Intertidal Surveys Adjacent to Langstone Village

Investigating the feasibility of restoring saltmarsh habitat to the east of Langstone Village, Chichester Harbour

Coastal Partners is currently investigating the feasibility of restoring an area of degraded saltmarsh habitat between Langstone Village and Warblington, within Chichester Harbour. This location historically supported a healthy saltmarsh ecosystem, but this has been lost over time due to a range of environmental pressures. Saltmarsh restoration involves the raising of the foreshore (mudflat) levels to an elevation that is suitable for saltmarsh plants to grow. This can be achieved by using clean sediments that have been dredged elsewhere within the harbour to maintain navigation channels and marinas. Reuse of the dredged sediments in this way is referred to as the Beneficial Use of Dredged Sediment (BUDS), as the sediment is reused for a wider environmental benefit, rather than being dumped outside of the harbour and lost from the system. The map below illustrates the location of the potential saltmarsh restoration area we are investigating:

On average, it is estimated that 2.54 hectares of saltmarsh are being lost within Chichester Harbour every year due to various pressures including sea level rise, coastal squeeze, lack of sediment supply and water quality issues. Saltmarsh provides many environmental benefits, including water quality improvements, carbon capture, removal of nitrates, feeding and roosting habitat for birds and nursery grounds for fish. It can also function as a natural flood and coastal defence, helping to dissipate wave energy and protect the intertidal foreshore. With partners, we are therefore investigating options to restore and recreate saltmarsh around Chichester Harbour as part of a suite of measures to reverse the environmental declines. The photo below illustrates healthy saltmarsh at Chidham, within Chichester Harbour:

As part of our feasibility investigations, Coastal Partners commissioned specialist consultancy ‘Ocean Ecology Ltd’ to undertake surveys of the intertidal habitats between Langstone Village and Warblington between the 16^th and 20^th September 2024, to investigate their environmental quality. These surveys were undertaken, to help inform if restoration of the saltmarsh at this location could impact the existing intertidal benthos (invertebrates in the mudflats). This is to ensure there will not be an unacceptable, negative impact on them. Future saltmarsh restoration could follow a similar approach to the nearby saltmarsh restoration trial at West Itchenor (Saltmarsh Restoration Trial Project – West Itchenor - Chichester Harbour Conservancy), with both projects being linked to the Solent Seascape Project (Solent Seascape Project | Blue Marine Foundation).

The intertidal survey samples have been analysed and the results have been written up. The survey technical report is available to view in the related information box. In summary, the survey found that the intertidal sediments in the area are broadly comprised of two main habitat types. On the upper shore, the habitat is dominated by coarse / gravelly sediments. The very upper shore comprises highly mobile pebbles, cobbles and gravels, which are subject to high degrees of drying between tides and few species are able to withstand and survive in these conditions. Just below this strandline, there is a gravelly mud habitat colonised by polychaetes (worms), the mud snail Peringia ulvae and the common cockle Cerastoderma edule.

On the mid- and lower shore, the habitat is predominantly a soft mud and fine sand community of variable salinity conditions, which is typical at the head of estuaries. Species living within this habitat include polychaetes (worms), the mud snail and the Baltic clam Macoma balthica.

The survey also mapped the existing extent of the degraded saltmarsh within the survey area, which we will use for reference in future monitoring to understand how the restoration works are progressing.

The survey noted that much of the study area was covered in thick opportunistic green macroalgae (seaweed), which smothers the underlying habitats. 

During the survey, sediment samples were also collected for chemical analysis to check for any potential heavy metal or hydrocarbon contamination. All the samples tested were below guideline levels at which adverse biological effects frequently occur, although there were some slightly elevated hydrocarbon levels in the west and east of the survey area, the source of which is currently unknown.

All the intertidal sediment habitat types recorded within the survey area are common and widespread within Chichester Harbour. The mudflat habitats are characteristic of the estuarine environment with highly fluctuating conditions including resuspension and deposition of sediments. These habitats by their nature have a low sensitivity and high recoverability to smothering.

The survey results have been shared with Natural England, who having had regard to the report, are “in principle supportive of a beneficial use trial at Langstone Village, Chichester Harbour.” 

Following receipt of these survey results and the ‘in principle support’ from Natural England, Coastal Partners will now plan out the next steps to progressing saltmarsh restoration at this location. We will keep this webpage updated with latest developments, and there may be future opportunity to support us in delivering this restoration project.

For any queries relating to this survey, please contact coastal.team@havant.gov.uk.