Application of Marine Spatial Planning tools for tidal stream farm micro-siting

Application of Marine Spatial Planning tools for tidal stream farm micro-siting M. Álvareza, V. Ramosb,c,∗, R. Carballoa, I. Lópeza, D. M. Fouza, G. Iglesiasd,e aUniv. de Santiago de Compostela, Área de Ingeniería Hidráulica, EPSE Campus Univ. s/n, 27002 Lugo, Spain bFEUP-Faculty of Engineering of the University of Porto, Department of Civil Engineering, rua Dr. Roberto Frias, s/n, 4200-465 Porto, Portugal cInterdisciplinary Centre of Marine and Environmental Research of the University of Porto, Terminal de Cruzeiros do Porto de Leixões, Avenida General Norton de Matos, S/N, 4450-208 Matosinhos, Portugal dMaREI, Environmental Research Institute School of Engineering, University College Cork, Ireland eSchool of Engineering, University of Plymouth, United Kingdom Abstract The operation of tidal stream energy farms may interfere with other uses of the marine space, especially in depth-limited areas (estuaries, rivers, etc.) which are typically subject to multiple demands of use. The Marine Spatial Planning Directive (MSP) was passed by the European Commission in 2014 to ensure a harmonic coexistence between different maritime activities and to protect the marine environment. In this context, the objective of this work is to present a methodology based on MSP tools for tidal-farm siting in depth-limited areas. The methodology is illustrated through a case study: Ria de Ribadeo, a shallowwater estuary in NW Spain. Having considered a number of uses (archaeological, biodiversity, fishing, aquaculture, recreational and navigation), two exploitable tidal farm sites (Areas A and C) with annual energy densities of 1 𝐺𝑊 ℎ𝑚−2were found. The estuary is periodically dredged to maintain navigation. Dredgingrelated risks were analysed using a novel indicator, the Dredging Associated Risk (DAR), based on which Area C was discarded and Area A had its exploitable surface area reduced by 25%. In sum, the methodology proposed was proven to be effective for tidal stream farm planning. ∗Corresponding author Email address: [email protected] (V. Ramos ) Preprint submitted to Ocean & Coastal Manegment December 8, 2021 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Keywords: Depth-limited tidal sites, Good Environmental Status (GES), Maritime Planning System, Dredging Associated Risk (DAR), Ria de Ribadeo 1. Introduction With the aim of mitigating climate change and reducing fossil fuel dependence, from the beginning of the 21𝑠𝑡 century, different policies have been developed, initiating a transition towards a non-polluting and sustainable energy model. Examples of those policies are: (i) the Paris Agreement (United Nations) [1], (ii) the 2030 Agenda for Sustainable Development (United Nations) [2] and (iii) the EU 2030 Framework for Climate and Energy (European Union) [3]. The latter aims to increase the share of renewables up to 32% of the EU’s energy consumption and, cutting Greenhouse Gas (GHG) emissions by 40% compared to 1990 levels [4]. In this context, Marine Renewable Energy (MRE), which presents an abundant and geographically-diverse resource (up to 32 TW) [5], is expected to play an important role to achieve the aforementioned goals. For this purpose, in 2015 the EU Commission created the Ocean Energy Forum, with the objective of developing strategic road-maps for the development of a MRE industry. Consequently, a year later, the road-map Building ocean energy for Europe was released [6], identifying that: (i) MRE could supply up to 10% of EU’s energy demand by 2050, (ii) diversification of the EU’s low-carbon generation capacity is required to achieve the goals in terms of GHG emissions; (iii) MRE exploitation may reduce significantly GHG emissions (up to 276 𝑀𝑡 𝐶𝑂2𝑒annually) by 2050, and (iv) MRE represents a fantastic opportunity to develop a new industrial sector, boosting EU’s economy and contributing to the long-term sustainability of its coastal regions. Within the large variety of MRE sources, tidal stream energy, with an estimated global resource of 120 GW [7], stands out. Tidal stream energy is characteristic of coastal regions, where tidal height variations combine with the morphological conditions, to produce tidal currents [8]. Consequently, the kinetic energy stored in the tidal currents is used for electricity generation, by means of Tidal Energy Converters (TECs), which are placed directly into the flow [9]. In this context, the main advantages of tidal stream energy are: (i) renewable nature and high predictability of the resource [10] (ii) high