Beneficial use of dredged sediment
Demonstration or Pilot Project
Improve Water Quality
This project was undertaken to restrairean 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 moving it to the saltmarsh zone at the top of the shore using a new 'drag box'. This new drag box 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 to understand how the area performs. By July 2023 the findings were encouraging. The imported sediment was quite fluid but it stabilised quickly and then remained where it was placed. Some Samphire plants were starting to grow.
As part of this project, research is being conduced at this site (by Earth Change, CEH and Bangor University) to measure the nitrate absorption of saltmarsh as part of a wider nutrient neutrality programme being undertaken. The lessons learned will continues be captured and shared to understand how widely this approach can be applied.