Developments in Seabed Mapping Jon Evans Jon.evans@noc.soton.ac.uk I’m going to give a brief talk and update about our habitat mapping program and recent progress we have made. Shows some examples of the areas we have mapped and reported on this year Brief overview of how the maps are created and what data is required How the various data types help identify certain habitats and sediment types Future uses Developments in Seabed Mapping

Swath bathymetry data extent Red– bathy data commission by the monitoring program – and meets the IHO order 1a swath bathy Blue– Areas mapped Habitat mapping data extent

Anthropogenic Features Seabed Mapping Bathymetry Backscatter Ground Truthing Seabed Habitats: Basic Anthropogenic Features Substrate Type How they are created. Firstly we need high quality multibeam bathymetry data – IHO order 1a – if the bathy data meets this standard and has 100% coverage we can use this and the backscatter data that is collected simultaneously and combine this with a variety of ground truthing data. Backscatter – secondary, but improving with technology Sediment sampling part of spec and other groundtruthing from divers, IFCAS, wildlige trust etc Using this data a number of features and maps can be created including…. Seabed Habitats: Detailed

Example of bathymetry data

GROUNDTRUTHING Examples of groundtruthing – very important when trying to set boundaries etc

Hillshade – Creates a shaded relief from a raster layer Hillshade – Creates a shaded relief from a raster layer. a hillshade layer was derived which is a form of artificial sun-illumination which helps to enhance depth changes and features in the bathymetry dataset. Slope – Identifies different levels of slope gradient. This layer helps distinguish those areas of the seabed that have a steep gradient or sharp changes in slope, and those areas which are relatively flat. Got some examples of where these types of data are useful to back each other up

Beachy Head, East Sussex Extensive rock platform Also where ground truthing points are useful to help set boundaries Different sediment types can be defined

Seaford, East Sussex Underlying bedrock can be clearly identified using the backscatter layer

Beachy Head, East Sussex Extensive rock platform and rocky ridges Geology continues offshore Steep drop off

Chichester Harbour Entrance Narrow, deep channel cutting though shallow sediment

Anthropogenic features – Shoreham Harbour, West Sussex

EUNIS Level 3 marine habitat classifications Rock Rock and thin Sediment Sediment High energy littoral rock Moderate energy littoral rock Low energy and thin Littoral mud sand mixed sediment coarse infralittoral rock and thin Sediment Sublittoral circalittoral Aim from these data types is to create a habitat map and a substrate map Using these various layer the bathymetry is initially divided into areas of rock, rock and thin sediment and sediment. Once we are confident in these boundaries we use the MLWS to split the littoral and sublittoral areas apart and also create an boundary between circalittoal and infralittoral boundaries. Often far more complex than a singular depth contour, can change spatially and temporally but one has to be chosen. It is chosen based on sechhi disks depths and also video/ photography / diver data if available. The boundary denotes the change from where habitats are dominated by light. European nature information system We also separate areas in high, low, medium energy using wind and tide data. In the classifications, ‘Rock’ collectively refers to bedrock, stable and artificial substrata (concrete, wood, metal). Mobile cobbles and pebbles with gravel and coarse sand are collectively referred to as ‘Coarse Sediment’. ‘Mixed Sediment’ consists of mixtures of gravel, sand and mud which may contain stones and shells.   The littoral zone lies landward of Mean Low Water Springs (MLWS) with the sublittoral zone seaward of MLWS. For areas of ‘Rock” or ‘Rock and thin Sediment’ the sublittoral zone is split into the infralittoral zone and the circalittoral zone based upon site specific biological parameters ‘Rock and thin Sediment’ is applied to areas with some thickness of surficial sediment through which the underlying bedrock geology is discernible in the bathymetry. JNCC/CEFAS modified EUNIS classification added ‘Rock and thin Sediment’ category

Images courtesy of SCOPAC

Physical substrate Rock & hard substrates Sediments Bedrock Boulder Cobble Sediment Coarse Sediments Sand Mud Mixed

Images courtesy of SCOPAC

Substrate map Habitat map Exposure & tidal stream data Bedform orientation Slope & aspect of bedrock Geology Ground-truthing Backscatter Bathymetry

Images courtesy of Sussex IFCA

Images courtesy of Sussex IFCA

Conclusion Swath bathymetry, backscatter and ground-truthing essential. Improved understanding of: nearshore habitats, geology, seafloor topography wave environment sediment dynamics Informs sediment transport, marine conservation and marine planning. Cuckmere Haven, East Sussex