load factors associated to tidal currents [11] and (iii) non-existence of extreme flows that could jeopardise the long-term survivability of submerged TECs (i.e. tidal streamsvelocities rarely exceed 6 𝑚𝑠−1) [11]. Despite all these facts, tidal stream energy is far from being commercially viable for large-scale electricity generation [12]. On these grounds, the following 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 facts stand out: (i) despite recent breakthroughs (MeyGen tidal energy project [13]), TEC technology is not yet mature, (ii) few locations around the world meet the requirements in terms of tidal flow velocities (> 2 𝑚𝑠−1) and water depths (> 25 𝑚) for the operation of the first and second generation of TEC concepts [14], (iii) TEC operation usually takes place in harsh marine environments, which increases significantly the difficulty and costs of installation and maintenance operations [12], (iv) operation of TECs may cause significant disruptions of different marine environmental processes such as transient and residual circulation patterns [15], transport of suspended matter (e.g. pollutants [16], nutrients [17] and sediments [18]) and ambient turbulence conditions [19], and last but not least (v) potential interactions with other marine uses such as navigation [20], fishing, aquaculture [21] and recreational activities [22]. The latter highlights the necessity of managing the different maritime uses and activities (MRE, fishing, aquaculture, recreational and others) using a holistic approach. For this purpose, in 2014 the EU released the 2014/89/EU Directive on Maritime Spatial Planning (MSPD) [23], whose main objectives are: (i) reduce conflicts and create synergies between different maritime uses [24], (ii) set a clear and predictable legal framework to attract investments in maritime activities [25, 26], (iii) increase cross-border cooperation between EU Member States [27] and (iv) ensure the protection of the marine environment by identifying impacts and opportunities for multiple maritime uses. Consequently, EU Member States had to transpose Directive 2014/89/EU into their national law by 2016 and define their respective Maritime Spatial Plans (MSPs) by 2021. Regarding MRE exploitation, MSPD offers the opportunity to improve and harmonise the legal framework for licensing MRE projects, increase legal security for MRE stakeholders and, reduce and arbitrate conflicts with other maritime users [28]. For the specific case of Spain, Royal Decree 363/2017 [29] transposes Directive 2014/89/EU into the Spanish national law. RD 363/2017, in its general provisions and article 10, includes the exploitation of MRE within the different maritime uses to be considered for the elaboration of future MSPs. For each of the Spanish marine demarcations, MSPs are still under development (currently in the public consultation stage) and they are expected to come into force by the end of 2021 or early 2022. MSPs will follow a hybrid planning approach with the aim of ensuring a seamless coexistence between maritime uses and activities, while ensuring a Good Environmental Status (GES). For this purpose, MSPs identify the so-called priority use areas, for which a set of rules and provisions are defined to avoid that the main use of the area is not compromised by other marine activities. In consequence, proposals for other marine activities must demonstrate compatibility 3 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 with the priority use of the marine area. On these grounds, planning the installation of tidal farms will require a detailed (i) spatial identification of different maritime uses and (ii) assessment of the potential impacts caused by other marine activities on the operating conditions of tidal farms, and vice versa; with the purpose of ensuring an harmonic coexistence among the different maritime uses of the area of interest. As a result, Marine Spatial Planning will contribute to decrease the level of uncertainty of tidal energy projects, decreasing interactions with other marine activities and enhancing legal certainty [28]. Further details on the Spanish maritime legislation can be found in Section 2. The technological development of TECs, has brought the opportunity of exploiting the tidal stream energy resource in a wider variety of coastal locations, especially at shallow tidally-driven estuaries and rivers [30], which also host of multitude of marine uses (shipping, fishing, aquaculture and recreational activities). Moreover, the tidal stream resource at depth-limited regions is highly sensitive to