Was the Wansdyke a Canal?

 

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https://explore.osmaps.com/route/30489348/wansdyke?lat=51.39462&lon=-1.89988&zoom=12.2788&style=Leisure&type=2d

Short answer: No.

Long answer: Still no, Robert John Langdon and the "Prehistoric Britain" community (including their Facebook posts and self-published works), posits that this massive dyke was not a fortification but a prehistoric canal or water-filled ditch, dating back to around 5500 BCE or earlier. Drawing on hydrological modelling, LiDAR scans, and claims of minimal silting, proponents argue it served as a navigable waterway linking river systems like the Thames and Bristol Channel during a wetter post-Ice Age era.

This article examines the specific section of East Wansdyke between Shepherd's Shore and West Woods—approximately 16.5 kilometres of undulating ridgeway terrain—and evaluates the canal theory's feasibility. By extracting and analysing elevation data from topographic sources, including Ordnance Survey maps and hiking routes, we reveal why this interpretation is not merely improbable but, to put it bluntly, batshit crazy: a pseudoscientific flight of fancy that ignores physics, geology, and established evidence.

Mapping the Terrain: Elevations Along the Shepherd's Shore to West Woods Section

East Wansdyke's segment from Shepherd's Shore (near the A361 crossing, grid reference SU047661, coordinates 51.394°N, 1.933°W) to West Woods (approximate central coordinates 51.396°N, 1.777°W) traverses the northern edge of the Marlborough Downs, a chalk ridge characterised by dramatic contours and dry valleys. This 10–12 kilometre stretch (extended to 16.56 kilometres in some hiking paths that follow the dyke's remnants) is far from level, featuring bold curves, irregular ascents, and descents that hug the landscape rather than cutting through it like a purposeful canal might.

Based on topographic data from Ordnance Survey maps, LiDAR imagery, and walking routes such as the Wansdyke Path and Mid Wilts Way, the elevations vary significantly:

• Shepherd's Shore (start point): Approximately 175–200 metres above ordnance datum (AOD), starting at around 181 metres in detailed route profiles. This marks the western entry onto the downs, at the foot of rising ground.
• Ascent to Tan Hill: The dyke climbs steadily and sinuously to Tan Hill (grid reference SU085679), peaking at 294 metres AOD—one of Wiltshire's highest points. This involves a net rise of about 110–120 metres over several kilometres, with multiple undulations.
• Milk Hill area: Continuing eastward, the path reaches the plateau near Milk Hill at 295 metres AOD (the county's summit). Here, the terrain plateaus briefly but includes sharp drops into dry valleys before re-ascending.
• Descent toward West Woods (end point): The elevation gradually falls to 160–200 metres AOD, averaging 197 metres with lows around 163–172 metres in the forested eastern sections. The final drop is notable, navigating steeper slopes and crossing farm tracks.

Overall, the profile resembles a rollercoaster: a total ascent of 352 metres (with equivalent descent, yielding a net drop of just 9 metres across the full 16.56-kilometre route). It ascends and descends at least five to six times, crossing dry valleys and high ridges with slopes of 2–5% in places. The minimum elevation dips to about 172 metres at the eastern end, while the maximum touches 295 metres at Milk Hill. These figures, confirmed via OS Maps and hiking apps, underscore the hilly, ridge-hugging nature of the earthwork—ideal for visibility and defence, disastrous for water retention.

The Canal Theory: Intriguing Yet Fundamentally Flawed

Proponents of the prehistoric canal hypothesis cite several features to support their claim. They highlight the dyke's V-shaped ditch (up to 2.5 metres deep with a 4-metre-high southern bank), flat-bottomed sections (allegedly one-third the width for water flow), minimal silting (e.g., 0.9 metres in central areas, interpreted as evidence of long-term water presence), and even fill distribution. The underlying clay-with-flints subsoil is likened to dew ponds for natural water retention, with springs, groundwater, and palaeochannels supposedly feeding the system. Hydrological modelling "dates" it to 5800–5100 BCE by extrapolating declining post-glacial water tables, arguing higher groundwater once allowed permanent flooding without locks. In this view, Wansdyke facilitated Mesolithic trade or transport, its bends adjusting for elevation and rivers occasionally flowing within it (e.g., at Sandy Lane).

Yet, this theory crumbles under scrutiny. The topography alone renders it impossible as a functional water-filled ditch. With 100–130 metres of net elevation change and 352 metres of cumulative ascent over the section, water would not remain static or navigable—it would drain eastward rapidly, seeping into the permeable chalk or evaporating on exposed ridges. Maintaining depth would require segmented ponds, weirs, or locks every few hundred metres, feats of engineering absent from Mesolithic toolkits and unsupported by excavations. People in that era built basic wooden trackways over wetlands, not ridge-top aqueducts spanning counties.

Geologically, the ridge location offers poor catchment; dry valleys and chalk downs ensure rapid drainage, even in wetter Holocene periods. Groundwater levels varied locally, not via a uniform decline curve applicable county-wide, and modern boreholes show tables metres below the ditch bottom. Temporary flooding might occur in heavy rain via springs, but sustained boating? Utterly unfeasible.

Archaeologically, the evidence points squarely to a defensive or territorial role. Excavations at sites like Shepherd's Shore, Brown's Barn, and others yield Roman and post-Roman artefacts—pottery, coins, revetments—with no Mesolithic traces. Dating aligns with the 5th–6th centuries CE, possibly a sub-Roman British barrier against West Saxon incursions (ditch facing north, towards the Thames Valley threat). The name "Woden's Dyke" evokes Anglo-Saxon paganism, not Neolithic hydrology. Gaps in the earthwork (e.g., a 10-kilometre central void) and its alignment with Roman roads further undermine any continuous waterway function.

Why It's Batshit Crazy: Pseudoscience Masquerading as Innovation

To be rude about it—as the theory deserves—this interpretation is batshit crazy, a concoction of cherry-picked data and wishful thinking promoted through self-published books, YouTube videos, and echo-chamber Facebook groups. It reinterprets every feature as "hydraulic" (bends for water levels! Low silting for boats! Flat bottoms for flow!) while ignoring gravity, established digs, and physics. The OS Map profile, with its multiple ups and downs between 600 and 900 feet (183–274 metres), accidentally exposes the absurdity in the theorists' own materials—they acknowledge the elevations but pretend prehistoric ingenuity overcame them without evidence.

This isn't intriguing alternative archaeology; it's physically illiterate pseudoscience, akin to claiming Stonehenge was an alien landing pad or the Earth is flat. It falls apart when confronted with real data: no locks, no consistent water source, no prehistoric parallels. Wansdyke's design—high, visible, north-facing—screams boundary marker, not transport artery.

In conclusion, while the canal theory adds a dash of romantic speculation to Wansdyke's story, it serves best as a cautionary tale against ignoring evidence in favour of vibes. For hikers tracing this scenic path today, the real wonder lies in its enduring earthworks, a testament to ancient territorial ambitions rather than impossible aquatic engineering.