Benefical use of Dredgings (BuDS)

Dredge routes and disposal sites in the Solent © Dredge Sediment Resource Data Platform

There is a strong desire amongst Solent Forum members to find solutions to the many barriers which are preventing the effective use of dredged material to augment Solent intertidal sites and provide other benefits associated with restoration work (especially enhanced coastal protection). To find these solutions, in 2017 the Solent Forum convened a project working group of interested parties and initiated the BuDS Solent project. This project ran from 2017 to 2024. A final report provides a summary of the work that was undertaken. One final outcome of the process, was that unfortunately, the MMO were unable to proceed with the Marine Licence application. The concern was not with the activity itself but the practicalities of overseeing the multiple conditions and monitoring commitments which would have accompanied such a consent. The Solent Forum are not in a position to lead such ongoing commitment and on this basis withdrew the application, this means that the application can be taken forward by others in the future as this type of work evolves.

The project group will now look for new opportunities in the Solent and will next meet in March 2025 to look at the potential barriers in more detail and how to support small scale BuDS projects in the Solent. The Group will be facilitated by the Solent Forum.

BuDS Projects in the Solent

Lymington Harbour

Following several successful trials, since 2014 Lymington Harbour Commission has been placing up to 10,000 tonnes of sediment dredged from the harbour each year within a bay at the exposed seaward edge of the saltmarsh. The purpose was to create a sacrificial reef that will shelter the marsh behind from wind wave action and provide a source of sediment to ‘feed’ the marsh in the immediate vicinity. By August 2023 surveys showed that an area of mud of around 17,000m² had been raised by around 1.5m in height and its presence was slowing down erosion of the marsh behind.

While the technique described above has been successful at reducing erosion to the saltmarsh behind, the barges cannot get mud high enough in the tidal frame for new saltmarsh to grow. LHC worked with partners Land & Water / Earth Change, a marine contractor specialising in environmental enhancement projects, and Hampshire and Isle of Wight Wildlife Trust to trial a new technique to move a significant quantity of the previously placed and consolidated sediment higher up the tidal frame onto adjacent lower lying areas of decaying saltmarsh. The aim is to raise the trial area to the same level as supports the surrounding healthy high marsh to encourage new high marsh growth.

In December 2023, the Marine Management Organisation granted Lymington Harbour Commission a ten-year licence to trial new techniques and in 2024 the Environment Agency awarded Lymington Harbour grant funding from the DEFRA Water Improvement Fund to trial the new technique in August and September 2024. While the trial did not move as much sediment as was hoped due to difficult ground conditions contributing to equipment issues, and an unseasonably windy period, the technique showed considerable promise and a number of lessons were learned that will improve results for future schemes. The trial area will now be monitored until autumn 2025 and a report of the findings will be published in due course. Subsequent phases will be dependent on new grant funding awards.

Restoring Estuarine and Coastal Habitats with Dredged Sediment Handbook

This handbook is a practical guide for those interested in beneficially using dredged sediment for estuarine and coastal habitat restoration. It has been written with a broad audience in mind, not just specialists in the field. It is hoped that it will be of value for a range of individuals and organisations including policy makers, nature conservation bodies, local communities or anyone interested, or involved in, dredging, coastal management and ecosystem restoration. Page 11 of the handbook sets out the current barriers to beneficial use.

Dredge Sediment Resource Data Platform

This mapping platform was produced for the UK Beneficial Use Working Group (BUWG). It was created to help identify where dredged sediment can be used beneficially (e.g. for shoreline adaptation, flood protection and/or coastal habitat restoration). To achieve this, this platform collates the best available data and maps to answer the following questions:

Where and how does dredging and dredge sediment disposal take place in the UK;
Where could this sediment be beneficially used (esp. from maintenance activities); and
What issues need to be considered for beneficial use projects at any given location.

This ‘data-viewer’ also includes links to useful resources (e.g. guidance documents, case example websites). This information was brought together to enhance collaboration and communication between partnerships that want to use the dredge sediment resource beneficially., dredging specialists and organisations which regulate and advise on this sector.

Nab Tower

The Nab Tower is currently the main dredge disposal site in the Solent (indigo box in the map above). It is 11.5km from the coast. Recent quantities of disposed dredgings are shown below (source: Dredge Sediment Resource Data Platform).

Dry Tonnage (2020) 59,028.3, Metric Wet Tonnage (2020) 129,565.0
Dry Tonnage (2021) 663,392.9, Metric Wet Tonnage (2021) 1,590,468.5
Dry Tonnage (2022) 370,358.4, Metric Wet Tonnage (2022) 829,146.9
Total Dry Tonnage (2012-2022) 7,421,821.1, Total Metric Wet Tonnage (2012-2022) 15,576,050.6

There is a much smaller disposal site at the Needles (yellow box in the map), the total Dry Tonnage for 2012-2022 was 5,834.3 and the total Metric Wet Tonnage for 2012-2022 was 10,829.0 (source: Dredge Sediment Resource Data Platform).