Full-coverage seafloor mapping in the German Exclusive Economic Zone: interim results on coverage and geodata

Offshore activities and marine environment protection promote the substantial need of habitat maps that sufficiently characterize and represent the abiotic and biotic conditions on the sea floor. Therefore, detailed information of seabed sediment types is essential for a wide range of applications. According to the implementation of EU directives, high-resolution sediment data are a prerequisite for the identification, monitoring and protection of marine benthic biotopes in European marine waters. Midyear 2012, the Federal Maritime and Hydrographic Agency (BSH) of Germany has started a sediment mapping program in cooperation with the Federal Agency for Nature Conservation (BfN) based on side-scan sonar and ground truthing using grab sampler and underwater video. To establish a standardized mapping procedure, BSH and its R&D partners AWI, CAU, IOW and SaM have developed a technical guideline on the requirements for the collection, processing and interpretation of side-scan sonar backscatter data. For the latter, standardized strategies were defined for the classification and discrimination of different seafloor sediment types in order to minimize the subjectivity of expert interpretation. Different levels of classification have been introduced for the sediment types, primarily based on the FOLK scheme. In addition, sand is classified according to the national classification scheme (Figge classification) to meet the requirements for biotope modelling on the sandy shelf of the German North Sea sector. Datasets of sediment distribution include additional information about the genesis of sediment types as well as the type of transition between them. Data collection and processing could be finalized for large areas, older data has been processed and the interpretation of backscatter mosaics according to the guideline is ongoing steadily. Here, the actual status of these works is shown and latest difficulties are discussed.