Thursday, 29 June 2017
Using earthwork survey to record First World War practice trenches in the Sherbrook Valley - An update from Historic England's archaeological investigation team
Earlier this year project volunteers took a closer look on the ground some of the earthwork features identified in the lidar and other aerial sources.
A number of two-day sessions were run by archaeological investigators from Historic England (specialists in researching and recording remnants of historic landscapes) to train local volunteers in the use of basic archaeological survey techniques so that they can continue to add to the growing body of knowledge about the history of the Chase.
Volunteers learned how to produce detailed measured drawings of the earthworks using traditional survey methods - tapes to create baselines, right angles and off-sets, and simple levelling tools to record profiles - as well as how to create short written descriptions and how to take record photographs.
Volunteers measuring the military practice trenches using tape and off-set techniques © Historic England
The first site that we tackled together is near the southern end of the Sherbrook Valley, and it showed up really well in the lidar data. It comprises an L-shaped arrangement of narrow military practice cut in the classic 'Greek key' pattern (a crenelated outline). Beside the trench there are also lots of circular pits surrounded by doughnut-shaped mounds.
Digital terrain model (DTM) from the lidar, showing the military practice trench (centre) and circular pits. Chase Through Time 2016 lidar. Source Staffordshire CC/Fugro Geospatial BV 2016 © Historic England
First the area surrounding the site was explored to better understand its context. Then using long tapes as baselines we took a series of measurements at right angles from these to record the top and bottom-line of the trenches, pits and any associated mounds of earth. By carefully plotting these measurements onto a drawing board we were able to produce an accurate plan. We used a scale of 1:100 (1cm on paper = 1m on the ground) to draw the site, this allowed us to capture as much subtle detail as possible and also provided a straightforward starting point for learning how to draw to a set scale.
Because this method of survey only collects dimensions in 2D, the volunteers added 3D data by taking a number of spot height readings across the site and to record a profile (measured height/depth model) across one of the best sections of the trench.
Extract from one of the earthwork survey field drawings and an inset showing how measurements were plotted using a set square and metric scale rule © Historic England
The separate pencil field survey sheets were scanned and digitally traced to create a single metrically-accurate drawing. Symbols known as 'hachures' (like tadpoles with triangular heads) are used to show how steep, gentle, prominent or vague the slopes are – the 'heads' are drawn at the top of the slope with the 'tails' running downwards. Our spot height measurements were also incorporated to better explain the depth and shape of the trench.
The completed digital survey drawing © Historic England
This group of features would have been used during the First World War to train young soldiers before they were sent into battle. The width and depth of this practice trench (about 0.9m x 0.6m, ie 3ft-wide and 2ft-deep) suggests that it was a ⅓-scale model. This was quite common - although this is the best example we have found, other instances of the same scale are known elsewhere on the Chase.
Extract from a postcard showing solider posed in a practice trench on Cannock Chase which appears to be of a similar small scale to those we surveyed © Arthur R Lloyd Collection
Spending time recording these features in detail meant that useful observations were made. For example, it is clear that the north-west and north-east sides of the L-shaped trench arrangement represented those facing the enemy; the earth dug out to create the trench was piled up along this forward side to make a protective parapet of sorts, much like that in the image above. The uneven nature of this mounded earth, often in distinct separate heaps, shows where each man created an individual pile of soil while he was shovelling.
Volunteers also noticed that the shape of the trench itself was quite complicated. As well as the classic rectangular wiggles of the 'Greek key' pattern, there are deep rounded niches projecting from some of the corners on the front side, these have been interpreted as imitating forward gun-firing or grenade-throwing positions. Smaller rectangular ramped niches projecting back at various points along the rear side might have indicated where the communication trenches would have joined the front line and could also have proved access down into the practice model.
One of a fascinating set of wartime postcards hand-drawn by Erskine Williams on display digitally at the Museum of Cannock, this one shows how the full sized practice trenches at Brocton Camp were used for grenade-throwing © Daphne Jones, reproduced by kind permission of Daphne Jones
The circular pits appear to simulate shell holes and would have provided obstacles and positions for occupying during simulated manoeuvres. How they were created is trickier to prove. The earth mounded around their tops is too neat and uniform to have been created by explosives dropped from the air; however, could they have been created by controlled explosions or might they have been dug by hand to mimic holes left by shells or grenades?
Working in all weathers - taking spot heights with the dumpy level in falling snow! © Historic England
With their hard work the volunteers have created a valuable new record to feed into the project, helping to better understand the wider patterns of land use in Cannock Chase. This is only a tiny fragment of the extensive First World War training areas found across Cannock Chase. We may return to look at some of the other good examples of practice trenches and other features simulating battlefield scenarios, in future blog posts.
With Alidade and Tape: Graphical and plane table survey of archaeological earthworks | PDF download page: https://historicengland.org.uk/images-books/publications/with-alidade-and-tape/
The Light Fantastic: Using airborne lidar in archaeological survey | PDF download page: https://historicengland.org.uk/images-books/publications/light-fantastic/
Identifying First World War trenches | Home Front Legacy 1914-18, case study webpage: http://www.homefrontlegacy.org.uk/wp/case-studies/identifying-first-world-war-trenches/
Jones, D (1992) Bullets and Bandsmen: The story of a bandsman on the Western Front | the story of Erskine Williams illustrated with his autobiographical sketches, written by his daughter
We want your feedback! If anyone has a particular interest in First World War training landscapes and can help by adding further information, interpretations or examples similar to the site mentioned in this post, please leave a comment below.
Archaeological Investigator, Historic England
Find out more about Historic England's contributions to the wider project here: https://historicengland.org.uk/research/research-results/recent-research-results/west-midlands/cannock-chase/