Elsevier Editorial System(tm) for Geomorphology Manuscript Draft Manuscript Number: GEOMOR-1653R2 Title: Morphological characteristics of the Basque continental shelf (Bay of Biscay, northern Spain); their implications for Integrated Coastal Zone Management Article Type: Research Paper Keywords: seafloor cartography, geomorphology, seascape, multibeam echosounder, bathymetric LiDAR, Integrated Coastal Zone Management, Basque shelf Corresponding Author: Mr. Ibon Galparsoro, M.D. Corresponding Author's Institution: First Author: Ibon Galparsoro, M.D. Order of Authors: Ibon Galparsoro, M.D.; Ángel Borja, PhD; Irati Legorburu; Pedro Liria; Carlos Hernández; Guillem Chust, PhD; Adolfo Uriarte, PhD Abstract: This contribution integrates and analyzes data from high-resolution multibeam, seismic profiles, bathymetric LiDAR, and surficial sediment data for the geomorphological seascapes characterisation and process-description of the Basque inner and middle continental shelf (northern Spain). From the data obtained, the Basque shelf is characterised by a heterogeneous seafloor where, on a small spatial scale, different morphologies and sedimentary processes can be observed. Tectonic activity and sea-level changes, together with present processes of sediment supply and climatic conditions, have a critical influence on the present configuration of the continental shelf and the distribution of seafloor types. On the basis of all of the datasets, seafloor classification, bedform analysis, long-term sea-level change-induced seafloor features and anthropogenic features over the seafloor, are described. As a result, three distinct zones have been identified for the Basque shelf, related to the main geomorphological features and seascapes, as summarised below. (i) A western part, with a northwestern orientation, which coincides with the prevailing wave direction. This zone is characterised by a predominantly rocky substrate, except within the mouth of the Nervión estuary, where sandy sediments appear to infill a paleo-channel. (ii) A central part, which is oriented towards the northeast and receives less wave energy. Within this zone, a sedimentary seabed is predominant. Sorted bedforms are well developed and can be detected in water depths in excess of 90 m. (iii) An eastern zone, which is characterised by sedimentary seafloor and shore terraces; here, a flat rocky seafloor is covered by a thin layer of sediments. Throughout the study area, the bathymetry and sedimentary features of the shoreface and inner shelf are controlled mainly by climatic conditions, coastal dynamics and the underlying geological framework. The integration of these data sets, together with their interpretation, is a valuable source of information for Integrated Coastal Zone Management (ICZM) and constitutes a useful tool for implementing various European Directives.

1

Title: Morphological characteristics of the Basque continental shelf (Bay of Biscay, 1

northern Spain); their implications for Integrated Coastal Zone Management 2

3

Authors: Ibon Galparsoro*, Ángel Borja, Irati Legorburu, Carlos Hernández, Guillem 4

Chust, Pedro Liria and Adolfo Uriarte 5

6

Affiliation: AZTI-Tecnalia; Marine Research Division; Herrera Kaia, Portualdea s/n; 7

20110 Pasaia (Spain); *corresponding author‟s e-mail: igalparsoro@azti.es. Tel: +34 8

943004800; Fax: +34 943004801. 9

10

Abstract 11

This contribution integrates and analyzes data from high-resolution multibeam, seismic 12

profiles, bathymetric LiDAR, and surficial sediment data for the geomorphological 13

seascapes characterisation and process-description of the Basque inner and middle 14

continental shelf (northern Spain). From the data obtained, the Basque shelf is 15

characterised by a heterogeneous seafloor where, on a small spatial scale, different 16

morphologies and sedimentary processes can be observed. Tectonic activity and sea-17

level changes, together with present processes of sediment supply and climatic 18

conditions, have a critical influence on the present configuration of the continental shelf 19

and the distribution of seafloor types. On the basis of all of the datasets, seafloor 20

classification, bedform analysis, long-term sea-level change-induced seafloor features 21

and anthropogenic features over the seafloor, are described. As a result, three distinct 22

zones have been identified for the Basque shelf, related to the main geomorphological 23

features and seascapes, as summarised below. (i) A western part, with a northwestern 24

Editor Reviewed ManuscriptClick here to view linked References

2

orientation, which coincides with the prevailing wave direction. This zone is 25

characterised by a predominantly rocky substrate, except within the mouth of the 26

Nervión estuary, where sandy sediments appear to infill a paleo-channel. (ii) A central 27

part, which is oriented towards the northeast and receives less wave energy. Within this 28

zone, a sedimentary seabed is predominant. Sorted bedforms are well developed and can 29

be detected in water depths in excess of 90 m. (iii) An eastern zone, which is 30

characterised by sedimentary seafloor and shore terraces; here, a flat rocky seafloor is 31

covered by a thin layer of sediments. Throughout the study area, the bathymetry and 32

sedimentary features of the shoreface and inner shelf are controlled mainly by climatic 33

conditions, coastal dynamics and the underlying geological framework. The integration 34

of these data sets, together with their interpretation, is a valuable source of information 35

for Integrated Coastal Zone Management (ICZM) and constitutes a useful tool for 36

implementing various European Directives. 37

38

Keywords: seafloor cartography, geomorphology, seascape, multibeam echosounder, 39

bathymetric LiDAR, Integrated Coastal Zone Management, Basque shelf 40

41

3

1. Introduction 42

With the introduction of high-resolution mapping systems, such as the multibeam 43

echosounder (MBES) in the 1990s (Hughes Clarke et al., 1996) or the bathymetric 44

LiDAR (Irish and Lillycrop, 1999; Finkl and Andrews, 2009), new information has 45

been available on seafloor characteristics. The analysis of the MBES data results in the 46

generation of bathymetric models and acoustic backscatter mosaics. Such data can be 47

used to derive the spatial distribution of seafloor relief (with derivatives, such as slope 48

and rugosity), together with bottom type and composition (Fonseca et al., 2009). Such 49

information, in terms of bathymetry, seafloor type distribution and geomorphology, is a 50

valuable source of information for: (i) the description of seabed processes and 51

morphology (Hovland, 2003; Finkl et al., 2008; Hernández-Molina et al., 2008); (ii) 52

habitat mapping (Kostylev et al., 2001; Orpin and Kostylev, 2006; Ryan et al., 2007; 53

Wilson et al., 2007; Brown and Blondel, 2009); (iii) the distribution of benthic 54

biodiversity (Baptist et al., 2006; Thrush et al., 2006; Zajac, 2008); (iv) fish species 55

richness (Pittman et al., 2007); (v) the economic importance of species management 56

(Kostylev et al., 2003; Lucieer and Pederson, 2008; Galparsoro et al., 2009); and, 57

subsequently, (vi) the understanding of benthic ecosystems. Recently, such information 58

has been used for: (i) Integrated Coastal Zone Management (ICZM) (Kostylev et al., 59

2003; Borja et al., 2008b); (ii) the morphological long-term development of dredged 60

material disposal (Cooper et al., 2007; Marsh and Brown, 2009); (iii) the designation 61

and management of marine protected areas (Harris et al., 2008); and (iv) marine spatial 62

planning (Pickrill and Todd, 2003; Campbell and Hewitt, 2006). In particular, new uses 63

of the marine environment (i.e. wind farms, marine protected areas, aquaculture) have 64

triggered a pragmatic approach to the development of marine spatial planning (Douvere 65

and Ehler, 2009). 66

4

The study of the seafloor geomorphology and seascapes, within the Iberian Peninsula, 67

has been undertaken under different perspectives: geological and geomorphological 68

maps of Spain and the continental margin (IGME, 2005); the Prestige oil-spill area 69

(Llave et al., 2008; Vázquez et al., 2008); seascape-shaping mechanisms (Amblas et al., 70

2006); morphosedimentary features (Ercilla et al., 2008); identification of sedimentary 71

features, associated with river discharges (Lobo et al., 2006; Liquete et al., 2007); or 72

rifting (Muñoz et al., 2008). In turn, high quality information on the geology, 73

geomorphology and seafloor characteristics of the southeastern part of the Bay of 74

Biscay (incorporating the Basque continental shelf) is scarce, even absent. Hence, since 75

the first bathymetric charts were produced by the Spanish Marine Hydrographical 76

Institute, in the late 1960´s, only limited research has been undertaken within this 77

region. In the early 1990´s, seafloor characterisation was undertaken to locate and 78

characterise sand banks for beach nourishment purposes (Iberinsa, 1990; 1994). This 79

investigation used side-scan sonar, seismic reflection techniques, surficial grab samples 80

and vibro-core samples. In 2000, in response to an increasing interest in the 81

characterisation of fishing site biotopes, studies were carried out for the Department of 82

Agriculture and Fisheries, of the Basque Government (Galparsoro, 2005). These studies 83

provided an initial approach to seafloor classification, using the Acoustic Seafloor 84

Discrimination System, RoxAnnTM

and side-scan sonar. Other similar studies were 85

carried out, for different purposes, such as: dredged material disposal sites 86

characterisation; urban waste water outfalls inspection; submarine archaeology; and 87

harbour‟s depth of water management. Finally, in 2008, an overall map of the surface 88

sediment distribution of the Basque continental shelf was produced (Jouanneau et al., 89

2008) on the basis of grab sample data. 90

5

Hence, the objectives of the present investigation are: (i) to describe, in an integrative 91

way and at very high-resolution, the main representative geomorphology, seafloor 92

features and submarine seascapes of the Basque continental shelf; and (ii) to infer the 93

processes generating such features. The knowledge generated by this investigation is 94

high quality information to assist in integrated coastal zone management and decision-95

making for different European Directives, such as: ICZM decisions; the Habitats 96

Directive; the Water Framework Directive (WFD, (Borja, 2005); the Marine Strategy 97

Framework Directive (MSFD, (Borja, 2006)); and the NATURA2000 Network. 98

2. Study Area 99

The study area is located on the continental shelf of the Basque Country coast, in the 100

southeastern part of the Bay of Biscay (Fig. 1). The total length of this section of the 101

coast is ca. 150 km. The Cantabrian Sea continental shelf is characterised by its 102

narrowness; in the Basque Country, it ranges from 7 km off Matxitxako Cape, to 20 km 103

off the Oria River estuary (Uriarte, 1998) (Fig. 1). 104

2.1 Geological Framework 105

Tectonic events during the Paleocene and Eocene, together with the Tertiary alpine 106

orogeny, have resulted in deformation of the Cantabrian margin (Ercilla et al., 2008). 107

