Planned|
|Habitat Change||Physical Environment, Fish, Invertebrates||Benthic surveys||Subtidal surveys will be repeated at the twenty sites identified above in order to assess change. The survey methodology used in the EIA will be repeated in year 1 following completion of construction and again 5 years following completion. The need for further surveys will be considered in the relevant annual report. Replicated samples will be collected analysed from the 20 sites for PSA and infauna. Metals (Aluminium, Arsenic, Barium, Cadmium, Chromium, Copper, Iron, Mercury, Nickel, Lead, Tin, Vanadium, Zinc, Total Petroleum Hydrocarbons, Tributyl Tin) will be analysed at 10 of the sites.||Planned|
|Habitat Change||Birds||Coastal birds - Core and low tide counts||The Lagoon construction programme is due to commence when the main over-wintering bird interest of Blackpill will have declined. As such monthly surveys will first be targeted around the east side of the bay (as per the baseline summer surveys). These surveys will continue from commencement of construction year 1 to end of summer year 2. |
The monthly surveys will be extended to the west side of the bay for the over-wintering period year 1 to year 2. This data will be used to provide a comparison between baseline data and birds using habitat during the construction phase. The results of the survey will be reviewed and the need for surveys in the following years will be ascertained.
Monthly winter surveys will be undertaken in order to provide a comparison between baseline data and birds using habitat during the construction phase. Core and Low Tide Counts will be undertaken between October and March in years 1, 3, 5 and 10. These will be reported in the ensuing annual reports.
|Habitat Change||Invertebrates||Post-construction habitat survey||A number of section 42 NERC 2006 invertebrate species were identified from the docks estate during baseline surveys. Additionally, Crymlyn Burrows is notified for invertebrate assemblages as well as presence of the strandline beetle (Eurynebria complanata). |
Post-construction survey of habitats within the Project will be undertaken by the Lagoon Warden on an ad hoc basis but specific surveys will also be commissioned to determine the colonisation of intertidal habitat as well as coastal grassland habitat in years 1, 2, 3, 5, 7 and 10.
|Habitat Change||Reptiles||Monitoring surveys||The effectiveness of the reptile mitigation strategy will be monitored including subsequent colonisation of habitat associated with the Project. Given public access within areas likely to support reptiles, monitoring surveys may involve visual assessments rather than surveys, using techniques such as tinning, that are often disrupted by members of the public.||Planned|
|Habitat Change||Bats||Survey of bats and foraging habitats||In order to confirm the continued use of foraging habitat by bats, it is proposed that remote bat detectors (anabats) are deployed for at least a week duration, bi-annually (between May and September), for three years post-construction. In addition, use of the lagoon wall by foraging bats could also be determined over the same time period using a hand-held bat detector.||Planned|
|Habitat Change||Physical Environment||Notable plants||The operational monitoring of notable plants species will include those of rocky shore vegetation (including Golden-samphire) but also the colonisation of habitat within the Project by others. Monitoring is likely to comprise visits at an appropriate season in years 1, 2, 3, 5, 7 and 10 post-construction. The monitoring may include fixed point photography.||Planned|
|Changes in Flow||Ecosystem Processes||Photographic record of coastal processes||Photographic records will be taken of the outside of the eastern seawall adjacent to Crymlyn Burrows and along the western seawall as they are formed. This will provide a simple visual recorded of potential sediment deposition or erosion patterns along the new seawalls. Photographs will be taken from a fixed point on a monthly basis at Low Water Springs. The need for specific profiles or recording at these locations during operation will be determined based on review of the photographic records. |
The photographic record will be analysed and reported to NRW, CCSC and NPTCBC on an annual basis. The annual report will recommend whether specific profiles or recording should be undertaken. Where such profiles or recording is undertaken it will be contained in the annual report.
|Changes in Flow||Ecosystem Processes||Beach profiles||Beach profiles within Swansea Bay are currently monitored annually by Swansea and Carmarthen Bay Coastal Engineering Group (SCBCEG) (see Figure 4.1). A high level overview of existing data gathered by SCBCEG for the sites within Swansea Bay between Mumbles and Kenfig Burrows was undertaken for the EIA. More detailed analysis will be carried out of beach profile data recorded at Kenfig Burrows (profile 228), Aberavon Sands (profile 220), Crymlyn Burrows SSSI (profiles 214 and 215), Swansea Beach (profile 208 or 209), Blackpill SSSI (West Cross profile 205 and Lower Sketty profile 206) (see Figure 4.1). It is proposed that beach profile data collected by SCBCEG is analysed at these sites after each recording event to assess any changes to beach profiles outside of natural variation. The analysis will be contained in the annual report. |
The need for TLSB to carry out its own monitoring at any of these sites will be identified if ongoing monitoring by SCBCEG is not undertaken or if the reported results indicate that additional assessment is required. Particular attention will be paid to any accretion at Crymlyn Burrows SSSI and potential erosion at Blackpill SSSI (see Chapter 6 Coastal Processes, Sediment Transport and Contamination). The need for beach replenishment at Blackpill SSSI will be considered based on this analysis.
