St Katherine's Chapel

The possible site of St Katherine's Chapel covers an area of 183m2, containing a discrete debris field composed of relatively small masonry rubble blocks (1.91 length:width ratio) that average 1.54m by 0.84m, with a swath bathymetry derived height of 0.3-0.6m (2012 MBES). The vicinity of the target is associated with a single unidentified building on the 1587 Ralph Agas map. It lies north of the centre of the town, 226m NNE of the ruins of St Peter's church. The small area of the debris field, combined with the relatively discrete blocks and debris field we interpret to reflect a smaller chapel site rather than another church. Size analysis of the 10 largest blocks at each site, reveals that this site is composed of smaller blocks, and is statistically different to the other Church sites (t-test, P<0.001). Bacon (1982; 1988) reports finding carved imposts and other worked masonry from a site that fits the location of this structure. The recovered materials strongly support an ecclesiastical origin, though none of the DIDSON or multibeam data can confirm this. At present therefore this structure remains unidentified, though it was clearly present as a building in 1587. It's vicinity to St Johns raise the possibility of it being St Katherine's Chapel. It is reported to have been lost around the same time as St Johns Church (c.1550+, Gardener 1754), but coastal retreat analysis puts it as later (c. 1650). Further investigation of the site is required in order to confirm its origin and to identify the status of the building.

3D visualisation of the possible St Katherine's Chapel site based on 2012 R2Sonic Multibeam survey. The high resolution MBES picks up the rough surface of the rubble masonry and the scour pits around the blocks

Top left - 2012 Multibeam at 5cm resolution. Top Right 2012 Sidescan Sonar at 2cm resolution. Bottom left shows the Bathymetric change at the site between 2008-2012. St Katherine's Chapel site has been subject to net removal of fine sediments since 2008, and the formation of scour pits around the larger blocks.

DIDSON-DH images of the possible St Katherine's Chapel site. (L) is a high resolution image of a large masonry block and smaller blocks surrounding it. Note the rough surface of the larger blocks created by stones set in mortar, and marine sponges covering the surface. (C) ripples in fine sediments covering seabed with scour how around masonry blocks. (R) Lower resolution scan of the site showing similar view to 2012 Multibeam.

A DIDSON-DH mosaic of the SE quarter of the site. Red outlines of blocks are digitized from the 2012 Multibeam.
DIDSON data provides much more information than Sidescan and Multibeam alone, and represents a valuable tool for site survey and identification in zero - low visibility conditions.