The entire Basque coastline is located within the Basque Arc domain, including the 108

following regions (or structures), ranging from north to south (Feuillée and Rat, 1971): 109

(i) the monocline of Zumaia, or San Sebastián, which occurs on the Basque coast at 110

Zumaia and extends towards the east; (ii) an anticline to the north of Biscay; (iii) in the 111

western part, the syncline of Bizkaia, which extends along the extensive layer of 112

marbles; and (iv) the anticline of Bilbao (Fig. 1). There are reverse folds and faults (e.g. 113

6

the fault of Bilbao), which form the southern boundary of the Basque Arc (for details, 114

see Fig. 1). 115

Structural features dominate the morphology of the continental shelf. Horsts and 116

anticlines, found generally in Cretaceous rocks, form areas starved of soft Neogene 117

sediments. Faults and synclines, filled with Tertiary materials, underlie sandy 118

depressions (Pascual et al., 2004). The outer section of the continental shelf is a 119

sedimentary Neogene and Pleistocene prism, developed by progradation (Boillot et al., 120

1984). 121

2.2 Oceanographic Setting 122

The maritime climate along the Basque coast is related mainly to its location within the 123

Bay of Biscay and the NE Atlantic (González et al., 2004). In relation to its location and 124

orientation, this part of the coast is exposed to large storms from the NW, produced by 125

evolution of the North Atlantic low pressure systems. Strong NW swell waves dominate 126

and are the most common sea state within the study area. During summer, with the 127

extension of the Azores high pressure system, the North Atlantic low pressure formation 128

sequence slows down, as its intensity lessens. The data used to describe the offshore 129

wave climate affecting the study area have been obtained from the Bilbao offshore buoy 130

(Boya de Bilbao-Vizcaya). On the basis of these data, Liria et al. (2009) summarised the 131

wave climate as described below (see Fig. 1, in Supplementary Material). 132

(i) Summer (June-August): Wave periods of under 10 s over 75% of the time, with 133

representative wave heights of 1.5 m, exceeding 2 m within less than 10% of the 134

measurements. 135

7

(ii) Winter (December-February): High wave periods (i.e. 13 sec), with wave heights 136

greater than 2 m over more than 50% of the time. 137

(iii) Spring and autumn are transitional periods, with intermediate characteristics. 138

(iv) Under extreme offshore wave conditions, significant wave heights can exceed 5 m 139

(several times a year) and, occasionally, 10 m (with return periods of 20 years). 140

The tidal wave is semi-diurnal in character within the Bay of Biscay (Uriarte et al., 141

2004). Along the Basque coast, the mean tidal range is approximately 1.65 m on neap 142

tides and 4.01 m on springs (REDMAR, 2005). Despite the importance of tidally-143

induced surface water fluctuations, the contribution of the tides to the generation of 144

currents is somewhat modest (except within the estuaries) (Uriarte et al., 2004). Away 145

from the estuaries, the tidal currents decrease, with water circulation being governed 146

mainly by wind forcing fluctuations, over a wide range of meteorological frequencies, 147

within the surface and sub-surface waters (Fontán, 2008; Fontán et al., 2009); however, 148

even these are incapable of generating littoral sediment transport along the Basque coast 149

(González et al., 2004). 150

In terms of sediment supply, the Basque Country is drained by 12 main rivers, which 151

discharge 1.57 106

t.yr-1

of suspended material (Uriarte et al., 2004; Ferrer et al., 2009). 152

The geomorphological and hydrological characteristics of the Basque estuarine water 153

bodies are described in Valencia et al. (2004) and Borja et al. (2006). 154

155

156

157

8

3. Material and Methods 158

The data set analysed in the present study was acquired within the framework of a 159

seafloor characterisation and marine habitat mapping programme, which commenced in 160

2004 (Galparsoro et al., 2008a). This investigation integrates different remote sensing 161

techniques, such as MBES (operating from approximately 10 to 100 m water depth), 162

topographic LiDAR (terrestrial land to mid-intertidal zone), bathymetric LiDAR (up to 163

20 m water depth), and aerial photography (Chust et al., 2007; 2008), to cover a 164

continuum from land to deep water environments. At the same time, a Marine 165

Biodiversity Observatory was established by the Basque Government, where 166

sedimentological, pollutant and biological data are collected and integrated into a 167

Marine Spatial Data Infrastructure (Borja et al., 2007; Sagarminaga et al., 2007). 168

3.1. Multibeam Echosounder Bathymetric Data 169

A ship-borne MBES survey was carried out between 2005 and 2008. Bathymetric and 170

seafloor backscatter information were acquired, using high-resolution SeaBat 8125 and 171

SeaBat 7125 MBESs (RESON, 2002, 2006); however, most of the work was carried out 172

using the latest SeaBat 7125 system. The operational frequency of the system was 400 173

kHz, producing 256 beams, in a 128º angle swath with a system depth resolution of 174

0.006 m. The beam width is 0.5º along-track and 1º across-track, producing very small 175

footprints; these, in turn, result in high horizontal resolution Digital Elevation Models 176

(DEM). Incorrect depth values were filtered and tidal correction was applied. As a 177

result, 1 m horizontal resolution DEM was produced. “Snippet” and “pseudo side-scan 178

sonar” non-calibrated backscatter signals were also recorded, together with bathymetric 179

information. Detailed information on the methodology can be found in Borja et al. 180

(2008b) and Galparsoro (2009). Taking into account the limitations of backscatter 181

9

intensity in quantifying and predicting seafloor composition, such a property was used 182

to determine relative differences in seafloor sediment types (Collier and Brown, 2005; 183

Amblas et al., 2006; Brown and Blondel, 2008; Medialdea et al., 2008). Seafloor 184

classification was carried out on the basis of acoustic and morphological facies, together 185

with collated sediment data. „Seafloor-type‟ signatures were extracted, in order to define 186

the seafloor types that could be identified using MBES records. 187

3.2. Topographic and bathymetric LiDAR Elevation Data 188

The digital elevation model used herein was obtained on the basis of a topographic 189

survey of the entire province of Gipuzkoa (1909 km2, in the eastern part of the Basque 190

Country) in 2005 (from January to May) and using Light Detection and Ranging 191

(LiDAR), carried out by the Local Government of Gipuzkoa (Diputación Foral de 192

Gipuzkoa). The sensor was a laser Optech Airborne Laser Terrain Mapper (ALTM) 193

3025, which belongs to the Cartographic Institute of Catalonia (Institut Cartogràfic de 194

Catalunya, ICC); it operates at the infrared wavelength of 1064 nm. The aerial flights 195

were carried out at mid-tide to low-tide (from 0.3 m to 1.6 m below MSL, in Alicante). 196

The 1 m resolution DEM was generated from the LiDAR ground points. It has a vertical 197

accuracy of 0.15 m RMS, in sparsely vegetated and low slope areas. Within this study, a 198

ground (bare-earth) DEM was used, i.e. excluding objects such as buildings, trees, and 199

shrubs. Detailed information on the methodology is described in Chust et al. (2008). 200

On the other hand, very shallow water bathymetric data acquisition was undertaken 201

using the HawkEye MK II airborne bathymetric LiDAR (ALB) system, along the 202

Gipuzkoan coast. This technique consists of two laser scanners: one green (532 nm), 203

used for capturing the bathymetric data; and one red, for the topographic data (1,064 204

nm). The data capture phase was completed in 2008 and 2009; this covered a total 205

10

surface area of 28.3 km2. The flying height for the survey was 400 m, whilst the flight 206

speed was some 150 knots. The pulse repetition rate for the bathymetric LiDAR was 4 207

kHz effective and 1 kHz nominal, allowing for an horizontal spot density of 4 m. 208

Vertical accuracy (i.e. RMSE), compared to known points from the existing survey, was 209

of the order of ±0.25 m. Detailed information on the methodology is described in Costa 210

et al. (2009). 211

3.3. Sub-surface Geological Information 212

Sub-surface geological information was provided on the basis of high-resolution 213

seismic profiles, recorded with a Uniboom system (GeopulseTM

: 200 J, with a shot delay 214

of 500 ms, together with a recording scale of 200 ms). High-frequency filters were 215

applied, within the range of 700-2000 Hz. The surveys were carried out within the 216

mouths of the two major estuaries. In the area of Pasaia, 107 km of profiles were 217

registered, with 150 m distance between the tracks, in April 2007 (Galparsoro et al., 218

2007). A second survey was carried out in the Nervión estuary mouth, in February 219

2008, with 125 km of linear profiles recorded, forming a grid with 250 m spacing 220

(Galparsoro et al., 2008b) (see Fig. 1, for survey locations). 221

3.4. Surficial Sediment Data 222

A total of 2,323 grab samples, corresponding to the period from 1983 up to the present, 223

were collated (Fig. 1), most of them obtained within the marine monitoring network of 224

the Basque Country (see Borja et al., 2004). During this period, sediment analysis was 225

carried out using dry sieving method and Laser Diffraction Particle Size Analyser 226

(LDPSA). In order to homogenise both data sets, a transformation was applied to the 227

results obtained with LDPSA, to refer all data to the results obtained by dry sieving 228

(Rodríguez and Uriarte, 2009). Finally, data were formatted into a GIS format. 229

11

Moreover, 78 new grab samples were collected during the spring of 2009 in those areas 230

where a spatial gap of sedimentological information was identified or in areas where 231

singular morphologies were identified with MBES records and no sedimentologial data 232

were available. Sedimentological data were integrated into the GIS, and a spline-with-233

barriers interpolation algorithm was applied. 234

235

4. Results 236

A 1 m horizontal resolution bathymetric elevation model and seafloor characterisation 237

was obtained, for a total area of 1,096 km2 (Fig. 2a and Supplementary Material from 238