natural (sediment transport) and/or anthropogenic (dredging of navigation channels) bathymetric changes [31]. Consequently, the holistic approach of Marine Spatial Planning appears as an excellent tool for tidal farm siting, especially in those regions. Previous research has dealt in detail with the optimum siting of tidal stream energy farms, considering different constraints such as available resource [14], maintenance [32], operating costs [33], power production [34], layout optimisation [35], environmental impact [36] and economic viability [37]; however, few works have applied Marine Spatial Planning in depth to find the optimum location for tidal farms [38, 39, 40]. Against the foregoing backdrop, the objective of this paper is to present a methodology based on Marine Spatial Planning with the aim of finding the most suitable location for the installation of tidal farms in depth-limited regions, using for this purpose Ria de Ribadeo (Figure 1), a shallow and highly energetic estuary locatedin NWSpain[41], ascasestudy. Theremainder ofthispaperis structuredas follows: Section 2 presents the main characteristics of the Spanish legal framework for maritime activities. Section 3 describes in the detail the maritime uses and characteristics of Ria de Ribadeo. Section 4 presents the Dredging Associated Risk (DAR) indicator for depth-limited tidal sites. Section 5 illustrates the application of Marine Spatial Planning for tidal farm siting in Ria de Ribadeo. Finally, conclusions are drawn in Section 6. 4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 2. Spanish Maritime Legal Framework Spain, as any other EU Member State, legislates the protection of marine environment and management of maritime activities, according to: (i) Directive 92/43/EEC on nature conservation [42], (ii) Marine Strategy Framework Directive 2008/56/EC (MSFD) [43] and (iii) Maritime Spatial Planning Directive 2014/89/EU (MSPD) [23]. In May 1992, the European Council approved Directive 92/43/EEC on the conservation of natural habitats and wild fauna and flora, establishing the EU Natura 2000 ecological network of protected areas (Sites of Community Importance, SICs), preserving them against potentially damaging developments. EU Commission Decisions 2004/813/EC [44] and 2006/613/EC [45] define the SICs for the Atlantic and Mediterranean biogeographical regions of Spain, respectively. In this context, Law 42/2007 [46], which transposes Directive 92/43/EEC into the Spanish domestic law, establishes in its article 42.3 that Spanish autonomous regions have a period of six years to declare the SICs, which belong to their jurisdiction area, as Special Areas of Conservation (SAC) and/or Special Protection Areas for Birds (SPAB) and to elaborate managing and monitoring plans for those areas. In June 2008, the European Parliament approved the Marine Strategy Framework Directive 2008/56/EC (MSFD) [43], which aims to preserve the marine environment and to ensure its long-term sustainable use. MSFD was transposed into the Spanish national law in December 2010, by means of Law 41/2010 [47], whose main goal is to achieve GES in the marine environment. To this end, specific strategies for each Spanish marine demarcation were developed, proposing coherent planning of activities and uses of the marine environment compatible with the preservation of its biodiversity. Marine strategies are subject to be revisited every six years. In addition, Law 41/2010 creates the Network of Marine Protected Areas (NMPAs), setting the mechanisms for their designation, preservation, environmental monitoring and management of marine activities. Examples of MPAs are areas belonging to Natura 2000 network (SICs, SPAs and SPABs), World Heritage and Biosphere Reserve UNESCO areas [48] and Ramsar [49] and OSPAR [50] sites. RD 363/2017 [29], of April 2017 transposes Maritime Spatial Planning Directive 2014/89/EU (MSPD) into the Spanish law, establishing the legal framework for the management of marine spaces. For this purpose, RD 363/2017 contemplates the elaboration of Marine Spatial Plans (MSPs) for each of the Spanish marine demarcations, with the aim of ensuring a sustainable development and 5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 harmonic coexistence of marine sectors and protection of the marine environment. For this purpose, RD 363/2017 establishes the guidelines for the elaboration and revision of MSPs. However, it does not establish either priority criteria for the execution of maritime activities or rules to arbitrate conflicts between different maritime users [28]. Regarding