The ½ñÈÕ³Ô¹Ï Superficial Deposit Thickness Model (SDTM) dataset presents the modelled regional variation in thickness of superficial and unconsolidated deposits across Great Britain. These include sediments of fluvial, glacial, marine or anthropogenic origin that were generally formed during the Quaternary (the past 2.6 million years up to today). The thickness of these deposits signifies the depth down to the top of the bedrock, known as geological rockhead.

The distribution of these deposits is not uniform: sometimes they are thin veneers, sometimes they form large, irregular masses, and sometimes they infill entire valleys. The latest SDTM release, the first for over 15 years, includes a raster model of the elevation of rockhead for the first time, providing important data for a variety of different sectors.

The transition between superficial sediments and geological rockhead (and associated bedrock units) is an important zone for geologists, civil engineers, hydrogeologists and environmental scientists because it is where most physical and chemical properties of the deposits significantly change. Properties such as strength, lithology, conductivity, porosity and permeability can be strongly affected by this transition, so an understanding of the depth of the transition zone beneath the ground surface is vital.

The SDTM models have been created using digital mathematical interpolation techniques, combining observations of superficial thickness from borehole logs held in our archives with mapped superficial and artificial geology extents from the 1:50 000-scale digital geological map of Britain.

Version 8 of the SDTM includes the new layer, the rockhead elevation model (RHEM). This is a raster model of the elevation of rockhead relative to Ordnance Datum, the standard vertical reference system used in Great Britain to measure land elevation. This model provides users with an integer value of modelled depth to bedrock in metres and will be of particular use for creating 3D ground models and understanding the geological structure across a site.

The updated SDTM product also contains the observation driven model (ODM), the terrain adjusted model (TAM) and data distance (DataDist).

Observation driven model

The ODM is a raster model of sediment thickness that interpolates thickness values between boreholes within the mapped superficial extents, giving users an integer value of modelled superficial thickness in metres.

Terrain adjusted model

The TAM is a raster model of sediment thickness derived using a method that combines borehole records, the mapped superficial deposit extents and surface elevation data. This differs from the ODM by considering the ground surface elevation, derived from the model, and gives users an integer value of modelled superficial thickness in metres.

Data distance

DataDist is a raster surface defining the distance of any location relative to the nearest source of thickness information; either the location of a borehole or the mapped boundary of a superficial deposit. This is provided as a pseudo-uncertainty surface relative to the ODM, TAM and RHEM components of the SDTM. The further a location is from a source of thickness data, the more uncertain any values provided by ODM, TAM and RHEM models are likely to be.

New naming conventions

SDTM Version 8 has introduced new naming conventions for the ODM and TAM datasets. These name changes better describe the characteristics of the two datasets and removes confusion or implications relating to the terms ‘basic’ and ‘advanced’ that might imply one model is superior. Both model outputs provide valid options and should be considered in tandem rather than in isolation to understand the models’ constraints.

This dataset release marks an important development for the ½ñÈÕ³Ô¹Ï SDTM and is its first update since 2010. Improved borehole selection criteria have been implemented, allowing the models to benefit from the latest interpretations of ½ñÈÕ³Ô¹Ï-held borehole logs as well as identifying and excluding low-confidence, inappropriate and conflicting boreholes that may have been included in previous versions. As such, the borehole selection underpinning SDTM V8 is considered to be more robust, resulting in a higher confidence model.

Rob Shaw, geospatial analyst and SDTM product developer, ½ñÈÕ³Ô¹Ï.

The intended scale of use of this dataset is 1:100 000, with an average vertical accuracy of +/-5 m elevation. The dataset is intended for use at national, regional and city scales, but not site scales where specific ground-investigation works should be undertaken to determine precise superficial thickness and rockhead elevation.

We are continuing our scientific research on to how to improve the prediction of superficial thickness and will build that into any future update of the SDTM.

For more information on the SDTM datasets, including how to access the data, please visit the STDM product webpage, download the or get in touch with ½ñÈÕ³Ô¹Ï Digital Data (digitaldata@bgs.ac.uk).

Artificial ground is found throughout the country in a variety of places, for example:

• railway and road cuttings and embankments
• foundations under buildings
• the waste and voids from surface and underground mining
• roads
• landscaped parks and golf courses

½ñÈÕ³Ô¹Ï has been creating national geological maps for nearly 200 years and often these maps are the only record of ground being altered by humans.

We are in the process of developing new methods for capturing and representing artificial ground information and we want to ensure that this is as useful and beneficial as possible to the stakeholder community.

Why do we want your feedback?

The aim of this survey is to gain an understanding from you, our stakeholders, about the types of data that are used regularly, why you need that data, and what decisions are made using the data. Mapping of artificial ground is not easy and everyone treats these deposits differently. By providing a standardised method of collecting and displaying artificial ground data there is significant potential to improve the communication of these features.

Interested in getting involved?