|Changes in Flow||Ecosystem Processes||Wave reflection and currents||It is proposed that Nortek Acoustic Wave and Current (AWAC) devices will be deployed over continuous tidal periods to collect data on waves, water levels, current profiles and suspended sediment (acoustic backscatter), combined with Optical Back Scatter (OBS) for suspended sediment (turbidity). The devices will be deployed to obtain three months of oceanographic field data at two locations in the first year of operation. Site 2 is located within the lagoon footprint. |
It is proposed to locate a further AWAC device at a new site, Site 3, at a point outside the lagoon footprint. The location of Site 3 will be determined in consultation with NRW subsequent to micro-siting of the turbine and sluice gate housing structure and it will be positioned in order to collect flow data resulting from the physical presence and operation of the Lagoon, together with data that can be used to assess wave reflection. Current navigational movements around the bay will also be taken into account when selecting Site 3. Depending on the final position, the need for additional data collection of flows through the turbines will be determined.
|Changes in Flow||Ecosystem Processes||Currents from turbines and sluice gates and suspended sediments||An alternative method to collect data on flows through turbines and sluices could be undertaken by using a vessel mounted Acoustic Doppler Current Profiler (ADCP). This would provide spatial current data as opposed to fixed point temporal data which is collected by the AWAC deployments. The spatial ADCP survey could also be used to provide more detailed information on flow patterns within the lagoon as a whole, as well as to measure backscatter intensity, which would provide an indication of turbidity in the water column.||Planned|
|Changes in Flow||Ecosystem Processes||Bathymetric surveys - siltation within the lagoon and navigation channels||It is proposed to undertake bathymetry surveys to assess the levels of siltation within the lagoon footprint. The surveys will comprise a single beam bathymetric at 50m line spacing within the lagoon boundary to inform any bed level changes. It is proposed to carry out the surveys annually for three years after completion of the works and then the frequency of surveys will be reviewed after the third year. The first such single beam bathymetric survey would coincide with the “objects on the seabed” survey and it would form the revised baseline for the operation phase surveys. |
Where the results of bathymetry survey indicates that additional surveys to calculate volumetric variations within the lagoon are appropriate to assist dredge work, surveys with a tighter line spacing (10-20m) within the lagoon would be proposed. This information will be used to develop and refine the maintenance dredging strategy.
|Physical Environment||Multi-beam bathymetric surveys and side-scan sonar||Multi-beam bathymetric and side scan sonar surveys are proposed within the Lagoon footprint and a 250m wide corridor around the outside of the marine works to identify any objects that may have been left on the seabed during the construction phase of the Project. The proposed line spacing is 40m with multi-beam echo sounders used to infill at 10-20m line spacing for shallower areas. It is proposed that this survey will take place as soon as is feasible following completion of construction.||Planned|
|Physical Environment||Terrestrial ecology - Coastal grassland, sand dune and saltmarsh||Checking of any turfs/topsoil (e.g. are they sufficiently watered/covered) will continue until the time that supervised translocation of species-rich grassland/movement of topsoil will take place. A monitoring programme will be drawn up throughout the construction phase to assess the success of the translocation/reuse of topsoil mitigation. This is likely to involve a period of visits which will gradually reduce in frequency in response to monitoring findings. Remediation measures will be put in place should monitoring reveal that the mitigation is not working, including weed control, watering and re-seeding with native species. |
An operational monitoring programme will be drawn up in conjunction with the relevant stakeholders. This is likely to comprise monitoring at an appropriate time of year in years 1, 2, 3, 5, 7 and 10 post-construction. The monitoring may include fixed point quadrats and fixed point photography.
Management may be required should monitoring reveal that habitat creation is not being effective, for example ineffective tidal flooding.
|Physical Environment||Invasive species||The operational monitoring programme will include surveillance visits to those areas where invasive vegetation control has taken place, to ensure efficacy (particularly relevant for Japanese Knotweed) in years 1, 2 and 3 post-construction. Infestations will be dealt with promptly within land under Project control.||Planned|
|Human Dimensions, Recreation & Tourism||Angling / recreational fishing||Angling opportunity and desirability to fish from the lagoon wall may be assessed both by angler surveys (creel census) or by multiple fixed CCTV. Time lapse images of the latter can be analysed to determine the density of anglers, tide or time of day preference, type of angling experience afforded i.e. static fishing on the bed, float fishing or spinning. Method of angling may often be used to determine target species. |
Angler “surveys” would be encouraged in that anglers using the lagoon seawall are to be requested to record their catches. These “surveys” could be implemented as part of licence conditions for anglers using the seawall. In addition, it is proposed to hold angling competitions and for information about fishing effort and fish caught e.g. numbers, species, size, etc. to be recorded.