At the coast, in areas where land meets the sea, intertidal habitats form. In the Solent, these include mudflats and sandflats, saltmarsh, rocky shores and seagrass beds. These habitats are both home to a range of flora and fauna, but also a source of food for others. The Solent coastline is facing significant pressure from rising sea levels, more frequent and bigger storms, and increased flood and erosion risk. Important intertidal habitats are slowly being lost as they are squeezed against sea defences. Creating new places for coastal habitats and wildlife to thrive is essential to ensure that they are resilient to the challenges of climate change. It will also ensure that local communities can continue to enjoy our treasured coastlines for many years to come.

The Hook with Warsash Nature Reserve, located at the entrance to the River Hamble within the Solent, hosts a variety of coastal habitats which provide shelter for overwintering and breeding birds each year. The coastal footpaths that intertwine the reserve are very popular with the local community and visitors alike. Enabling the tide to return to areas which were historically tidal could enable generation of valuable intertidal habitats.  

Updated: October 2024

Hook Lake Coastal Management Study

Why?

As sea level rises, important intertidal habitats along the coast will be lost as they are constrained by hard sea defences and are unable to migrate landwards as they would naturally do. Replacing and recreating the habitat that is lost (due to implementation of new coastal defence schemes) is a legal requirement that will help to offset these losses both today and in the future from new defence schemes. Without a clear plan for compensatory habitat in place for the future, regulators may be unable to consent any new flood and coastal erosion risk management (FCERM) works in the Solent.

The Habitat Compensation and Restoration Programme (HCRP) is the Government’s agreed mechanism for delivering strategic habitat compensation for FCERM. Through the HCRP, Hook Lake was identified as a potential site to create new intertidal habitat as it has the required characteristics for intertidal habitat to thrive and it is already managed as a nature reserve.

The potential for intertidal habitat creation at Hook Lake was also identified in the both the North Solent Shoreline Management Plan (2010) and the River Hamble to Portchester Coastal Strategy (2016). The Hook Lake Coastal Management Study built on the work of these earlier plans to understand the potential of the site in more detail, and how it could be managed sustainably in the future.

How?

Coastal Partners as part of Fareham Borough Council, supported by engineering consultancy Binnies, worked in partnership with Hampshire County Council, who own and manage Hook Lake as a nature reserve, the Environment Agency and the River Hamble Harbour Authority to deliver this coastal management study.

As this project looked to fulfil a legal requirement to create new habitat, the Hook Lake Coastal Management Study was entirely funded by Government through Defra FCERM Grant in Aid (GiA).

What?

The Coastal Management Study was the first stage in the delivery of a habitat creation scheme at Hook Lake. The two-year study aimed to better understand the site, explore the potential for creating new intertidal habitats and develop preliminary designs for a scheme.

The study looked to identify the most cost efficient and effective way of creating new intertidal habitat. Although this project looks to fulfil a legal requirement, strict funding rules means there is no guarantee a future scheme here would secure funding from the UK Government.

Key Findings of the Study

Commencing in 2021, the study has allowed us to better understand the site in relation to the existing environment (ecology and heritage), current defence condition, the topography of the site, contamination risk and existing and future flood risk. Through experiencing two significant storm events during development of the study (Storm Barra in Decemeber 2021 and Storm Eunice in February 2022), we also now have a greater understanding of how the site responds and what is at risk during these events. This understanding has been built upon further after the study with the occurrence of Storm Pierrick in 2024. Through the study we now know that:

• The existing habitats within the site are of high value and include coastal grazing marsh, saltmarsh, coastal vegetated shingle, lowland meadows, reedbeds and wet woodland. These habitats support a variety of wildlife including protected species such as breeding and over-wintering birds, reptiles, water voles, bats and badgers.
• Existing defences have been graded as poor, have short residual lives of less than 10 years, and offer a low standard of protection against flooding.
• The main embankment already regularly overtops and suffers erosion on its rear face.
• The site has many of the characteristics which are needed for the development of a successful intertidal habitat creation scheme.
• The Hook Park Road bridge and the footpath network are at flood risk due to extreme tides now and in the future with sea level rise, irrespective of whether a habitat creation scheme is progressed or not. This is dependent on the condition of the main embankment.
• Letting sea water back into the Hook Lake site would actively increase flood risk to Hook Park Road bridge at an accelerated pace (without mitigation).
• Continued accessibility and maintaining the footpath network is very important to the community.

With key partners we have explored the potential for creating new intertidal habitats at Hook Lake, through option appraisal and flood modelling. As a result, a technically feasible option was identified, and outline designs generated for a scheme that has the potential to create 45ha of intertidal habitats (saltmarsh and mudflat) in the short term and up to 60ha of intertidal habitat in the longer term (100 years).

Challenges

In addition to establishing that a technically feasible scheme was possible, the study has also identified some key challenges that could significantly impact the financial viability of a scheme at Hook Lake:

• Active creation of new intertidal habitats in an area which is already heavily environmentally designated for its freshwater habitats would require compensation (re-creation elsewhere) of the existing habitats lost before a scheme can be implemented. New freshwater habitat already created at Manor House Farm in the Lower Test Valley would provide some compensation needs for Hook Lake, but it is not enough to compensate for all losses at Hook Lake. 
• New Biodiversity Net Gain (BNG) Regulations for projects have become a legal requirement, but it is unclear from the published guidance as to how this should be applied to habitat compensation schemes. If BNG is required for habitat compensation schemes, then at a minimum, an additional 10% of biodiversity gain would need to be created; this carries a high cost.
• Actively letting sea water back into the site would accelerate flood risk to Hook Park Road bridge which would be vulnerable during normal tides (and not just extreme tides). Any scheme implemented here would therefore need to mitigate for the resulting increase in flood risk, by for example, raising the bridge.

Questions are now being raised at a National level with Natural England and the Environment Agency to clarify how habitat compensation and BNG requirements should be applied to habitat creation schemes, and to ask if there is a financial limit set on how much funding would be made available to deliver a legally required habitat creation scheme.

At the same time, discussions need to continue with HCC as landowner with respect to ongoing risks and with Hampshire Highways to look at and cost mitigation options for the road bridge, with or without a scheme.

Each of these challenges would need to be addressed, clarified and overcome in order for the project to progress further. Therefore, whilst the study stage is complete, there is now a need to pause. This is an important step we need to take to enable focused discussions with partners at both local and national levels, on the key challenges and cost uncertainties identified through the study.

Position Statement – Coastal Management of Hook Lake 

A position statement has been prepared by Coastal Partners following the completion of the Hook Lake Coastal Management Study. It aims to set out the findings of the Study, the current roles and responsibilities of key partners in relation to the site, current management, potential future scenarios for the management of the site, alongside the residual risks and next steps.  

You can view this document online.