the exploitation of Marine Renewable Energy (MRE), RD 363/2017 highlights in Article 5.c the need of producing energy from MRE sources to foment a sustainable development of coastal regions, while Article 10.2 includes MRE exploitation among the maritime activities to be considered for the elaboration of MSPs. As aforementioned, MSPs, which are currently under public consultation, are expected to come into force by the end of 2021 or early 2022, and will be susceptible to revision, every ten years. Overall, MSPs will follow a hybrid planning approach, prioritising the coexistence of multiple marine activities in the same marine space, as well as ensuring its GES. Nonetheless, priority use areas will be defined and, therefore, proposals for other marine activities must demonstrate compatibility with the designated use of the area. It is worth noting that protected marine areas are classified by the MSPs as priority use areas for the preservation of biodiversity and will be regulated according to the legislation applicable to them. Finally, high-potential areas will be also identified, giving priority to uses and activities, which present a high-future development [51]. Additionally, RD 1028/2007 [52] regulates the licensing process of MRE installations in the Spanish jurisdictional waters. RD 1028/2007 contemplates the commercial licensing only for off-shore wind farms, while for other types of MRE it establishes a simplified licensing procedure for experimental installations. RD 1028/2007 also classifies the Spanish littoral in appropriate and non-appropriate areas for the installation of off-shore wind farms, based on an environmental impact assessment carried out by the inter-ministerial commission of Marine Environment, Industry and Tourism. On these grounds, it is expected that MRE exploitation areas proposed by RD 1028/2007 will be overruled by future MSPs [53]. Furthermore, future regulatory changes are expected to streamline licensing procedures of MRE plants [53, 54]. Finally, Figure 2 shows the linkages among the different legislation presented in this section. 3. Characterisation of maritime exclusive areas for Ria de Ribadeo Ria de Ribadeo is a shallow coastal embayment, with a total surface area of approximately 10 𝑘𝑚2, located in NW Spain (Figure 1). Its location, naturally sheltered from the harsh marine environment of the Bay of Biscay, has prompted 6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 a significant development of different maritime uses such as aquaculture, tourism and recreational activities. Ria de Ribadeo also acts as a natural border between the autonomous regions of Galicia and Asturias (Figure 1), housing a multitude of commercial and trading activities throughout the ports of Ribadeo and Figueras (Figure 1). In addition, Ria de Ribadeo presents remarkable biodiversity and archaeological heritage [49]. Finally, Ria de Ribadeo has an abundant tidal stream energy resource [41], with three potential tidal sites identified at the middle ria [31], whose exploitation could bring a fantastic opportunity for the development of a new industrial sector in the region. However, the exploitation of the tidal resource could interfere with the particular marine environment [56] and biodiversity of the ria [57] and with other relevant socio-economic activities such as aquaculture and marine navigation [58]. Moreover, periodic dredging operations of the approach channels of Ports of Ribadeo and Figueras alter the hydrodynamic patterns of the ria [31]. Consequently, the available resource and operating conditions of tidal farms could be drastically modified, jeopardising their long-term viability [31]. In this context, before planning the installation of a tidal farm in Ria de Ribadeo a holistic approach is necessary, considering the potential interactions of tidal farm operation with the maritime uses of the ria, which are described in detail from Sections 3.1 to 3.6, using for their definition, GIS spatial analysis (Figures 3 to 5). 