We have put together a short survey that aims to capture your thoughts and processes when working with artificial ground data. We value your input and would appreciate you completing this short questionnaire, providing as much context as possible.

Survey deadline extended to 28th November 2025.

In July 2022, the ½ñÈÕ³Ô¹Ï Hazard Products team visited Yorkshire to assess some key geological hazards. The trip was an opportunity for the team to gain insight into the natural processes and geological features that underpin many of the digital data products they develop.

The team has a diverse skill set, from expertise in Python coding and GIS analysis to engaging with stakeholders and developing business relationships with partners and clients. This melting pot of skills allowed the team to consider geological hazards and potential solutions from a unique perspective and prompted useful discussions around translating ½ñÈÕ³Ô¹Ï science into user-oriented digital hazard solutions as well as the quality and availability of input data.

The team spent two days in the field studying a range of geological hazards in action and considered the strengths and limitations of existing ½ñÈÕ³Ô¹Ï geohazard data products to determine areas for future development.

Sutton Bank

Sutton Bank is a near-vertical, around 140 m-high cliff in Jurassic strata representing about 60 million years of geological time. During the last ice age, about 20 thousand years ago, a lobe of ice extended southwards in this lowland area between the North York Moors and the Pennines. As the ice flowed along the western edge of the moors, it gouged out the soft underlying rocks of the Lower Jurassic, leaving the escarpment you see today.

The clifftop panorama showcases a complex lowland landscape underlain by a mixture of superficial deposits and bedrock. As the ice melted and retreated, it deposited till and outwash deposits, which shaped the landscape we see from the viewpoint today. For example, Gormire Lake, located just below the escarpment at Sutton Bank, formed as a result of glacial deposits blocking drainage channels and trapping water behind them.

is situated at the top of the escarpment, with parking, visitor centre, toilets and café. A short walk leads to a viewpoint with a panoramic view across the previously glaciated vale.

This location was really useful to visualise the landscape of the area and understand how glacial periods in Earth’s history had imprinted on this landscape. It provided useful context for the field sites to come.

Jenny Richardson.

Relevant data products

• ½ñÈÕ³Ô¹Ï Geology
• GeoSure
• Superficial Deposit Thickness Model
• ½ñÈÕ³Ô¹Ï Civils

Sneck Yate

Continuing northwards along Cleveland Road from the visitors centre we reach Sneck Yate. Parking is located in a small gravel layby from where it is a short walk over the top of the escarpment to view cambering features.

The geology at this location comprises the same Jurassic strata as the previous site and this sequence of the and the overlying the softer has created a geohazard called cambering.

Cambering involves large-scale stretching, tilting or rotation of more competent blocks of rock over less competent strata, in this case the Oxford Clay Formation. This tilting can result in discontinuities known as gulls opening up parallel to the valley axis, which can range in width from millimetres to tens of metres and may be sediment filled or not even propagate to the surface.

Cambering and associated features such as gulls and valley bulging are all responses to stress relief or ‘unloading’, which results from rapid incision or erosion of the landscape in conjunction with gravitational forces. It is often associated with glacial erosion and retreat.

This site helps us to better understand the processes associated with permafrost, Quaternary conditions and rates of landscape evolution. Improved understanding also informs planning for ground engineering projects.

• More detailed explanation of cambering and associated geological features 

The size and scale of these features can impact significantly on engineering projects, for example, evaluation of clay disturbance as a consequence of valley bulging was critical to the construction of the Empingham dam at Rutland Water and the upper dams of the Derwent Valley. Cambering is not explicitly defined in our current data products and visiting this site prompted useful discussions on the feasibility to improve this.

Russell Lawley.

Relevant data products

• ½ñÈÕ³Ô¹Ï Geology

Hawnby

From the top of the escarpment the team dropped down into Hawnby village. En route, we noted the steep slopes and landslide events associated with particular geological horizons. Here, an impermeable clay layer forces groundwater to the surface where it emerges as springs and in several cases has initiated landslides in the overlying superficial deposits.

Hawnby lies in Rye Dale on the northern bank of the River Rye. River erosion, flooding and water availability can all be considered risks here. The bridge at Hawnby forms a narrow pinch-point in the valley and carries key utilities infrastructure over the River Rye. From 19 to 20 June 2005 there was a major storm event and flooding devastated the area. Damage included the complete destruction of the bridge, removing access to the village and further impacting the community through the loss of utilities.

It is particularly important to understand the geological constraints and potential for flood events, especially in changing climate conditions where storms are more likely to become more frequent and more intense. When the bridge was rebuilt, design improvements were made to allow water to flow across the bridge and road in an effort to prevent the constriction of river flow and associated erosion in future flood events.

Understanding the capacity of the floodplain, the erosion potential of the sediments and the additional influences such as extra water input into the system from springs can hugely help catchment planning and effective adaptation.

Henry Holbrook.

