2023:001 - Woodbrook, Bray, North Beach, Dublin

The proposed coastal erosion protection works will involve building an armour stone revetment to stabilise the cliffs. The engineered slope will extend to the toe of the cliff. At the toe of the cliff, it was necessary to excavate a 300m linear trench within the storm beach as part of these retaining works. The trench extended some 19m eastwards of the cliff.

The linear outer toe trench within the storm beach that required excavation was archaeologically monitored. The trench measured 7m wide x 300m long x 1.5m deep.  Monitoring was carried out between 4^th November 2021 and 26^th January 2022. Monitoring was to the surface level of the prehistoric forest floor. The extent of the submerged forest within this trench was identified.

All archaeological monitoring was done working to the contractor’s schedule and programme. It was only possible to work within 4-hour windows due to the rising tides flooding the site and restricting machine access. The low tides also had to correspond with daylight hours restricting the days available to work.

A second inner toe trench located 6m to the west was subsequently required due to engineering requirements, this was also archaeologically monitored. This area monitored measured 80m x 11m approximately. The forest floor was also identified in this trench and its extent was recorded.

Following specialist advice a detailed archaeological survey was carried out of five cuttings within the submerged forest.

Archaeological monitoring and excavations along a stretch of cliff shoreline immediately north of Bray Harbour revealed stratified deposits of sand, silt and peaty deposits associated with an ancient, submerged forest floor level. At least two levels of forest floor were identified separated by a deep deposit of grey silt (silt deposits =F12 & F33).

The lower or Level 1 forest floor deposits were located at depths of between 0.6m to c.2 below present ground/beach level. Radiocarbon dating of a sample associated with this level (F34 -sample # 17) returned a date of 6610+33 BP (5619-5481 cal BC) placing the Level 1 forest floor at over 6500 years old and within the late Mesolithic (Level 1 forest floor deposits cuttings 1-3 = F14, F18 & F34).

The upper forest floor, Level 2, consisted of a thin peat deposit located at depths of between 0.6m and 0.9m below present ground/beach level.  Radiocarbon dating of a sample associated with level 2 (F25 -sample # 12) returned a date of 5523+33 BP (4446-4331 cal BC) placing the latter forest floor level at over 5500 years old within the late Mesolithic. Thus 1000 years separate both levels of the ancient, submerged forest (Note: BP = before present which is the year 1950).

The deposits, from level 1 and 2, were also sampled for environmental analysis and accessed for insect, plant and wood remains. Overall, the samples indicate an environment of mixed oak pine woodland with standing and flowing water of which there is no modern analogy in Britain or Ireland. Dr Stephen Davis (University College Dublin) has also concluded that the assemblage is of national importance.

The remains of the ancient, submerged forest level were first identified towards the end of the 19th century.  In 1999-2001 a survey of the beach area at the site was carried out by Dr Jason Bolton (Conservation of Architectural and Archaeological Heritage). Bolton identified the remains of up to thirty-five trees partially visible within the foreshore sand deposits. Three samples taken from the tree remains identified all as Scots pine while radiocarbon dating put the forest at over six thousand years old.

In 2020, an archaeological survey of beach foreshore was carried out by ACAS (Aisling Collins Archaeological Services). The remains of at least fifteen trees of the ancient forest were identified. They were often partially covered beneath the beach deposits with only their upper parts protruding. All upstanding features within the study area were recorded in the ‘Archaeological survey for Woodbrook coastal erosion protection works’ report. High tides and storm conditions tend to move the beach deposits around which can reveal more timbers and cover up others – so it’s a constantly changing landscape.

ACAS 45 Richmond Park, Monkstown