Historic monument set to be preserved with work to improve water quality of Hilsea moat to begin next week
Work to improve the water quality of Hilsea moat is set to start this week - including work to preserve the historic monument.
The North Portsea Coastal Scheme, which is creating new sea defences in Ports Creek, is celebrating a major milestone after additional dedicated environmental funding secured for 2025/26.
The funding will enable a wide range of improvements of the adjacent Hilsea moat in Foxes Forest that go far beyond flood protection.
Part of the historic Hilsea Lines fortifications, the moat is a vital green corridor supporting wetlands, reed beds, and woodland. However, it faces environmental challenges including algal blooms, silt build-up, and fluctuating salinity which can be deadly to the animals inhabiting these moats.
To address these issues, work beginning this week will include dredging to restore water depth and reduce temperature and salinity variations; placing reedbeds to trap nutrients; and carrying out marginal edging to hold dredged material whilst restoring eroded moat banks to their original form. This will also provide space for additional planting and refuges for fish and eels.
Works include:
- Water quality improvements
- Preservation of historic moats
- Habitat creation such as saltmarsh at intertidal zones
- Biodiversity improvements aligned with sustainable flood risk management
Amy Conway, project delivery manager said: “This is a shining example of how we can protect our heritage and restore nature all at once whilst delivering a future proof flood defence scheme.
“The area around Hilsea Lines is a hidden gem in Portsmouth, and our work, together with these improvements will help it thrive for generations to come - benefiting wildlife, residents, and the wider environment.”
Dredging starts this week and all moat improvement work is scheduled for completion by the end of 2025. Specialist plant, including an amphibious excavator, will work from inside the existing site boundary, so no extra path closures will be needed.
The initial dredging will disturb some long‑settled silt and may produce a temporary odour; this will disperse naturally and is not a cause for concern.
All works are being delivered in collaboration with Historic England. Scheduled Monument Consent has been granted for delivery of the coastal defence scheme and moat improvement works.
These enhancements are in addition to those being incorporated across the flood defence scheme, including a heritage interpretation strategy, bird boxes, bat boxes, kingfisher tunnels, beetle loggeries, and wildflower planting.