Trial of new saltmarsh restoration drag box at West Itchenor
This project was undertaken to restore an area of deteriorated saltmarsh in Chichester harbour. It was also carried out to test a new way of beneficially using dredge sediment developed by Land and Water Services Ltd. The new technique involved firstly depositing sediment on the low shore directly from a spilt hopper barge and then immediately starting to move it up to the saltmarsh zone at the top of the shore using a new 'drag box'.
This new ‘saltmarsh restoration drag box’ (SRDB) was designed, built and implemented by Land and Water Services Ltd. This drag box approach introduces a novel and potentially very valuable way of using relatively consolidated dredged sediment for saltmarsh habitat restoration. Its value lies in the fact that it can place dredge sediment directly onto marsh levels and keep it there without the need for introducing retaining fences and without affecting the productivity (turnaround and cost) of the dredging operations.
This project was part of the Solent Seascape Project and was supported and informed by several partners including the Chichester Harbour Conservancy and CHaPRoN (see link below). This work is being pursued through adaptive management to build confidence in the approach. An initial trial was undertaken in February 2023. Monitoring is being undertaken at this site by ABPmer to understand how the area performs physically and ecoligically.
Over the course of first year the findings were very encouraging. The imported sediment was poorly consolidated when it was first moved but it stabilised and compacted quickly. It then remained where it was placed throughout the year. Some Samphire plants were starting to grow over the newly placed sediment during the first summer.
As part of this project, extra research is being conduced at this site (by Earth Change, the UK Centre for Ecology and Hydrology (UKCEH) and Bangor University) to measure the nitrate absorption of saltmarsh as part of a wider nutrient neutrality programme being undertaken. The lessons learned will continue be captured and shared to understand how widely this approach can be applied.
Graphical information:
Location of SRDB drag box trial in Chicheter Harbour (map also shows current slatmarsh extent in orange)
Historic areas of marsh loss at the restoration site© ABPmer
Area of raised and restored habitats after Phase 1 © ABPmer
Drag box being trialed at West Itchenor in February 2023 (c) Land & Water Services Ltd