Figs. 2 to 7). The seafloor classification obtained by means of morphology and MEBS 239

backscatter interpretation resulted in: (i) sedimentary seafloor, covering 35% of the 240

surface (Figs. 3a-d), where a sub-classification was undertaken by differentiating 241

between sedimentary cover and sorted bedforms (43 km2 out of the 383 km

2); (ii) mixed 242

rock and sediment seafloor (49% of the total) (Figs. 3e-f and Figs. 4a-b); (iii) rocky 243

seafloor (14% of the total) (Figs. 4c-d); and (iv) areas of dredged material disposal (2% 244

of the total, extending over 23 km2) (Figs. 4e-f); and other singular structures, such as 245

dredging marks and waste water disposal sites (Fig. 5). For details see Table 1 and Fig. 246

2c, for the seafloor classification map. 247

4.1. Morphological Features 248

From the MBES and bathymetric LiDAR data, morphological features have been 249

derived and grouped, taking into account the process that generates them: (i) erosional 250

features; (ii) depositional features; and (iii) anthropogenically-induced structures. 251

252

12

4.1.1. Erosional features 253

4.1.1.1. Rock outcrops 254

Rock seafloor represents 14% of the area surveyed. In the shallow water zone, a 255

continuous belt of rock is present, which is intersected only by sedimentary seafloor off 256

the major estuary mouths. This shallow and highly roughened bedrock is associated 257

with the coastal topography; it presents a slope of approximately 10%, following an 258

inflexion point at 35-40 m water depth (Fig. 2b). In very shallow water, the presence of 259

large rocky blocks is related to coastal cliff erosion (Fig. 4d). The rock strata present 260

different orientations in relation to the coastline. Over the western part, rock strata lie 261

mainly perpendicular to the coastline, producing a low slope seafloor: the presence of 262

coarse sand patches is common between the rock strata. Over the eastern part, the rock 263

strata lie mainly parallel to the coastline, with a high dip generating a rectilinear 264

coastline and the presence of cliffs. Farther offshore, the shelf extends with a milder 265

slope (varying between 1.5% and 2%) and the rock shows lower rugosity. In this zone, 266

the rock outcrop is overlain by a thin veneer of sand cover, but the structural features of 267

the underlying rock are still visible. This seafloor type is complex and patchy, so it has 268

been defined as a mixed bottom type (Fig. 2c and Table 2) here; this covers 49% of the 269

study area. 270

There are several localized zones of rock outcrops. For example, a tower rock has been 271

identified to seaward of Armintza (see Fig. 2c, for location), rising some 40 m above the 272

surrounding seabed and being 130 m in width. 273

274

275

13

4.1.1.2. Shore terraces 276

Eight shoreline terraces have been identified on the rocky seafloor, corresponding to 277

periods of sea-level still-stand, at approx.: -37 m, -52 m, -56 m, -70 m, -73 m, -75 m, -278

87 m and -92 m water depth (relative to the Local Datum, which is 2.016 m above 279

Spring Low Tide level). The shallower terrace is the steepest and longest and extends 280

continuously along the inner continental shelf (Fig. 4c). Above this water level, the 281

rocky seafloor is very rough and constitutes the shallow rock belt (as described 282

previously). Shore terraces located deeper are less steep and the rocky seafloor is more 283

flat, in response to erosion at still-stand periods (Fig. 6). 284

4.1.1.3. Paleo-river channels 285

The rocky seafloor shows numerous incisions, of various sizes, that correspond to 286

paleo-river channels. The channels are oriented generally shore-normal and are most 287

likely associated with geomorphological features of the modern shoreline. More than 40 288

paleo-channels have been identified within the study area (Fig. 2c). The paleo-channels 289

do not contain any tributaries; they are very sinuous (the sinuosity index of the channels 290

lay between 0.8 and 0.9), with a S-N orientation; some of them incise across the entire 291

width of the rocky shelf, up to a water depth of 85 m. The largest paleo-river channels 292

represent the offshore continuity of the present estuaries, within the sub-tidal area, being 293

200 m wide and 5 km long. The paleo-river channels are bifurcated, indicating different 294

routes corresponding to different periods; at present, most of them are covered partially 295

by recent sediments. 296

297

298

14

4.1.2. Depositional features 299

The sedimentary seafloor covers 35% of the total surface area. The predominant grain 300

size was classified as fine sand (median 2.1 Phi), whilst the mean composition of all of 301

the samples was: 75% sand, 18% mud and 4% gravel (Fig. 7). The mean organic matter 302

content was 4.1%, 161 mV for redox potential and 35% CO3 content. The mean grain 303

size was 2.2 Phi over the western part of the continental shelf, 2.3 Phi over the middle 304

part, and 2.0 Phi over the eastern part. 305

4.1.2.1. Infra-littoral Prograding Wedge 306

Infra-littoral Prograding Wedges (IPW) are present, associated with the mouths of major 307

rivers. The IPW forms a low-angle slope (0.6º on average), which represents the infra-308

littoral prograding environment, extending to a strong break in slope at water depths of 309

30-35 m. This water depth corresponds to the mean level of the storm wave base. To 310

seaward of this break point, a slope (2.10º to 4.4º, depending upon the wedge front 311

compared with the wave fetch) extends to 40-50 m water depth. Even farther to 312

seaward, a decrease in the angle of the slope characterises the slope toe, evolving 313

seawards to the inner continental shelf. 314

The seismic profiles recorded indicate different deposits of material; amongst these, the 315

IPW could be identified as a veneer of Holocene deposits, overlying the coarse-grained 316

deposits (Fig. 8). The layer shows low reflectivity and homogeneous material 317

composition. The maximum width observed for this layer was 9 m, at a 30-35 m water 318

depth, near Bilbao; it was observed also that this layer becomes thicker, to seawards. 319

320

321

15

4.1.2.2. Sorted bedforms 322

These structures are present as slightly depressed, elongate features, which lie 323

perpendicular to the isobaths (Figs. 2c, 3a, 3b, 9). The DEM aspect indicates that the 324

seafloor surface on the sorted bedforms is oriented mainly towards the north; 325

meanwhile, the surrounding sedimentary seafloor is oriented to the northwest, as a 326

response to sediment remobilisation by wave action. The sorted bedforms are up to 0.5 327

m in depth, relative to the surrounding upper shoreface. Most of the bedforms develop 328

just outside the fair-weather surf zone water depth (20-25 m), up to water depths of 90-329

100 m. The largest of the bedforms are around 1,650 m in width and 4,400 m in length 330

(Figs. 2c, 9). The longitudinal axis is predominantly NE-oriented (22º to 53º) (Table 2). 331

In terms of the relative direction between the swell wave front (equivalent to storm 332

waves) and the sorted bedform axis direction, the angles range between 101º and 157º. 333

Meanwhile, the angle between the axis of the sorted bedforms and the coastline 334

orientation ranges between 71º and 127º. Sorted bedforms of different shapes have been 335

identified, distributed within various parts of the study area (Fig. 9). 336

Within the sorted bedform areas, megaripples have been identified; these are long, 337

straight-crested and symmetrical (wavelength = 0.7-1.2 m; height = 0.1-0.25 m). The 338

crests appear to be well developed, maintaining continuity over some tens of metres. 339

The megaripples present low undulations, with occasional bifurcation, inferring their 340

wave-induced origin. The crests are oriented mainly in a SW-NE direction, in 341

accordance with the direction which lies perpendicular to the predominant waves (Figs. 342

3a, 3b). 343

The grab samples showed a coarser composition and 38.8% CO3, which is higher than 344

surrounding material, producing higher MBES backscatter response. Samples collected 345

16

from the bedform areas showed a mean grain size of 1.25 Phi, 80.3% of sand, 11.7% of 346

gravel and shell debris, 7.7% of mud, and 3.2% of organic matter. Video records have 347

indicated that the boundary is sharp between the surrounding fine sand and coarse sand, 348

inside the bedform area. 349

4.1.2.3. Morphologic Wave Closure Depth 350

The water depth limit of significant wave energy levels interacting with a sand bed was 351

determined and mapped, by means of wave-induced seafloor morphology and 352

bathymetric irregularities identification and interpretation (Fig. 2c). A mean water depth 353

value was found to be 19.8±4.4 m (relative to the Alicante Mean Sea Level). Wave 354

closure depth was dependant upon coastline orientation to wave fetch and surrounding 355

rock outcrop configuration because the beaches are “pocket type”. 356

4.1.2.4. Rhythmic Surf zone Sandbars and Troughs 357

Longshore bars are identified in the bathymetric LiDAR data as crescentic bars (quarter-358

moon type patterns, with the horns of the moon facing shorewards), as a result of the 359

interaction with an alongshore rhythmic circulatory pattern. Water depths vary between 360

2 and 4 m and the bars occur from 230 to 250 m from the shoreline; they range in width 361

from 150 to 230 m. Bar crests in many of the locations follow the 4 m isobath (referred 362

to Local Datum). It has been observed that single to double longshore bars (Fig. 10), 363

together with troughs associated with the bars, originate as 1.5 m depressions. 364

365

366

367

17

4.1.3. Antropogenic structures 368

Several artificial structures have been mapped and characterised: (2) gas pipelines; an 369

aquaculture water pumping pipeline; (8) dredged material disposal areas (Figs. 4e, 4f); 370

suction dredging marks (Figs. 5a, 5b); (2) sewage outfalls (Figs. 5c, 5d); and numerous 371

shipwrecks. 372

Of the above, in terms of morphology and surface area, the dredged material disposal 373

areas are the largest anthropogenic seabed alterations. The disposal areas are easily 374

recognisable on the sedimentary seafloor, lying close to the most important harbours, in 375

terms of maritime traffic and dredging activity (e.g. Pasaia and Bilbao). In some areas, 376

the disposed material completely covers the seafloor, but the settled disposals show 377

distinctive “ring-like” structures (Fig. 4e, 4f). These features are usually around 40 m in 378

diameter and 0.5 m in height, in relation to the surrounding seafloor. The backscatter 379

indicates that such dredged material disposal areas are characterised by a very 380

heterogeneous seafloor, where very coarse-grained material is mixed with fine 381

sediments. In contrast, seismic profiles show that this disposed material is located 382

within the surficial part of the sand bank. 383

5. Discussion 384

5.1. Sectors 385

On the basis of the main geomorphological and morphosedimentary features mentioned 386

in the previous section, three sectors have been identified within the Basque continental 387

shelf (Fig. 2c), as described below. 388

(i) Over its western part, the coast has a northwestern orientation, which coincides 389

with the prevailing wave direction. Major faults and rock strata are NW–390

18

oriented, having a smooth slope (Fig. 2b). This sector is characterised by 391

predominantly rocky substrate (over 80% of the area) (Table 1), except at the 392

mouth of the Nervión estuary, where sandy sediments infill the paleo-channel 393

with thicknesses of > 20 m. 394

(ii) The middle part of the continental shelf receives relatively less wave energy than 395

the sector described previously, due to the coastal orientation towards the wave 396

energy direction. Sedimentary deposits cover 35% of the seabed surface and 397

morphosedimentary bedforms are common features over this sector (Table 1). 398

(iii) Within the eastern sector, sedimentary seafloor cover represents 54% of the 399

surface (Table 1). The rocky seafloor is characterised by tectonically-produced 400

morphologies, paleo-channel incisions and various well-developed shore 401

terraces. Rock strata lie parallel to the coastline and perpendicular to the 402

prevailing wave direction. A shallow and very rough rock belt is identifiable 403

along the coastline. 404

The seascapes described for the Basque continental shelf are the result of a combination 405

of processes, at different temporal and spatial scales. The major mechanisms controlling 406

the seascape shaping are deemed to be: (i) the present prevailing wave energy climate; 407

