A DESCRIPTION OF NET SEDIMENT TRANSPORT FOR CARMARTHEN BAY, WALES

On behalf of the National Assembly for Wales, a Sediment Trend Analysis (STA^®) was performed on about 1500 sediment samples collected from Carmarthen Bay, Wales. The latter is a large embayment on the north coast of the Bristol Channel, which is exposed to both Atlantic seas and a macro tidal environment. STA, a technique to determine net sediment transport pathways and the dynamic behaviour of the bottom sediments, was applied as part of a program to assess the resources and constraints to mining of sands and gravels. The results of the STA suggested that the sediments in Carmarthen Bay are divided into a number of parting and meeting zones. To a great extent the bay is self-contained with no major exchange paths apparent with the Bristol Channel or Celtic Sea. It was concluded that the bay contains a fairly constant volume of sediment, which is periodically reworked and recycled by extreme events. Based on the analysis, and a variety of other studies the National Assembly for Wales instigated Policy 3 stating that the NAW “will not look favourably on dredging for marine aggregates due to the significance of constraints identified”.