From Alan James – 2 July 2020
Thanks David, that’s a very nice sketch-map isn’t it? Pretty surely based on observation from a vessel sailing up through the Bay, not getting a clear view of the east side of St Mary’s Isle.
What you say about the relative sea-level is pretty consistent with Peter Friend’s account in his Collins New Naturalist ‘Scotland’ 2012, 59 – 62 and 87 – 91. As his figs. 43 and 56 show, in the past 3500 yrs or so, there’s been a fairly steady drop of at least 0.5mm p/a, which over the centuries would have made enough difference for spring tides to encroach on, and storm surges to flood, over several locations that are now dry land. As well the slow retreat of the sea, the formation of dunes and shingle bars whould have modified the geography – that may apply to the St Mary’s Isle isthmus, maybe even to the lowest part of St Cuthbert St. And I’m sure Senwick was, when the Scandinavians named it, at the head of a sandy creek, sand vík, a good half-mile inland from the present head of Brighouse Bay. It would also explain the location of the Roman fortlets on the Fleet and the Bladnoch, at crossing-points above where the tide normally reached 2000 years ago.
All the best