(ii) variations in sea-level, as a response to global eustatic changes; and (iii) local 408

subsidence and uplift of the continental margin, due to tectonic activity, related to plate 409

movements (Klingebiel and Gayet, 1995). Such neotectonic uplift movements have 410

been used to explain aspects of the evolution of the southern Bay of Biscay margin 411

during the Neogene and Pleistocene (Mary, 1983); they are responsible for the present 412

morphology of the continental shelf. Moreover, coastal rock lithologies (mainly 413

sandstone, calcareous sandstone, limestone, clay, limonites and marls and marly 414

19

limestones (EVE, 2003)), have permitted the rapid erosion of the rocky substrate during 415

sea-level change, throughout the Quaternary; consequently, the development of the 416

presently identifiable seascapes. 417

5.2. Seascapes on the Continental Shelf 418

The disposition of the sedimentary rock strata is an important factor controlling the 419

coastal and shelf configuration: (i) when the direction of the strata lies perpendicular to 420

the coastline, the formation of embayments is enhanced and a smooth slope shelf is 421

present, as described for the western zone; and (ii) when it lies parallel to the cliff front, 422

the coastline is rectilinear in shape, with well-developed abrasion platforms (Portero et 423

al., 1991) and a high gradient to seawards, as in the eastern zone. The inner shelf, up to 424

35-40 m water depth, is covered by an almost continuous belt of rocks, which 425

constitutes an extension of the rocks of the adjacent continental cliffs (Pascual et al., 426

2004). This rock belt has been identified along almost all of the continental shelf, 427

showing steep slope and high rugosity, which indicates a rapid phase of sea-level rise 428

(Fig. 11); this could correspond to the Younger Dryas period. This terrace has been 429

identified throughout almost all of the continental shelf. 430

The continental shelf is a sedimentary Neogene and Pleistocene prism, developed by 431

progradation (Boillot et al., 1984). The shelf is covered by sandy sediments; these, in 432

turn, isolate the exposed rocky areas of the seabed (Rey and Sanz, 1982). Ten major 433

sandbanks have been identified, which represent the extension of the present estuaries 434

(Fig. 2c) and have been identified as Infra-littoral Prografing Wedge (IPW). These types 435

of structures have been described for other parts of the Spanish Atlantic coast by 436

Hernández-Molina (2000). In all cases, a sedimentary deposit of high reflectance has 437

been identified at the base of the IPW, which has been characterised using sediment 438

20

core data. This deposit could correspond to a reworked transgressive gravel layer, which 439

separates this unit from Holocene marine sands. As stated by Cirac et al., (2000), since 440

ca. 4,000 years BP, sea-level has remained approximately constant and reworking has 441

affected mainly the upper 1–2 m of sediment on the inner shelf. However, as described 442

by Jouanneau et al. (2008), on the eastern part of the Basque coast, the middle and outer 443

shelves are covered by an extended shelf mud patch. This fine sedimentary unit is 444

bounded by rocky outcrops in a shoreward direction and, after Jouanneau et al. (2008), 445

the deeper and northward extent of the mud patch is indistinct, having no fixed 446

boundary. 447

On the other hand, coarse-grained sand patches have been identified, arranged in strips 448

and furrows (Fig. 2c). These features have been identified as rippled scour depressions, 449

or sorted bedforms as observed elsewhere (Cacchione et al., 1984; Thieler et al., 1995; 450

Ferrini and Flood, 2005; Diesing et al., 2006; Lo Iacono and Guillén, 2008). As 451

commented upon above, these bedforms are present as slightly depressed, elongate 452

features, consisting of gravelly and sandy gravel sediments; these form, usually, ripples 453

and dunes lying adjacent to medium to fine sand bodies (Figs. 3a-3b) (Murray and 454

Thieler, 2004; Gutierrez et al., 2005). For the Basque continental shelf, bottom stresses 455

related to wave-induced currents are probably the major component contributing to the 456

resuspension of sediment, together with the genesis of such morphosedimentary 457

structures. The principal evidence applied to this hypothesis is that they are present at 458

water depths which are deeper than the storm wave base. Previous studies undertaken 459

on the effect of tidal currents and waves upon the sediments of the French continental 460

shelf of the Bay of Biscay have confirmed that the prevailing wave climate is the 461

predominant agent affecting sediment dynamics; this is not only to areas lying adjacent 462

to the coastline but extends also to the continental shelf break (Barthe and Castaing, 463

21

1989). It has been observed that the direction of the longitudinal axis of the sorted 464

bedformswithin the coastal sectors facing the storm wave direction, lies nearly 465

perpendicular to the wave direction. Meanwhile, the coastal sectors that do not face the 466

prevailing storm wave direction show a higher angle between the wave and the sorted 467

bedform longitudinal axis directions (for details, see Table 2). Thus, it may be 468

concluded that the shape and direction of the sorted bedform is a combination of the 469

factors in which the storm wave direction and coastal orientation to the waves play a 470

major controlling role. Current measurements are required in order to analyse the role of 471

tidal currents in maintaining such features, as proposed by Diesing et al., (2006). The 472

measurement of currents during storm events and calm periods (to identify other types 473

of currents) and hydrodynamic modelling, together with an applied shear stress analysis 474

for the sediments, could explain the origin of the sorted bedforms of the Basque 475

continental shelf. On the other hand, gravel material identified in the sorted bedforms 476

could be explained as being outcropping material of a buried sediment layer lying 477

beneath the Holocene sands (as described by Browder and McNinch (2006)); this has 478

been identified in the seismic profiles from the study area. In water depths of 20–30 m 479

below present sealevel, present-day reworking appears to be limited to the upper tens of 480

centimetres of sediments, and mainly during major storms. Winnowing of Pleistocene 481

coarse-grained sediments, as well as of transgressive sand patches, provides the material 482

for this thin uppermost highstand deposit, still in equilibrium with contemporary 483

processes (Cirac et al., 2000). 484

Sorted bedforms are interesting features that connect very shallow water processes to 485

deeper water canyons; as such, they might be considered the initial part of more 486

complex structures present in deeper waters. Such features are the main pathways 487

through which shelf sediments are transported, in the form of sediment gravity flows, 488

22

into the abyssal plains; their geomorphology has been largely ignored, due mainly to 489

their complex terrain and the difficulty in studying the seafloor (Lastras et al., 2009). 490

In terms of artificial structures, dredged material disposal sites have been identified as 491

one of the most significant changes to the present seascape of the Basque continental 492

shelf, in terms of surface area. The origin of this disposed material is mainly from the 493

maintenance dredging of the harbours, during the last 100 years (Uriarte et al., 2004), 494

together with blast furnace slag disposal (Borja et al., 2008b) and material derived from 495

mining draining into the ports. Backscatter signals indicate that the deposited material is 496

composed of material coarser than the surrounding sediments. The majority of the 497

dredged material disposal sites have not been characterised, up until the present time; as 498

such, their extent and distribution have been essentially unknown. The distinctive `ring-499

like´ structures of these sediments reflect the transfer of vertical, into horizontal, 500

momentum when the disposal hits the seabed (Stockmann et al., 2009). It could be 501

inferred that the applied shear stress was insufficiently high to enhance erosional 502

processes of the coarser material. If the coarser sediments overlie the finer ones (as 503

could be seen also in the seismic profile), i.e. armouring, the lower layer deposit is no 504

longer susceptible to wave action. Even if marine sand extraction is very limited in 505

Spain, such material disposal sites reduce the availability of such sediment resources for 506

beach nourishment. Dumping areas should be monitored during future surveys, with 507

repetition sampling intervals of several years, as the observed processes occur slowly 508

(Stockmann et al., 2009). 509

510

511

23

5.3. Geomorphology as a source of information for Integrated Coastal Zone 512

Management 513

In recent years, much world-wide legislation has focused upon the protection and/or 514

restoration seas, by ensuring that human activities are carried out in a sustainable 515

manner, to provide safe, clean, healthy and productive marine waters (Borja et al., 516

2008a). As an example, in Europe, much legislation (e.g. ICZM, Habitats Directive, 517

WFD, and MSFD (European Commission, 2008) attempts to promote the sustainable 518

use of the seas and the conservation of marine ecosystems. The final objective of these 519

policies is to maintain a good environmental or ecological status for marine waters, 520

habitats and resources. The concept of environmental status takes into account the 521

structure, function and processes of marine ecosystems, bringing together physical, 522

chemical, physiographic, geographic and climatic factors; subsequently, integrating 523

such interactions, with anthropogenic impacts and activities undertaken in the area 524

concerned (Borja et al., 2008a). 525

Within this context, the mapping of geomorphological features within a regional sea is 526

highly relevant for ICZM. Hence, Borja and Collins (2009) have highlighted some 527

weaknesses in the present research undertaken within the Bay of Biscay, proposing a 528

future research agenda. Amongst the different research priorities, these authors remark 529

that although much effort has been devoted to the study of the geology and 530

sedimentology of this area, only limited knowledge is available for the continental shelf 531

and slope. Moreover, they call for a general definition and mapping of benthic and 532

pelagic habitats within the Bay of Biscay as being required for any further management 533

and spatial planning of this particular regional sea (Douvere and Ehler, 2009). 534

