Newhaven Flood Alleviation Scheme East Sussex &

Oxford Archaeology (OA) was commissioned by JacksonHyder on behalf of the
Environment Agency to undertake an eight trench evaluation and borehole survey at
the site of a proposed Flood Alleviation Scheme in Newhaven, East Sussex (NGR TQ
4470 0110). The work aimed to assess the impacts of the proposed scheme, which
comprised a variety of newly constructed flood embankments or improvements to the
existing defences along the river Ouse. A programme of five trenches and a borehole
survey were undertaken across the main impact areas of the scheme in October 2015.
The work followed on from a desk-based deposit model developed for the site that
identified a sequence of alluvial and organic deposits on the western bank of the river
at depths between 4m and 5m. The upper surface of mid-Holocene peat sequences
have previously produced evidence of prehistoric activity in similar valley sequence,
most notably at Shinewater, in the Willingdon Levels. Thick made-ground deposits were
also identified between 0.30m and 4m close to the historical core that were poorly
defined and required further field investigation.
The trenching identified modern made-ground deposits to an average thickness of
1.8m. Below this, the trenches generally exposed historical levelling deposits derived of
17th-19th century demolition. Chalk or pebble gravel layers were noted in places,
where they were also associated with ground-raising episodes. The estuarine
sequence was not encountered due to the 2m limit on the trench depths. No significant
archaeological features or structures were encountered during these works.
The borehole survey identified a sequence of alternating silts and sandy deposits,
representing estuarine sedimentation below various ground made-up layers. No
evidence of peat deposits or the presence of Head gravels were noted within the
samples.
The only find of note was a residual crested flint blade from the made-ground deposits
within Trench 4. This could date from the upper Palaeolithic to the Neolithic, but more
precise dating is not possible based on a single blade. The presence of Palaeolithic
assemblages have been previously identified from peri-glacial features within the
surface of the Head gravels close to the site.
Based on the results of the field investigations, the proposed scheme impacts are
confined to the modern made-ground deposits, which are considered to have limited
archaeological or palaeoenvironmental potential.
&
Oxford Archaeology was commissioned by Arcadis on behalf of the Environment
Agency, to develop a geoarchaeological deposits model for the Newhaven Flood
Alleviation Scheme, East Sussex. The Scheme is designed to offer improved flood
protection for the town of Newhaven from the River Ouse. The Scheme covers a
total of 0.55km² (55 hectares) which has been sub-divided into five areas - two on
the west bank of the river (Area 3 and 4) and three on the east bank (Areas 1, 2 and
5)
Following the recommendations made in the Cultural Heritage Statement and in
consultation with East Sussex County Council, an updated site deposit model was
developed for the Scheme using data from 40 geotechnical boreholes, a proportion
of which was not available to the original 2015 geoarchaeological study.
The model demonstrates a considerable depth of Late Glacial deposits and
Holocene alluvium (up to 26m in depth) preserved within the Ouse Valley. Deeply
incised valley sequences like the mouth of the Lower Ouse were in-filled with marine
and estuarine sedimentation following the rapid rise in sea-level at the end of the
last glaciation. Pleistocene sandy gravel deposits were identified at the base of the
sequence between 26m to 18m in depth, and were mostly identified on the east
bank, due to the greater depth of sampling within this area.
Basal lower organic and alluvial deposits were recorded overlying the gravels but
their formation and date have yet to be fully established. These deposits were
sealed by sandy gravel deposits representing either beach gravels and/or Head
deposits located between 18m to 4m (-22m to -8m OD) on the eastern bank and 5m
to 3m in depth (0m to +2m OD) on the western bank.
The Holocene sequence were sand dominated estuarine deposits with marine shells
and tidal laminations. This corresponds with an increase in sedimentation across the
South Coast related to marine inundation of the valleys during the mid Holocene.
They vary in thickness from 8m to 20m, accumulating between -22m aOD to +2m
aOD.
On the western banks the estuarine sands are not recorded at similar depths
indicating that the main Ouse channel was originally located on the eastern bank.
During the medieval period the mouth of the Ouse was located further east at
Seaford and the course of the current river is a more recent man-made
development. In contrast the western bank, is dominated by silty clay and organic
alluviums indicating lower-energy deposition away from the main estuarine channel.
A sequence of alluvial and organic deposits were recorded on the western bank.
The upper surface of these mid Holocene peat sequences have previously
produced evidence of prehistoric activity in other valley sequence, most notably at
Shinewater, in the Willingdon Levels and within the Combe Haven, Bexhill. The
absence of significant organic deposits on the east bank may limit the
archaeological and palaeoenvironmental potential in this area.
The accumulation of the upper alluvial deposits of inter-digitating silts and silty clays
mark a major phase of marine incursion and channel migration recorded across the
sequence. Similar incursions by the sea at this time are recorded at a number of
other locations along the coast of England and is often referred to as the ‘Romano-British Transgression’. It is widely believed that large-scale deforestation and
sediment availability may have also played a significant role in the increased
flooding and rising water-levels in many of the valleys during this period. The
weathered upper surface of the alluvium reflects the drying out and the beginning of
reclamation of tidal flats during the early medieval period.
Thick made-ground deposits between 0.30m to 4m were identified overlying the
alluvium sequence, which requires further investigation and characterisation. The
nature of these deposits is poorly defined within the geotechnical logs and could
contain archaeological horizons and deposits. The west bank and area around the
historical core will in particular need further investigation to establish the
archaeological potential in these areas.
The results of the deposit model have demonstrated significant potential for
palaeolithic and early prehistoric remains to be impacted within Scheme Areas 3
and 4. The thickness and poorly defined nature of the made-ground deposits close
to the historical core also has the potential to contain historical archaeological
remains.
The preliminary deposit model was based on paper records only and would benefit
from further development based on biostratigraphic assessment and dating of
organic deposits. The confusion over the basal sequence of organic alluvium
underlying sandy gravel in particular can only be resolved through further sampling
and a programme of suitable dating techniques.