Beneficial use of dredged sediment
Deben Estuary (Suffolk)
The Loders Cut Island project involved using dredge arisings to restore a small marsh area. Sediment from Woodbridge quayside was excavated using a clam-shell bucket dredge and placed on a local area of marsh by the reverse process. A 65ft barge (carrying 70 tonnes or 50m3 each) was used with an aft-mounted excavator. This was suitable for use in the constrained and busy upper estuary. The unloading was done on the top of the high tide with the barge being floated in and out over separate high water periods. In total 1,400m3 silt were placed over two campaigns (in 2015 and 2017). The recharge site was located alongside a small navigation channel that had been historically created (i.e. 'cut') by hand excavation in this part of the upper Deben estuary. The deposits raised a 1,369m2 area of marsh by around a 1m which became a small 'island' at certain high tides. This island was quickly used by roosting birds and the deposits were relatively rapidly colonised by pioneer marsh plants. The first campaign (in 2015) involved the transportation of 16 barge loads of dredge sediment from Ferry Quay at Woodbridge. A visit in 2016 (a year after this first campaign) indicated that the placed material had remained stable and in situ. The upper margins of this deposited strip had a thick cover of Salicornia spp. as well as occasional Sea Aster (6-7 plants) and one Spartina plant. There were also signs of invertebrate burrows and bird feeding on the un-vegetated lower margins on the channel/cut side. During a re-visit in 2019 it was clear that the vegetation cover had increased.