Hence, the information obtained from the geomorphological mapping presented in this 535

24

contribution can be (or is being) used for a variety of investigations, which converge 536

finally into an integrated management of this coastal region: (i) marine spatial planning, 537

including wave energy modelling, for renewable energy exploitation (see Galparsoro et 538

al., 2008c); (ii) essential fish habitat and economically-important species habitat 539

suitability, for fishing resources (Galparsoro et al., 2009); (iii) dredged sediment 540

disposal management; (iv) offshore aquaculture; (v) Marine Protected Areas and 541

biodiversity conservation (Castro et al., 2004); (vi) habitat mapping (Chust et al., 2007; 542

2008); (vii) ecosystem goods and services valuation; (viii) biological quality index 543

development, for large spatial scale application (Borja and Dauer, 2008); (ix) land-sea 544

exchange modelisation (Ferrer et al., 2009; Fontán et al., 2009); (x) the integration of 545

such information for environmental status assessment (Borja et al., 2009); and (xi) 546

human activity sensitivity maps. 547

Moreover, the three physiographic units identified here are coincident with the three 548

main water bodies identified in the Basque Country for ecological status assessment 549

within the WFD (Borja et al., 2004; 2006). Differences in grain size, between the units, 550

show slight differences in the depositional pattern, due probably to differences in wave 551

energy; this leads ultimately to differential transport within each of the units (Ferrer et 552

al., 2009). 553

Hence, Maritime Spatial Planning (MSP), which incorporates all the concepts and 554

investigations commented upon above, is an important tool for the development of an 555

integrated maritime policy in Europe (European Commission, 2008). Some of the key 556

principles of this MSP require strong basic scientific knowledge, applicable to the 557

different European directives, which are being or are to be implemented in the near 558

future. It is within this context that information on the geomorphology is a first-step in 559

25

an improved knowledge of habitats, uses, goods and services, and the ecosystem-based 560

management of marine waters (Borja et al., 2008a; Douvere and Ehler, 2009). 561

562

6. Conclusions 563

In this investigation, the latest high-resolution remote sensing and sediment sampling 564

techniques have been used and integrated for the Basque coastal, inner and middle 565

continental shelf mapping and seafloor characterisation. It has been observed that the 566

Basque continental shelf is characterised by a heterogeneous seafloor where, over a 567

relatively small spatial scale, diverse seascapes are present and have originated from the 568

interaction of different processes. It may be concluded that tectonic activity, basement 569

topography and sea-level changes, together with processes of sediment supply and 570

prevailing climatic conditions, have a critical influence on the configuration of the 571

continental shelf seascapes and the distribution of seafloor material. Tectonic activity 572

and erosional processes formed the present rock seafloor and shape, where more than 40 573

paleo-river channels and 9 shore terraces have been identified. In terms of depositional 574

features, IPW and sorted beforms are common features of the continental shelf. In terms 575

of anthropogenic structures, sediment disposal is the main seafloor alteration in the 576

study area. Here is the first detailed characterisation of the seascapes and morphologies 577

of the Basque inner and middle continental shelf, together with an initial description of 578

marine processes interacting upon the seafloor. The background scientific knowledge 579

produced in this investigation, together with the cartographic information generated, is 580

being used for the implementation of several European Directives; these are, ultimately, 581

needed for an effective ICZM and MSP. 582

583

26

Acknowledgments 584

This project was supported by the Department of Environment, Land Use, Agriculture 585

and Fisheries, of the Basque Government. The authors would like to thank: the Bilbao 586

and Pasaia Port Authorities, for the geophysical studies; PhD, Javier Hernández-Molina 587

(University of Vigo), for his useful comments to the manuscript; and Mikelo Elorza 588

(Diputación Foral de Gipuzkoa) and Blom Aerofilms for the technical support in 589

analysis of the topographic LiDAR and bathymetric LiDAR data. 590

Irati Legorburu was funded by the Fundación Centros Tecnológicos, with a Training, 591

Specialization and Technological Development grant. We wish to thank: Professor 592

Michael Collins (School of Ocean and Earth Science, University of Southampton (UK) 593

and AZTI-Tecnalia (Spain)) for kindly advising on some details of the manuscript; 594

likewise colleagues of AZTI-Tecnalia, especially Jon Berregi and Luis Cuesta, who 595

collaborated in the acquisition and processing of the MBES data. This paper is 596

contribution number 477 from AZTI-Tecnalia (Marine Research Division). 597

598

References 599

600

Amblas, D., Canals M., Urgeles R., Lastras G., Liquete C., Hughes-Clarke J. E., 601

Casamor J. L., Calafat A. M., 2006. Morphogenetic mesoscale analysis of the 602

northeastern Iberian margin, NW Mediterranean Basin. Marine Geology, 234, 3-20. 603

Baptist, M. J., van Dalfsen J., Weber A., Passchier S., van Heteren S., 2006. The 604

distribution of macrozoobenthos in the southern North Sea in relation to meso-scale 605

bedforms. Estuarine, Coastal and Shelf Science, 68, 538-546. 606

Barthe, X., Castaing P., 1989. Étude théorique de l‟action des courants de marée et des 607

houles sur les sédiments du plateau continental du Golfe de Gascogne. 608

Oceanologica Acta, 12, 325-334 (in French). 609

Boillot, G., Montadert L., Lemoine M., Biju-Duval B. (Eds.), 1984. Les marges 610

continentales actuelles et fossiles autour de la France. Paris. 342 pp. (in French). 611

27

Borja, Á., Franco J., Valencia V., Bald J., Muxika I., Belzunce M. J., Solaun O., 2004. 612

Implementation of the European water framework directive from the Basque 613

country (northern Spain): a methodological approach. Marine Pollution Bulletin, 48, 614

209-218. 615

Borja, Á. 2005. The European water framework directive: A challenge for nearshore, 616

coastal and continental shelf research. Continental Shelf Research, 25, 1768-1783. 617

Borja, Á. 2006. The new European Marine Strategy Directive: Difficulties, 618

opportunities, and challenges. Marine Pollution Bulletin, 52, 239-242. 619

Borja, Á., Galparsoro I., Solaun O., Muxika I., Tello E. M., Uriarte A., Valencia V., 620

2006. The European Water Framework Directive and the DPSIR, a methodological 621

approach to assess the risk of failing to achieve good ecological status. Estuarine, 622

Coastal and Shelf Science, 66, 84-96. 623

Borja, Á., Galparsoro I., Sagarmínaga Y., 2007. Observatorio de la Biodiversidad del 624

Medio Marino de la Costa Vasca: bienes y servicios proporcionados por la 625

biodiversidad marina. Informe inédito de la Fundación AZTI-Tecnalia para la 626

Dirección de Biodiversidad del Departamento de Medio Ambiente y Ordenación del 627

Territorio del Gobierno Vasco. 61 pp. (in Spanish). 628

Borja, Á., Dauer D. M., 2008. Assessing the environmental quality status in estuarine 629

and coastal systems: Comparing methodologies and indices. Ecological Indicators, 630

8, 331-337. 631

Borja, Á., Bricker S. B., Dauer D. M., Demetriades N. T., Ferreira J. G., Forbes A. T., 632

Hutchings P., Jia X., Kenchington R., Marques J. C., Zhu C., 2008a. Overview of 633

integrative tools and methods in assessing ecological integrity in estuarine and 634

coastal systems worldwide. Marine Pollution Bulletin, 56, 1519-1537. 635

Borja, Á., Tueros I., Belzunce M. J., Galparsoro I., Garmendia J. M., Revilla M., Solaun 636

O., Valencia V., 2008b. Investigative monitoring within the European Water 637

Framework Directive: a coastal blast furnace slag disposal, as an example. Journal 638

of Environmental Monitoring, 10, 453-462. 639

Borja, Á., Collins M., 2009. Regional Seas integrative studies, as a basis for an 640

ecosystem-based approach to management: The case of the Bay of Biscay. 641

Continental Shelf Research, 29, 951-956. 642

Borja, Á., Bald J., Franco J., Larreta J., Muxika I., Revilla M., Rodríguez J. G., Solaun 643

O., Uriarte A., Valencia V., 2009. Using multiple ecosystem components, in 644

assessing ecological status in Spanish (Basque Country) Atlantic marine waters. 645

Marine Pollution Bulletin, 59, 54-64. 646

Boya de Bilbao-Vizcaya, Longitud -3.052E; Latitud 43.640N; Profundidad 600 m. 647

Banco de Datos Oceanográficos de Puertos del Estado (www.puertos.es). Ministerio 648

de Fomento del Gobierno de España (in Spanish). 649

Browder, A. G., McNinch J. E., 2006. Linking framework geology and nearshore 650

morphology: Correlation of paleo-channels with shore-oblique sandbars and gravel 651

outcrops. Marine Geology, 231, 141-162. 652

Brown, C. J., P. Blondel, 2009. Developments in the application of multibeam sonar 653

backscatter for seafloor habitat mapping. Applied Acoustics, 70, 1242-1247. 654

28

Cacchione, D. A., Drake D. E., Grant W. D., Tate G. B., 1984. Rippled scour 655

depressions on the inner continental shelf of central California. Journal of 656

Sedimentary Petrology, 54, 1280-1291. 657

Campbell, M. L., Hewitt C. L., 2006. A hierarchical framework to aid biodiversity 658

assessment for coastal zone management and marine protected area selection. Ocean 659

& Coastal Management, 49, 133-146. 660

Castro, R., Uriarte, A. Martínez de Murguía A., Borja Á., 2004. Biodiversity and 661

conservation of wildlife and natural habitats. Elsevier Oceanography Series. 662

Oceanography and Marine Environment of the Basque Country. Á. Borja and M. 663

Collins (Eds.). Elsevier. 70, pp. 531-547. 664

Chust, G., Galparsoro I., Borja Á., Franco J., Beltrán B., Uriarte A., 2007. Detección de 665

cambios recientes en la costa vasca mediante ortofotografía. Lurralde, 30, 59-72 (in 666

