Morpho-sedimentary and -dynamic characteristics of the Bay of Somme Michel C.a, Le Bot S.a, Druine F.a, Costa S.ac, Levoy F. b, Brunaud C.b and Lafite R.a [email protected] a : Normandie Univ, UNIROUEN, UNICAEN, CNRS, M2C, 76000 Rouen, France b : Normandie Univ, UNICAEN, UNIROUEN, CNRS, M2C, 14000 Caen, France c : Normandie Univ, UNICAEN, CNRS, LETG, 14000 Caen, France 1°0'W 0°0' 1°0'E 2°0'E 1°30'E 1°35'E 1°40'E 1°30'E 1°35'E 1°40'E N N SEDIMENT MAP N DYNAMIC MAP Rue Rue N N Sedimentological Dynamic zonation on the ' ' 6 6 zonation in 2013: 2011-2013 period: 1 Bay of 1 Pointe de Pointe de ° ° 0 Somme 0 St-Quentin S1 Muddy sand and sandy mud, St-Quentin D1 Stability 5 5 poorly sorted, with a strong D2 Eastern English Channel La Maye La Maye Picardy CaCO3 content D2 Strong dynamics due to migration of bedforms S2 Sand, moderately sorted to well sorted, with a low CaCO3 content D3 Strong dynamics due to D1 channel migration S3 Sand and slightly gravelly sand, Le Marais moderately sorted, with a very Le Marais 10 10 low CaCO3 content 10 N N D2 D2 ' ' Dynamic zonation N ' 4 4 CaCO3 content in 2013 (%) 0 1 1 S2 Lowest Astronomical Tide ° ° Bay of ° 0 0 0 Sedimentological zonation 5 5 Seine 5 Lowest Astronomical Tide Altimetric variation on the 10 40 20 30 02/06/2012-01/04/2013 Le Crotoy D2 Le Crotoy Mean grain size in 2013 D2 period (m) S3 (µm) 4.17 1.5 ± Le Hourdel 62 - 100 Le Hourdel English Channel 100 - 150 D3 Normandy 1.0 N N 1 150 - 200 ' ' S 2 2 1 1 200 - 250 ° ° 0.5 0 0 D1 5 5 La Mollière 250 - 300 La Mollière 10 10 300 - 350 0 Brighton N Brighton ' 350 - 400 D1 0 FRANCE ° Cap Hornu Cap Hornu -0.5 9 Atlantic 400 - 450 Cayeux- 4 Cayeux- Ocean 450 - 500 sur-Mer Saint-Valéry- La Somme sur-Mer Saint-Valéry- La Somme -1.0 sur-Somme 500 - 550 sur-Somme 0 50 100 Km 0 100 200 Km 0 1 2 Km 550 - 588 0 1 2 Km -1.5 -5.97 1°30'E 1°35'E 1°40'E 1°30'E 1°35'E 1°40'E MORPHOLOGY MAP INTERPRETATIVE MAP N N Rue N Morpho-sedimentary and Morphological zonation:* ' 6 -dynamic zonation on the 1 Pointe de Rue M1 Salt marshes ° 2011-2013 period with 0 St-Quentin 5 N information on filling stage: ' M2 Tidal channels 6 La Maye 1 Z1 Filled (nd) ° M3 Sedimentary bars 0 4 5 Pointe de Z M4 Hydraulic dunes Z2 Final stage of filling St-Quentin 1 (+0.088 ± 0.17m3/m2) Z 3 Z M5 Beach of high altitude M3 La Maye Z3 Final stage of filling Le Marais 3 2 * zones indicate the dominant morphological features observed Z 2 (+0.164 ± 0.17m /m ) on the 2011-2013 period (in case of change on the 2011-2013 3 2 period, salt marshes, tidal channels, sedimentary bars and then Z 5 Z4 Current filling (+0.065 ± 0.17m /m ) N Z 5 dunes have been favored). ' 4 Z5 Current filling 1 ° (+0.156 to +0.249 0.17m3/m2) M1 Morphological zonation 0 ± 5 5 3 2 M Lowest Astronomical Tide Z6 Current filling (+0.372 ± 0.17m /m ) Crests of intertidal bedforms interpreted Le Crotoy Z7 Current filling (nd) Z 8 from LiDAR data (01/04/2013) : Z 5 Z8 Erosion (-0.508 ± 0.17m3/m2) Le Marais Hydraulic dunes Le Hourdel Filling values according to Michel (2016) Z 7 Incertitude according to the formulae of Sedimentary bars Z 8 Z 6 M4 Brasington et al. (2003) N ' M4 Topography of 01/04/2013 N ' 4 Morpho-sedimentary and 2 1 (m NGF-IGN69) 1 ° -dynamic zonation ° 0 13.3 0 5 Z 1 Lowest Astronomical Tide 5 La Mollière 12.0 Brighton Proportions of sedimentary M4 10.0 Z 1 classes, average mean grain Cap Hornu size and carbonate content in 8.0 Cayeux- 2013 (individual samples in Z1 or mean sur-Mer Le Crotoy 6.0 Saint-Valéry- La Somme values per zone in Z2 to Z8) : M4 sur-Somme 4.0 0 1 2 Km Sedimentary classes proportions* 2.0 Sand Fine sand Mud Le Hourdel References : 0 Brasington, J., Langham, J., Rumsby, B. (2003) Methodological sensitivity of morphometric estimates of coarse fluvial sediment transport. M3 * Gravel is not represented as it represents Geomorphology, 53 (3-4), 299–316. never more than 0.76% -2.0 Michel, C. (2016) Morphodynamique et transferts sédimentaires au sein d’une baie mégatidale en comblement (Baie de Somme, Manche Est). M2 Mean grain size -3.6 Stratégie multi-échelles spatio-temporelles. Thèse de doctorat, Université de Rouen. 325 pp. + annexes 400 µm N ' 240 µm (maximum) 2 1 MAP INFORMATIONS ° Data: 0 0 5 M1 CaCO 3 content Reference system : - Sediment map: superficial sediment sampled in 2013 (Michel, 2016) La Mollière - Morphology and dynamic maps: 6 topographic LiDAR survey between 50% Spheroid: RGF93 2011 and 2013 : 31% (maximum) Brighton Projection: Lambert Conformal Conic (Lambert-93) - 17/02-08/03/2011 (RGE ALTI®, IGN) 0 - 28/09/2011 (CIRCLE, SNO DYNALIT, FR SCALE 3730) M1 Location map : Sediment dynamics Cap Hornu - 02/06/2012 (CIRCLE, Région Picardie, FEDER) (2011-2013) : Base map: BD ALTI® (IGN) Cayeux- - 18/11/2012 (CIRCLE, SNO DYNALIT, FR SCALE 3730) Stable areas Administrative boundaries: GEOFLA® Départements - 01/04/2013 (CIRCLE, Région Picardie, FEDER) sur-Mer Saint-Valéry- - 04/11/2013 (CIRCLE, SNO DYNALIT, FR SCALE 3730) Areas of low dynamics Sediment, morphology, dynamic and synthesis maps : sur-Somme La Somme For morphology and dynamic maps, there is no data recorded in water areas (e.g. Areas of strong dynamics Base map: RGE ALTI® version 2.0 (IGN) covered with sedimentary bars channels or hunting ponds located in salt marshes). Most of these zones appears (red) or hydraulic dunes (blue) Elevation scale (m) 0 1 2 Km in transparency on topography. Areas of strong dynamics -2.8 56 due to channel migration © Journal of Maps, 2017.