Deep Wreck Site WA1001

Introduction

Side Scan of WreckSide Scan of WreckWreck WA1001 was described by the UKHO as being a small wreck, intact and possibly wooden, at a charted depth of 56m with the surrounding seafloor at only 57m – 58m deep shoaling to 50m to the northwest of the wreck.
 
The wreck was located during this survey using the sidescan sonar and found to be within 10m of its recorded position.
 

Detailed Results

Sidescan Sonar and Magnetometer Data

Side Scan of Whole SiteSide Scan of Whole SiteThe sidescan sonar data consisted of two prospection lines and nine survey lines each approximately 600m long, orientated E-W with a 75m range setting and covering an area approximately 600m x 330m.
 
A further three lines orientated N-S were surveyed over the wreck itself. Forty-eight anomalies were identified.

 

 

Archaeological PotentialNumber within Study Area
High1
Medium6
Low8
Very Low0
Archaeological Potential Rating of geophysical anomalies within the WA1001 Study Area
 
After the sidescan sonar survey, magnetometer survey lines were acquired with nine survey lines orientated N-S and six survey lines orientated E-W. Two magnetic anomalies were identified.
 
The 48 sidescan sonar and two magnetic anomalies were then viewed in the GIS and grouped into 15 sites. Each was given a level of Archaeological Potential:
 
The largest piece of wreckage in this area (WA6100) measured approximately 25m x 10m. It is characterised by an area of reflectors which are brighter than the surrounding seafloor, with evidence of possible structure.
 
Magnetometer ResultsMagnetometer ResultsThis shows that the material is reflecting less energy than the surrounding sediment. These results are typical of saturated wood lying on sand or gravel. This supports the UKHO record that the wreck is wooden and it is independently confirmed by an associated magnetic anomaly of only 4.82nT.
 
From 25m to the SW of the wreck site to 50m to the NE there were four sites of medium archaeological potential (WA6101, WA6102, WA6113 and WA6114) which were all likely to be debris associated from the wreck. The largest of the four, WA6102, was not described as debris but as a seafloor disturbance. This may be because it was a large section of partially buried wreck rather than a piece of debris on the surface.
 
Approximately 180m to the north-east of the wreck is another large piece of wreckage (WA6106) classified as being of medium archaeological potential. It measures approximately 6m x 1m and has a magnetic anomaly of 6.47nT.
 
The final site of medium archaeological potential (WA6112) is 125m to the south of the wreck and is a large area of bright reflection which may also have been part of the wreck.
 
We cannot be sure that all six sites of medium archaeological potential and the number of other smaller anomalies scattered over the area all belong to the same wreck.
 
But if they do, it suggests that, contrary to the UKHO record, the wreck is broken up and covers an area of approximately 300m x 200m.
 
Of the 15 sites identified within the WA1001 survey area, only 3 have relief of around 1m high in the sidescan sonar data. The majority of the sites lie flat on the seafloor and may be slowly being covered by seafloor sediments.
 

Multibeam Data

The multibeam data covers an area of approximately 740m x 540m. The depth of the seafloor ranges from 49m to 58m. As with all multibeam systems, the resolution of the data is a function of water depth and the beamwidth of the system. The Reson 8125 used for this project has a beamwidth of 0.5° and therefore the footprint of the beams over this site was approximately 0.7m.
 
Multibeam ResultsMultibeam ResultsThe main wreck site (WA6100) was located within the multibeam data only a few metres from the position determined by the sidescan sonar data. The multibeam data shows that this section is approximately 23m x 7m; slightly smaller than the measurements from the sidescan data.
 
The multibeam data also shows that the wreck is standing 0.6m proud of the seafloor. This was not observed from the sidescan sonar data.
 
Viewing the raw soundings rather than the gridded surface provided no further information about the wreck.
 
The area is covered by sandwaves that are orientated NW-SE. This implies that the main direction of the currents is perpendicular to this. Immediately to the SE of the wreck is a small scour pit approximately 1m deep, which was not detected in the sidescan sonar data.
 
information on the ROV survey of this site.