Spanish). 667

Chust, G., Galparsoro I., Borja Á., Franco J., Uriarte A., 2008. Coastal and estuarine 668

habitat mapping, using LIDAR height and intensity and multi-spectral imagery. 669

Estuarine, Coastal and Shelf Science, 78, 633-643. 670

Cirac, P., Berne S., Castaing P., Weber O., 2000. Processus de mise en place et 671

d'évolution de la couverture sédimentaire superficielle de la plate-forme nord-672

aquitaine. Oceanologica Acta, 23, 663-686 (in French). 673

Collier, J. S., Brown C. J., 2005. Correlation of sidescan backscatter with grain size 674

distribution of surficial seabed sediments. Marine Geology, 214, 431-449. 675

Cooper, K., Boyd S., Eggleton J., Limpenny D., Rees H., Vanstaen K., 2007. Recovery 676

of the seabed following marine aggregate dredging on the Hastings Shingle Bank 677

off the southeast coast of England. Estuarine, Coastal and Shelf Science, 75, 547-678

558. 679

Costa, B. M., Battista T. A., Pittman S. J., 2009. Comparative evaluation of airborne 680

LiDAR and ship-based multibeam SoNAR bathymetry and intensity for mapping 681

coral reef ecosystems. Remote Sensing of Environment, 113, 1082-1100. 682

Diesing, M., Kubicki A., Winter C., Schwarzer K., 2006. Decadal scale stability of 683

sorted bedforms, German Bight, southeastern North Sea. Continental Shelf 684

Research, 26, 902-916. 685

Douvere, F., Ehler C. N., 2009. New perspectives on sea use management: Initial 686

findings from European experience with marine spatial planning. Journal of 687

Environmental Management, 90, 77-88. 688

Ercilla, G., Casas D., Estrada F., Vazquez J. T., Iglesias J., Garcia M., Gomez M., 689

Acosta J., Gallart J., Maestro-González A., 2008. Morphosedimentary features and 690

recent depositional architectural model of the Cantabrian continental margin. Marine 691

Geology, 247, 61-83. 692

European Commission, 2008. Communication from the Commission: Roadmap for 693

Maritime Spatial Planning: Achieving Common Principles in the EU. Commission 694

of the European Communities. Brussels. 12 pp. 695

EVE, 2003. Mapa geológico del País Vasco. Mapa, memoria y bases de datos. Escala 696

1/25.000. Ente Vasco de la Energía. ISBN: 84-8129-054-8 (in Spanish). 697

29

Ferrer, L., Fontán A., Mader J., Chust G., González M., Valencia V., Uriarte Ad., 698

Collins M. B., 2009. Low-salinity plumes in the oceanic region of the Basque 699

Country. Continental Shelf Research, 29, 970-984. 700

Ferrini, V. L., Flood R. D., 2005. A comparison of Rippled Scour Depressions 701

identified with multibeam sonar: Evidence of sediment transport in inner shelf 702

environments. Continental Shelf Research, 25, 1979-1995. 703

Feuillée, P., Rat P., 1971. Structures et paléogéographies Pyrénéo-Cantabriques. 704

Historie Structurale du Golfe de Gascogne. Publications de l‟Institut Français du 705

pétrole, Paris, pp. 1-48 (in French). 706

Finkl, C. W., Becerra J. E., Achatz V., Andrews J. L., 2008. Geomorphological 707

Mapping along the Upper Southeast Florida Atlantic Continental Platform; I: 708

Mapping Units, Symbolization and Geographic Information System Presentation of 709

Interpreted Seafloor Topography. Journal of Coastal Research, 24, 1388-1417. 710

Finkl, C. W., Andrews J. L., 2009. Shelf Geomorphology along the Southeast Florida 711

Atlantic Continental Platform: Interpretation of Airborne Laser Bathymetry. Journal 712

of Coastal Research, 2, 1494-1498. 713

Fonseca, L., Brown C., Calder B., Mayer L., Rzhanov Y., 2009. Angular range analysis 714

of acoustic themes from Stanton Banks Ireland: A link between visual interpretation 715

and multibeam echosounder angular signatures. Applied Acoustics, 70, 1298-1304. 716

Fontán, A., 2008. Physical processes governing water circulation in the southeastern 717

limit of the Bay of Biscay. University of Southampton, MPhil thesis in Physical 718

Oceanography, 136 pp. 719

Fontán, A., González M., Wells N., Collins M., Mader J., Ferrer L., Esnaola G., Uriarte 720

A., 2009. Tidal and wind-induced circulation within the Southeastern limit of the 721

Bay of Biscay: Pasaia Bay, Basque Coast. Continental Shelf Research, 29, 998-722

1007. 723

Galparsoro, I., 2005. Elaboración de una cartografía sedimentológica detallada y de 724

mapas de biotopos marinos del litoral vasco. Informe inédito de AZTI-Tecnalia para 725

la Viceconsejería de Desarrollo Agrario y Pesquero, Departamento de Agricultura, 726

Pesca y Alimentación, Gobierno Vasco. 28 pp (in Spanish). 727

Galparsoro, I., Hernández C., Rodríguez J. G., Liria P., Fontán A., González M., Uriarte 728

A., 2007. Trabajos de caracterización y medición de la arena existente en la 729

plataforma marina costera junto al monte Jaizkibel al este de la bocana de acceso al 730

puerto de Pasajes. Informe inédito elaborado por AZTI-Tecnalia para la Autoridad 731

Portuaria de Pasajes. 89 pp. + anexos. (in Spanish). 732

Galparsoro, I., Chust G., Hernández C., Borja Á., del Campo A., Uriarte A., 2008a. 733

Seafloor cartography and habitat mapping of the Basque inner continental shelf. XI 734

International Symposium on Oceanography of the Bay of Biscay. Unidad de 735

Investigación Marina de Tecnalia, Pasaia, pp. 102-103. 736

Galparsoro, I., Hernández C., Uriarte A., 2008b. Campaña de prospección geofísica en 737

la Zona II de la Autoridad Portuaria de Bilbao. Informe inédito elaborado por AZTI-738

Tecnalia para la Autoridad Portuaria de Bilbao. AZTI-Tecnalia. 33 pp (in Spanish). 739

Galparsoro, I., Liria P., Legorburu I., Ruiz-Minguela P., Pérez P., Marqués J., Torre-740

Enciso Y., González M., 2008c. Atlas de energía del oleaje. La planificación 741

30

espacial marina como herramienta en la selección de adecuadas para la instalación 742

de captadores. Revista de Investigación Marina, 8, 1-9 (in Spanish). 743

Galparsoro, I., Borja Á., Bald J., Liria P., Chust G., 2009. Predicting suitable habitat for 744

the European lobster (Homarus gammarus), on the Basque continental shelf (Bay of 745

Biscay), using Ecological-Niche Factor Analysis. Ecological Modelling, 220, 556-746

567. 747

González, M., Uriarte A., Fontán A., Mader J., Gyssels P., 2004. Chapter 6 Marine 748

Dynamics. Elsevier Oceanography Series. Oceanography and Marine Environment 749

of the Basque Country. Á. Borja and M. Collins (Eds.). Elsevier, pp. 133-157. 750

Gutierrez, B. T., Voulgaris G., Thieler E. R., 2005. Exploring the persistence of sorted 751

bedforms on the inner-shelf of Wrightsville Beach, North Carolina. Continental 752

Shelf Research, 25, 65-90. 753

Harris, P. T., Heap A. D., Whiteway T., Post A., 2008. Application of biophysical 754

information to support Australia's representative marine protected area program. 755

Ocean & Coastal Management, 51, 701-711. 756

Hernández-Molina, F. J., Fernandez-Salas L. M., Lobo F., Somoza L., Diaz-del-Rio V., 757

Dias J. M. A., 2000. The infralittoral prograding wedge: a new large-scale 758

progradational sedimentary body in shallow marine environments. Geo-Marine 759

Letters, 20, 109-117. 760

Hernández-Molina, F. J., Llave E., Ercilla G., Maestro A., Medialdea T., Ferrin A., 761

Somoza L., Gràcia E., Masson D. G., García M., Vizcaino A., León R., 2008. 762

Recent sedimentary processes in the Prestige site area (Galicia Bank, NW Iberian 763

Margin) evidenced by high-resolution marine geophysical methods. Marine 764

Geology, 249, 21-45. 765

Hovland, M., 2003. Geomorphological, geophysical, and geochemical evidence of fluid 766

flow through the seabed. Geofluids IV Meeting. Journal of Geochemical 767

Exploration., pp. 287-291. 768

Hughes Clarke, J. E., Mayer L. A., Wells D. E., 1996. Shallow-water imaging 769

multibeam sonars: A new tool for investigating seafloor processes in the coastal 770

zone and on the continental shelf. Marine Geophysical Researches, 18, 607-629. 771

Iberinsa, 1990. Estudio geofísico marino entre la frontera Francesa y Ondárroa. 772

Realizado para el Ministerio de Obras Públicas y Urbanismo (in Spanish). 773

Iberinsa, 1994. Estudio geofísico de la costa de Bizkaia. Realizado para el Ministerio de 774

Obras Públicas, Transporte y Medio Ambiente. Dirección General de Costas (in 775

Spanish). 776

IGME, 2005. Instituto Geológico y Minero de España. Área de Cartografía. Mapa 777

Geomorfológico de España y del margen continental. 1:1.000.000. 84-7840-591-7 778

(in Spanish). 779

Irish, J. L., Lillycrop W. J., 1999. Scanning laser mapping of the coastal zone: The 780

SHOALS system. ISPRS Journal of Photogrammetry and Remote Sensing, 54, 123-781

129. 782

Jouanneau, J.-M., Weber O., Champilou N., Cirac P., Muxika I., Borja Á., Pascual A., 783

Rodríguez-Lázaro J., Donard O., 2008. Recent sedimentary study of the shelf of the 784

Basque country. Journal of Marine Systems, 72, 397-406. 785

31

Klingebiel, A., Gayet J., 1995. Fluvio-lagoonal sedimentary sequences in Leyre delta 786

and Arcachon bay, and Holocene sea level variations, along the Aquitaine coast 787