3.1. Special Areas of Conservation (SAC) and Special Protection Areas for Birds (SPAB) Decision 2004/813/EC identified Ria de Ribadeo as a Site of Community Importance (SIC) within the Atlantic biogeographical region [59]. As mentioned in Section 2, Law 42/2007 establishes that the Spanish autonomous regions should classify SICs, lying inside their jurisdiction areas, as SACs and/or SPABs. Therefore, the parliament of Galicia approved Decree 37/2014 [60], which identified 59 SACs and 16 SPABs, and also proposes managing and monitoring plans for those areas. In this context, Ria de Ribadeo was classified as SPAB (ref. ES0000085 [61]), and as SAC (ref. ES11200002 [60]) within the estuary/wetland category. As a result, Ria de Ribadeo is included in the Spanish Network of Marine Protected Areas (NMPAs) [62]. Decree 37/2014 classifies both SACs and SPABs into three different categories: (i) protected areas, in which only traditional activities with little to no impact on ecosystems are allowed, (ii) conservation areas, where traditional and non-traditional activities compatible with the local ecosystems could be carried out and (iii) general use areas, in which industrial activities may be allowed after a detailed environmental impact assessment. 7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Figure 3 shows the spatial distribution of the aforementioned areas across Ria de Ribadeo. It can be observed that in the mouth of River Eo, there is a protected area, which covers a surface of 160 ℎ𝑎. The inner and outer sections of the ria are marked as conservation areas, spanning a total surface of 392 ℎ𝑎. Conversely, the middle section of the ria (80 ℎ𝑎) is declared as a general use area. Furthermore, it is worth noting, that RD 363/2017 and, consequently, MSPD applies only for the outer section of the ria, since their inner and middle sections lie in the category of transitional waters (Figure 3). In this context, the draft version of the MSP for the North-Atlantic Spanish demarcation classifies the outer section of Ria de Ribadeo as a priority use area for the preservation of biodiversity [55], highlighting Decree 37/2014 as the applicable legislation to manage maritime activities. All in all, and despite the inner and middle sections of the Ria de Ribadeo lie outside the scope of RD 363/2017, the tools provided by MSP are still very valuable to find the optimum location of tidal farms in the area of study. 3.2. Archaeological protected sites Ria de Ribadeo presents an outstanding archaeological heritage. A multitude of archaeological remains, from centuries XVI to XVIII belonging to merchant and war ships, have been found in the outer and middle sections of the ria (Figure 4). Considering the large number of documented shipwrecks in the ria, further archaeological wrecks are expected to remain undiscovered, especially in the surroundings of the marina harbour, which coincides with the historical location of the port. Table 1 summarises the main characteristics and archaeological value of the wrecks found in the ria. In this context, Law 5/2016 [63], which regulates the cultural heritage of the autonomous region of Galicia, establishes protection areas of 200 𝑚radius for archaeological sites, where any seabed action is prohibited. Figure 4 shows the different archaeological protected areas of Ribadeo, which are mainly concentrated around the marina harbour with two additional areas located at both sides of the ria mouth, spanning a total surface 32.64 ℎ𝑎 (Table 2). Consequently, the installation of tidal farms in those areas is discarded beforehand, since its operation could disrupt seabed morphology, jeopardising the integrity of archaeological wrecks. 3.3. Biodiversity protected sites Ria de Ribadeo behaves as a positive, partially mixed estuary with a two-layer estuarine circulation pattern [64], which derives from the complex interaction of tides, fresh water run-offs and wind conditions. In addition, from the months of April to October, Ria de Ribadeo experiences coastal upwelling events caused by 8 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 northerly shelf winds. As a result, oceanic water (Eastern North Atlantic Central Water), which is cold and nutrient-rich, enters the ria [65]. The combination of those coastal processes explains the high biological productivity of Ria de Ribadeo [66]. In this context, an abundant population of macro-algae species such as pelvetia canaliculata and ulva is present in the inter-tidal areas of the middle section of the ria (Figure 5). Additional algae species such as ascophyllum nodosum, fucus ceranoides,fucus espirabis,fucus vesiculosus,gracilaria verrucosa and mastocarpus stellatus can also be found in the ria [67]. Therefore, in order to preserve this marine ecosystem, the macro-algae sites (Figure 5) are catalogued as exclusion zones for other maritime activities, covering a surface of 290 ℎ𝑎 (Table 2) 3.4. Fishing and aquaculture sites As mentioned in the previous section, Ria de Ribadeo stands out for its marine biodiversity, laying the foundation for a strong fishing and aquaculture industry. On the one hand, the fishing grounds are mainly located