The Superficial Deposit Thickness Model (SDTM) is a package of datasets which demonstrate the regional variation in superficial deposits thickness across Great Britain. These deposits are unconsolidated sediments which lie on top of bedrock and may include river channel and floodplain deposits, beach sands, talus gravels and glacial drift and large areas of peat. Superficial deposits are of importance for geologists, civil engineers, hydrogeologists and environmental scientists as they are often unconsolidated and, together with other processes, form pathways for groundwater to travel along. Their thickness over much of the country relates to the glacial history of the UK over the Quaternary period. SDTM datasets combine borehole data records and mapped superficial and artificial geology (at 1: 50 000 scale). SDTM comprises four raster layers; • the Terrain Adjusted Model (TAM) • the Observation Driven Model (ODM) • the Rockhead Elevation Model (RHEM) • the Data Distance (DataDist) uncertainty layer These component layers provide the user with 50m x 50m cell size rasterised surfaces of potential superficial sediment thickness distribution across Great Britain as well as information on the distribution of the input data sources. The intended scale of use of this dataset is 1:100,000 with a vertical modelled precision of +/-5m elevation. The dataset is intended for use at national, regional and local scales but not site scales where specific ground investigation works should be undertaken to determine superficial thickness and / or rockhead elevation. An accompanying User Guide (OR25087) can be downloaded from the product webpage https://www.bgs.ac.uk/datasets/superficial-deposit-thickness-model/