(France). Quaternary International, 29, 111-117. 788

Kostylev, V. E., Todd B. J., Fader G. B. J., Courtney R. C., Cameron G. D. M., Pickrill 789

R. A., 2001. Benthic habitat mapping on the Scotian Shelf based on multibeam 790

bathymetry, surficial geology and sea floor photographs. Marine Ecology Progress 791

Series, 219, 121-137. 792

Kostylev, V. E., Courtney R. C., Robert G., Todd B. J., 2003. Stock evaluation of giant 793

scallop (Placopecten magellanicus) using high-resolution acoustics for seabed 794

mapping. Fisheries Research, 60, 479-492. 795

Lastras, G., Arzola R. G., Masson D. G., Wynn R. B., Huvenne V. A. I., Hühnerbach 796

V., Canals M., 2009. Geomorphology and sedimentary features in the Central 797

Portuguese submarine canyons, Western Iberian margin. Geomorphology, 103, 310-798

329. 799

Liquete, C., Canals M., Lastras G., Amblas D., Urgeles R., De Mol B., De Batist M., 800

Hughes-Clarke J. E., 2007. Long-term development and current status of the 801

Barcelona continental shelf: A source-to-sink approach. Continental Shelf Research, 802

27, 1779-1800. 803

Liria, P., Garel E., Uriarte A., 2009. The effects of dredging operations on the 804

hydrodynamics of an ebb tidal delta: Oka Estuary, northern Spain. Continental Shelf 805

Research, 29, 1983-1994. 806

Llave, E., García M., Pérez C., Sayago M., Farrán M., Ercilla G., Somoza L., León R., 807

Maestro A., Medialdea T., Hernández-Molina F. J., Álvarez R., Durán R., Mohamed 808

K., 2008. Morphological feature analyses of the Prestige half-graben on the SW 809

Galicia Bank. Marine Geology, 249, 7-20. 810

Lo Iacono, C., Guillén J., 2008. Environmental conditions for gravelly and pebbly 811

dunes and sorted bedforms on a moderate-energy inner shelf (Marettimo Island, 812

Italy, western Mediterranean). Continental Shelf Research, 28, 245-256. 813

Lobo, F. J., Fernandez-Salas L. M., Moreno I., Sanz J. L., Maldonado A., 2006. The 814

sea-floor morphology of a Mediterranean shelf fed by small rivers, northern Alboran 815

Sea margin. Continental Shelf Research, 26, 2607-2628. 816

Lucieer, V., Pederson H., 2008. Linking morphometric characterisation of rocky reef 817

with fine scale lobster movement. ISPRS Journal of Photogrammetry and Remote 818

Sensing. Theme Issue: Remote Sensing of the Coastal Ecosystems, 63, 496-509. 819

Marsh, I., Brown C., 2009. Neural network classification of multibeam backscatter and 820

bathymetry data from Stanton Bank (Area IV). Applied Acoustics. The Application 821

of Underwater Acoustics for Seabed Habitat Mapping, 70, 1269-1276. 822

Mary, G., 1983. Evolución del margen costero de la Cordillera Cantábrica en Asturias 823

desde el Mioceno. Trabajos de Geología, 13, 3-35 (in Spanish). 824

Medialdea, T., Somoza L., León R.,. Farrán M, Ercilla G., Maestro A., Casas D., Llave 825

E., Hernández-Molina F. J., Fernández-Puga M. C., Alonso B., 2008. Multibeam 826

backscatter as a tool for sea-floor characterization and identification of oil spills in 827

the Galicia Bank. Marine Geology., 249, 93-107. 828

32

Muñoz, A., Ballesteros M., Montoya I., Rivera J., Acosta J., Uchupi E., 2008. Alborán 829

Basin, southern Spain--Part I: Geomorphology. Marine and Petroleum Geology, 25, 830

59-73. 831

Murray, A. B., Thieler E. R., 2004. A new hypothesis and exploratory model for the 832

formation of large-scale inner-shelf sediment sorting and "rippled scour 833

depressions". Continental Shelf Research, 24, 295-315. 834

Orpin, A. R., Kostylev V. E., 2006. Towards a statistically valid method of textural sea 835

floor characterization of benthic habitats. Marine Geology, 225, 209-222. 836

Pascual, A., Cearreta A., Rodríguez-Lázaro J., Uriarte A., 2004. Geology and 837

Palaeoceanography. Elsevier Oceanography Series. Oceanography and Marine 838

Environment of the Basque Country. Á. Borja and M. Collins (Eds.). Elsevier, pp. 839

53-73. 840

Pickrill, R. A., Todd B. J., 2003. The multiple roles of acoustic mapping in integrated 841

ocean management, Canadian Atlantic continental margin. Ocean & Coastal 842

Management, 46, 601-614. 843

Pittman, S. J., Christensen J. D., Caldow C., Menza C., Monaco M. E., 2007. Predictive 844

mapping of fish species richness across shallow-water seascapes in the Caribbean. 845

Ecological Modelling, 204, 9-21. 846

Portero, G., Salazar A., Pascual M. H., Ortega I., Olivé A., 1991. Puntos de interés 847

geológico de Gipuzkoa. Diputación Foral de Gipuzkoa, San Sebastián, 167 pp. 848

REDMAR, 2005. Resumen de parámetros relacionados con el nivel del mar y la marea 849

que afectan a las condiciones de diseño y explotación portuaria. Puertos del Estado. 850

http://www.puertos.es. 19 pp. (in Spanish). 851

RESON, 2002. SeaBat 8125 Operator´s manual. Version 3.01, pp. 134. 852

RESON, 2006. SeaBat 7125 Operator´s manual. Version 3.0, pp. 89. 853

Rey, J. J., Sanz J. L., 1982. Estudio geológico submarino del litoral cantábrico con 854

sónar de barrido lateral (desde San Vicente de la Barquera a Punta San Emeterio). 855

Boletín del Instituto Español de Oceanografía, VII (I), 88-96 (in Spanish). 856

Rodríguez, J. G., Uriarte A., 2009. Laser Diffraction and Dry-Sieving Grain Size 857

Analyses Undertaken on Fine- and Medium-Grained Sandy Marine Sediments: A 858

Note. Journal of Coastal Research, 25, 257–264. 859

Ryan, D. A., Brooke B. P., Collins L. B., Kendrick G. A., Baxter K. J., Bickers A. N., 860

Siwabessy P. J. W., Pattiaratchi C. B., 2007. The influence of geomorphology and 861

sedimentary processes on shallow-water benthic habitat distribution: Esperance Bay, 862

Western Australia. Estuarine, Coastal and Shelf Science, 72, 379-386. 863

Sagarminaga, Y., Galparsoro I., Borja Á., Beltrán B., Rivas R., 2007. ItsasGIS, the SDI 864

in AZTI-Tecnalia: Evolution, Achievements and New Challenges. CoastGis´07. 865

COASTGIS07, Santander (Spain), pp. 85-91. 866

Stockmann, K., Riethmüller R., Heineke M., Gayer G., 2009. On the morphological 867

long-term development of dumped material in a low-energetic environment close to 868

the German Baltic coast. Journal of Marine Systems. Dynamics of Natural and 869

Anthropogenic Sedimentation, 75, 409-420. 870

33

Thieler, E. R., Brill A. L., Cleary W. J., Hobbs C. H., Gammisch R. A., 1995. Geology 871

of the Wrightsville Beach, North Carolina shoreface: Implications for the concept of 872

shoreface profile of equilibrium. Marine Geology, 126, 271-287. 873

Thrush, S., Dayton P., Cattaneo-Vietti R., Chiantore M., Cummings V., Andrew N., 874

Hawes I., Kim S., Kvitek R., Schwarz A. M., 2006. Broad-scale factors influencing 875

the biodiversity of coastal benthic communities of the Ross Sea. Deep Sea Research 876

Part II: Topical Studies in Oceanography. Ecology of the Antarctic Sea Ice Zone, 877

53, 959-971. 878

Uriarte, A., 1998. Sediment Dynamics on the Inner Continental Shelf of the Basque 879

Country (N. Spain). PhD. Thesis. University of Southampton. 302 pp. 880

Uriarte, A., Collins M., Cearreta A., Bald J., Evans G., 2004. Sediment supply, transport 881

and deposition: contemporary and Late Quaternary evolution. Elsevier 882

Oceanography Series. Oceanography and Marine Environment of the Basque 883

Country. Á. Borja and M. Collins (Eds.). Elsevier, pp. 97-131. 884

Valencia, V., Franco J., Borja Á., Fontán A., 2004. Hydrography of the southeastern 885

Bay of Biscay. Oceanography and Marine Environment of the Basque Country. Á. 886

B. a. M. Collins (Eds.). Elsevier, pp. 159-194. 887

Vázquez, J. T., Medialdea T., Ercilla G., Somoza L., Estrada F.,. Fernández Puga M. C, 888

Gallart J., Gràcia E., Maestro A., Sayago M., 2008. Cenozoic deformational 889

structures on the Galicia Bank Region (NW Iberian continental margin). Marine 890

Geology, 249, 128-149. 891

Wilson, M. F. J., O´Connell B., Brown C., Guinan J. C., Grehan A., 2007. Multiscale 892

Terrain Analysis of Multibeam Bathymetry Data for Habitat Mapping on the 893

Continental Slope. Marine Geodesy, 30, 3-35. 894

Zajac, R. N., 2008. Macrobenthic biodiversity and sea floor landscape structure. Journal 895

of Experimental Marine Biology and Ecology. Marine ecology: A tribute to the life 896

and work of John S. Gray, 366, 198-203. 897

898

899

34

Figure captions 900

Figure 1. Study area location, within the Bay of Biscay. Available geological and 901

geomorphological information in the terrestrial area (modified from (EVE, 2003; 902