in the ria mouth (Figure 5). On the other hand, shell-fishing gathering (bivalve molluscs and octopuses) represents an important maritime activity both in the middle and inner sections of the ria (Figure 3). Finally, in recent years, the farming of oysters on floating-wooden platforms is increasing significantly, requiring a significant amount of space, especially at the inner ria (Figure 5). Again, in order to avoid potential disruptions to fishing and aquaculture activities, the aforementioned sites are excluded from additional marine uses. 3.5. Touristic sites Touristic and recreational activities are an important source of employment and income generation for the region. In this context, Law 2/2013, which regulates the protection and sustainable use of coastal areas, establishes in its article 69 that bathing or beach areas should cover at least a strip of 200 𝑚width parallel to the coast, in which any other activity is prohibited for safety reasons. 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Figure 4: Archaeological protected areas at Ria de Ribadeo. Figure 5: GIS mapping of exclusive maritime zones at Ria de Ribadeo. Figure 6: Algorithm for the calculation of Dredging Associated Risk (DAR) indicator Figure 7: Spatial distribution of annual operating hours for the Evopod Turbine Figure 8: Spatial distribution of annual energy density for Ria de Ribadeo Figure 9: DAR spatial distribution for Ria de Ribadeo. (a) Uncertainty Level of 10%. (b) Uncertainty Level of 20%. (c) Uncertainty Level of 30%. Figure 10: GIS mapping for tidal farm siting at Ria de Ribadeo Figure 11: DAR levels for potential tidal sites at Ria de Ribadeo 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 4000000 4400000 4800000 500000 750000 1000000 1250000 4819000 4820000 4821000 4822000 4823000 4824000 4825000 656000 657000 658000 659000 660000 661000 662000 IBERIAN PENINSULA GALICIA ASTURIAS Port of Ribadeo x coord, WGS84 UTM 29T (m) Port of Figueras Cantabrian Sea x coord, WGS84 UTM 29T (m) y coord, WGS84 UTM 29T (m) y coord, WGS84 UTM 29T (m) Mediterranean Sea Atlantic Ocean Ria de Ribadeo Figure1 6.58 6.59 6.6 6.61 x 105 4.821 4.822 4.823 4.824 x 106 x coord, WGS84 UTM 29T(m) y coord, WGS84 UTM 29T(m) 100 200 300 400 500 600 700 800 900 1000 C B A kWh/m2 Figure8 6.54 6.56 6.58 6.6 6.62 6.64 x coord, WGS84 UTM 29T(m) 105 4.816 4.818 4.82 4.822 4.824 4.826 4.828 4.83 4.832 y coord, WGS84 UTM 29T(m) 106(a) DAR10% 6.54 6.56 6.58 6.6 6.62 6.64 x coord, WGS84 UTM 29T(m) 105 4.816 4.818 4.82 4.822 4.824 4.826 4.828 4.83 4.832 106(b) DAR20% 6.54 6.56 6.58 6.6 6.62 6.64 x coord, WGS84 UTM 29T(m) 105 4.816 4.818 4.82 4.822 4.824 4.826 4.828 4.83 4.832 106(c) DAR30% 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 DAR Figure9 4821000 4822000 4823000 4824000 658000 659000 660000 x coord, WGS84 UTM 29T(m) Exclusion zone 4 m depth Energy kWh/m² 1000 800 600 400 200 0 Level II areas y coord, WGS84 UTM 29T(m) Figure10 4822500 4823000 4823500 658500 659000 659500 658500 659000 659500 658500 659000 659500 DAR 0.20 0.40 0.60 0.80 Energy KWh/m² 1000 800 600 400 200 0 (a) DAR 10% x coord, WGS84 UTM 29T(m) (b) DAR 20% (c) DAR 30% x coord, WGS84 UTM 29T(m) x coord, WGS84 UTM 29T(m) y coord, WGS84 UTM 29T(m) Figure11 Description Pancha Island Cannon 3 pieces of iron artillery Wreck Illán cove 12 iron cannons with ammunition Valuable ceramic remains Remains of the hull of an unknown wreck. Unidentified wreck Unknown wreck of the 18𝑡ℎ century Lonely cannon Cannon belonging to an unknown wreck Anchor Anchor belonging to an undiscovered wreck Ship Galga Andaluza Spanish pirate ship Ship Corbeta San Francisco Spanish pirate ship Steamship Cabo Torres Merchant ship sunk in 1887 Galeón Santiago de Galicia Ship of the Spanish Navy (XVI century). Considered the best preserved Spanish galleon Table 1: Main characteristics of the archaeological remains found in Ria de Ribadeo Table1 Surface (ℎ𝑎) Archaeological sites 32.64 Fishing and shell-fishing grounds 38.64 Aquaculture sites 30.77 Macro-Algae sites 289.55 Public domain areas 155.04 Beach areas 31.29 Navigation channels 28.43 Table 2: Surface of Maritime exclusive areas Table2 Type Floating Diameter (𝑚) 3 Cut-in velocity (𝑚𝑠−1) 0.7 Cut-off velocity (𝑚𝑠−1) 3.0 Rated velocity (𝑚𝑠−1) 1.9 Rated power (𝑘𝑊) 25 Table 3: Main technical characteristics of the Evopod Turbine Table3 Area A Area B Area C Total Surface (ℎ𝑎) 22.2 8.2 10.9 Usable Surface (ℎ𝑎) 5.6 – 3.4 𝐷 𝐴𝑅10% usable surface (ℎ𝑎) 4.3 – 0.06 𝐷 𝐴𝑅20% usable surface (ℎ𝑎) 4.8 – 1.9 𝐷 𝐴𝑅30% usable surface (ℎ𝑎) 4.9 – 3.4 Table 4: Surface of tidal sites A, B and C Table4