Relevant data products

• GeoScour
• GeoSure

Holbeck Hall, Scarborough

South of Scarborough is the site of the former Holbeck Hall Hotel, which was destroyed by a landslide between 3 and 5 June 1993.

The Holbeck Hall site is underlain by till deposits overlying the at the top of the cliff, with the cropping out on the foreshore and creating a wave-cut platform. This rotational landslide involving about one million tonnes of glacial till cut back the 60 m-high cliff and flowed out across the beach to form a semicircular promontory 200 m wide projecting 135 m outward from the foot of the cliff. This was rotational landslide that degraded to a mud or debris flow and covered the rocks of the wave-cut platform.

The first signs of movement on the cliff were seen six weeks before the main failure, when cracks developed in the tarmac surface of footpaths running across the cliffs.

• More details of the Holbeck Hall landslide

The likely cause of the landslide was a combination of:

• intense rainfall in the prior two months
• poor drainage of the slope
• high pore-water pressure in the slope
• susceptible superficial geology

Coastal defences have since been installed to protect the toe of the slope from further erosion and pore waters are monitored regularly.

We have been investigating using remote sensing terrain data to identify historic coastal mass movement deposits and it was helpful to observe the form and terrain characteristics of this large scale landslide. Landslide morphology is especially complex at the coast where wave action is also an issue.

Sophie Taylor.

Relevant data products

• GeoCoast
• GeoSure landslides
• ½ñÈÕ³Ô¹Ï Civils

Danes Dyke, near Flamborough

Danes Dyke lies on the southern coast of the Flamborough Head peninsula. It consists of a deep, wooded valley running north–south towards the coast.

The steep ravine is a palaeo-valley about 150 m wide and filled with a complex succession of periglacial, glacial and aeolian sediments. The chalk is folded and faulted with structures visible in the foreshore at low tide. Periglacial weathering was likely focused here due to the presence of faults and evidence for periglacial fractured chalk and rubbly chalk gravel can be seen in the cliffs at the mouth of the ravine. These gravels are overlain by till deposited by a North Sea lobe of the last British–Irish ice sheet that emanated from the Grampian Highlands of Scotland and flowed southwards over which is now the floor of the North Sea.

It is important to understand the nature of the boundary between the chalk bedrock and overlying superficial deposits as well as the properties of the different lithologies. Fracturing and weathering also cause weaknesses in the rock, making them more susceptible to failure.

The typically uneven boundary between chalk and till, differential rates of weathering, and chalk dissolution can have impacts on building foundation design, underground utilities and infrastructure projects. Where these features occur inland, they’re often unseen, so being able to visualise this boundary and erosion features at the coast is a helpful exercise when considering measures to mitigate against associated issues

Clive Cartwright.

Relevant data products

• Superficial Deposit Thickness Model
• GeoSure soluble rocks
• ½ñÈÕ³Ô¹Ï Geology
• GeoCoast

Beneath the surface of Great Britain are hundreds of ancient buried valleys, which have now been mapped for the first time by the ½ñÈÕ³Ô¹Ï.

The buried valleys occur across Britain, from a 162 m-deep valley in Grangemouth, Scotland, to a 22 km-long valley under Melton Mowbray, Leicestershire and a 50 m-deep valley under Swansea.

The valleys mostly date from the last ice age, which ended around 11 500 years ago, and are ancient drainage networks from rivers and glaciers that over the years have become partly or completely buried by more recent sediments.

Sometimes a part of the valley peeks above the surface, but more often than not they are completely hidden underground, with no way for hydrologists, civil engineers, planners or construction companies to tell what lies beneath.

½ñÈÕ³Ô¹Ï first identified a hidden valley in the 1870s, under the River Mersey and has been collecting data from thousands of boreholes across Britain since then.

The digital age brought a new opportunity: to collect and collate all the buried valley data in one place and make it publicly available online.

Britain’s buried valleys might be underground, but they could and have had a huge impact on what happens above the surface.

We need to know where these buried valleys are for a number of reasons. They could be a target area for shallow geothermal energy, like in Cardiff. They could be unsuitable places for skyscrapers or bridges to be constructed. They cause problems for groundwater supplies, as they already do in South East England.

We combined historical ½ñÈÕ³Ô¹Ï survey activities with over 200,000 borehole records from our national borehole database to identify these previously hidden features across the UK.

The buried valleys are all across Britain. The whole of the Cheshire basin looks flat as a pancake, but it has lots of features underneath it. These probably formed under an ice sheet that covered the area some 23 000 years ago.

The deepest system is in the middle of Scotland, under Grangemouth. It’s over 162 m deep and absolutely full of clay.

Now that we know where they are, the next stage of the work is to find out what’s in all of them, and whether they could be useful for providing geothermal energy or as a groundwater source for the whisky or manufacturing sectors.

Dr Tim Kearsey, ½ñÈÕ³Ô¹Ï Geologist and project lead.

The Buried Valleys dataset is online now.