Pascual et al., 2004)); the black dots represent the positions of the collected grab 903

samples. 904

Figure 2. (a) Bathymetry; (b) bathymetric gradient and (c) seafloor type distribution and 905

geomorphological map. 906

Figure 3. Seafloor signatures for each seafloor type, identified by integrating different 907

remote sensing techniques: (a) sedimentary seafloor with 1 m resolution shaded 908

relief model, in which sorted bedforms could be identified by the depression 909

they produce; (b) acoustic response of that features; (c) 0.2 m resolution shaded 910

relief, where mixed medium and coarse sand with megaripples at 60 m depth are 911

identifiable; (d) backscatter signal of the same area; (e) 0.2 m resolution shaded 912

relief model, with mixed coarse sand and rocky seafloor at 33 m water depth; 913

and (f) backscatter signal of the same area. 914

Figure 4. (a) Very shallow water depth mixed sandy and rocky seafloor, where 1 m 915

resolution shaded relief is overlapping aerial photography (seafloor feature 916

continuity can be identified); (b) flat rocky seafloor at 1 m resolution shaded 917

relief; (c) integrated topographic LiDAR, bathymetric LiDAR and MBES, on a 918

rocky seafloor (left picture: high rugosity seafloor and soft or low rugosity rocky 919

seafloor); (d) cliff erosion rock blocks, over rock substrate; (e) 1 m resolution 920

shaded relief, on sediment disposal area; (f) backscatter mosaic of the same area 921

(dumped material shows higher backscatter signal). 922

Figure 5. (a) 1 m resolution shaded relief, with suction dredging marks, in Bilbao 923

Harbour; (b) backscatter signal of the same area; (c) submarine outfall. 0.25 m 924

resolution shaded relief; some elements of the infrastructure could be identified: 925

(1 to 8) diffusers, (9) submarine outfall, (10) hard substrate covering and 926

protecting the outfall and (11) fine sand; (d) backscatter signal on the same area. 927

Figure 6. (a) water depth frequency histogram for the total digital elevation model; 928

arrows indicate high slope areas, which are representative of the shore borders 929

location. (b) Depth profile location over rocky seafloor. (c) Extracted depth 930

profile, where various shore borders are identifiable at different water depths. 931

Figure 7. Folk diagram, including all the collected grab samples. 932

Figure 8. Seismic profile record, perpendicular to the longitudinal axis of a sorted 933

bedform. 934

Figure 9. Sorted bedforms: (a) shaded relieve, bathymetry and superficial grab sample 935

positions; (b) bathymetric gradient; (c) seafloor aspect; (d) non-calibrated 936

backscatter mosaic. In the lower part of the Fig. (8) grab sample photographs are 937

presented, which correspond to the locations represented in the upper parts of the 938

Figure. 939

Figure 10. Surf zone sandbars and troughs, observed from 2 m horizontal resolution 940

shaded relief, derived from bathymetric LiDAR DEM. 941

35

Figure 11. Shaded relief of integrated terrestrial LiDAR, bathymetric LiDAR and 942

MBES digital elevation models, at 1 m grid resolution. Continuous lines 943

represent paleo-channel incisions, which are aligned with onshore drainages. 944

Dashed lines represent shore borders corresponding to different sea-level stand-945

still. 946

947

Dear Editor, Please, find below our response to the reviewers’ comments. In order to facilitate your editing work, we have included the lines of the manuscript in which changes have been included. We consider that all of the comments improve the text and we have accepted them. Only in the case of Section 5.3, we discuss the comments of Reviewer 2 (see below). Regards. Ms. Ref. No.: GEOMOR-1653 Title: Morphological characteristics of the Basque shelf (Bay of Biscay, northern Spain); and their implications for Integrated Coastal Zone Management Authors: Ibon Galparsoro*, Ángel Borja, Irati Legorburu, Carlos Hernández, Guillem Chust, Pedro Liria and Adolfo Uriarte Reviewer #1: The work would be improved if you make a small effort for a better characterization of waves and tides and revise the quality of the figures for a grayscale reproduction (see comments on the text and figures). Comments and minor changes suggested by Reviewer #1 in the attached pdf file have been undertaken. Major changes: As suggested by this Reviewer, the wave climate text has been extended (see lines 122-139). A wind rose diagram has been included as supplementary information. On the other hand, we do not think that it is necessary to increase the Section on tidal characterisation; as explained in the text, this is not a critical factor affecting processes on the continental shelf seafloor. Finally, two new references have been included in the text in relation to the mean geomorphological and hydrological characteristics of the Basque estuarine water bodies: Valencia et al. (2004) and Borja et al. (2006) (lines 150-152).

Reviewer #2: Figure 1 - Add European continent Done Line 205, item 3.4 the authors must say how they analyzed the sediment samples. And the methods that they used (Folk and Ward? Shepard?...) Done. A new paragraph has been included within the text and a new reference has been included (now in lines 221-225). Line 258 change above per previous section (it is necessary to check in others parts of paper as well) Done (now in line 275)

*Response to Reviewers

Line 484, item 5.3 must be rewrite (must be shortly) or must be deleted from the paper. The authors presented a very good review about the European legislations or directives , but it is not clear how the results of paper could be incorporated in the ICZM. The author must be direct to the point, because it is clear for all researches and different stakeholder that is important to obtain information about the seascape. This item is repetitive with the introduction as well. We disagree with these particular comments, but are in agreement with comments of Reviewers 3 and 1 (see: “These kind of interdisciplinary studies are becoming of interest to the correct management of coastal areas, according with recent European directives. The knowledge of the physical processes, and the bottom characteristics (rocky or sedimentary, sandy or muddy) and features constitutes the basis to understand the functioning of the supported habitats. In my opinion, State of art and Discussion chapters are very good”). In fact, the title of the paper is: “Morphological characteristics of the Basque shelf (Bay of Biscay, northern Spain); and their implications for Integrated Coastal Zone Management”, because importance is attached to the use of this kind of data for integrated management. Presently, very few studies focus upon this topic; there exists increasing need of applying this information to management (see Discussion). We consider that there is not repetition: in the Introduction we describe the present situation on a global scale (as highlighted by the reviewers) but, in the discussion, we focus on a regional scale (Bay of Biscay); this shows how all the information is being put together with the final objective of the ICZM and MSFD implementation. Hence, we consider that Marine Spatial Planning, within this context, is important and requires some extended explanation. Reviewer #3: a) Figures 2a,b,c are not clear, difficult to read the figure legends, (Needs clarity / modification) We think that this is because the Figures that were sent to the Reviewers have lower resolution than the original ones. The automatic quality control required by the manuscript submission was passed. b) Where are the paleaochannels in Fig 2b, Please show. Done. A new map has been edited and the paleo-river channel axis incorporated c) P.7, line 158 what are bad soundings not clear, is it false/pseudo images or simply noise? The term "bad soundings" used in the text corresponds to the depth values provided by the multibeam that are artefacts, produced by different reasons:e.g. noise, fish schools, underwater objects, bubbles, etc. The sentence used in the manuscript: "Bad soundings were filtered and tide correction was applied", has been changed to: "Incorrect depth values were filtered and tidal correction was applied" (now in line 173) d) P.9 line 185, how accurate are these shallow water bathymetric systems. Please provide latest reference. Two sentences have been included for each bathymetric systems: For the multibeam system: "The operational frequency of the system was 400 kHz, producing 256 beams, in a 128º angle swath with a system depth resolution of 6 mm." (now in lines 169-171)

For the bathymetric LiDAR, we think that the sentence already written is sufficient: "Vertical accuracy (i.e. RMSE), compared to known points from the existing survey, was of the order of ±0.25 m." (lines 204-206) e) The infra-littoral prograding wedge (p.14 and Fig 8) not clear. You may care to refer Hernandez Molina's (GML, 2000) work on this aspect Within the text, its morphology has been described according to seismic profile records and multibeam bathymetry. We consider that the feature morphology coincides with the IPW described in the cited Hernandez Molina´s paper. The reference has been included as an explanation of such type of morphology, process and location, at other locations on the Spanish continental shelf. (line 423). f) P.16, Line 344, it is "anthropogenic" rather than human induced, use accepted terms Done g) P.18, line 410, Are the sand banks the IPW?, then check e) The IPW is a morphological feature which has been identified in the major sand banks (line 423). i) P.18, line 395, what is meant by rock strata? Is it a sedimentary strata? Original text: "The disposition of the rock strata is an important factor controlling the coastal and shelf configuration". Corrected text: "The disposition of the sedimentary rock strata is an important factor controlling the coastal and shelf configuration". (line 406) j) P.18, line 407, delete "to seawards" and start word with "The continental shelf appears as a sedimentary Neogene and Pleistocene prism, developed by..(Reference....)". Done (line 418)

Figure01 colour for online versionClick here to download high resolution image

Figure01 greyscale for printed versionClick here to download high resolution image

Figure02 colour for printed and online versionsClick here to download high resolution image

Figure03 colour for online versionClick here to download high resolution image

Figure03 greyscale for printed versionClick here to download high resolution image

Figure04 colour for online versionClick here to download high resolution image

Figure04 greyscale for printed versionClick here to download high resolution image

Figure05 colour for online versionClick here to download high resolution image

Figure05 greyscale for printed versionClick here to download high resolution image

Figure06 colour for online versionClick here to download high resolution image

Figure06 greyscale for printed versionClick here to download high resolution image

Figure07 for printed and online versionsClick here to download high resolution image

Figure08 colour for online versionClick here to download high resolution image

Figure08 greyscale for printed versionClick here to download high resolution image

Figure09 colour for printed and online versionsClick here to download high resolution image

Figure10 colour for online versionClick here to download high resolution image

Figure10 greyscale for printed versionClick here to download high resolution image

Figure11 colour for online versionClick here to download high resolution image

Figure11 greyscale for printed versionClick here to download high resolution image

Supplementary material for online Figure01Click here to download Supplementary material for online publication only: SupplMat_01.tif

Supplementary material for online Figure02Click here to download Supplementary material for online publication only: SupplMat_02.tif

Supplementary material for online Figure03Click here to download Supplementary material for online publication only: SupplMat_03.tif

Supplementary material for online Figure04Click here to download Supplementary material for online publication only: SupplMat_04.tif

Supplementary material for online Figure05Click here to download Supplementary material for online publication only: SupplMat_05.tif

Supplementary material for online Figure06Click here to download Supplementary material for online publication only: SupplMat_06.tif

Supplementary material for online Figure07Click here to download Supplementary material for online publication only: SupplMat_07.tif