Hook Lake Position Statement by Coastal Partners

Position Statement – Coastal Management of Hook Lake

This 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.

1. 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.

2. 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 December 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.

3. Partner Responsibilities

This section identifies the key partners and their responsibilities in relation to Hook Lake.

Fareham Borough Council

Fareham Borough Council (FBC) is a Risk Management Authority (RMA) and has permissive powers to undertake works (where there is a wider public benefit, clear economic benefit and an achievable solution) under The Coast Protection Act 1949 and Land Drainage Act 1991. These are permissive powers and not a legal obligation or responsibility on the Council to undertake any works (maintenance or new defences) to protect property from flooding or erosion. Coastal Partners provide the coastal engineering service to FBC, acting on behalf of the RMA.

Where FBC is the asset owner, they have a responsibility to manage health and safety risks effectively. FBC do not own any assets at Hook Lake.

Hampshire County Council

Hampshire County Council (HCC) as landowner, has ultimate responsibility for protecting their own property from flooding and erosion, but must act within statutory planning regulations and other applicable legislation Where accessible to the public, landowners also have a legal duty of care to maintain public safety under the Occupiers Liability Act.

HCC Countryside Services manage the Hook with Warsash Local Nature Reserve.

The existing embankment at Hook Lake is predominantly on land owned by HCC and to date this embankment has been maintained by the Environment Agency.

There is a public footpath along the top of the embankment, for which HCC, as the Public Rights of Way (PROW) Authority, is responsible for maintenance. The Countryside Services department have most recently repaired the footpath surface after the embankment was overtopped during Storm Barra (2021) and Eunice (2022).

Hampshire Highways

Hampshire Highways, as Hampshire County Council’s highway authority, are responsible for the highway assets including Hook Park Road and the road bridge which crosses Hook Stream. These assets are managed within their Highway Maintenance Management Policy and Strategy and Highway Maintenance Management Plan (HMMP). More information is here: https://www.hants.gov.uk/transport/roadmaintenance/highwaysassets

Environment Agency

The Environment Agency (EA) is responsible for the strategic overview of the management of all sources of flooding and coastal erosion in England. They are tasked with administering FCERM GiA on behalf of DEFRA. They are a RMA and have permissive powers to undertake defence works (where there is a wider public benefit, clear economic benefit and an achievable solution), but there is no legal obligation for the EA to undertake any works to protect property from flooding or erosion.

Inspection and maintenance of the Hook Lake embankment and sluice, as a water control structure, currently sits with the EA who inspect and maintain the assets. Inspections are undertaken each year, leading to minor works such as grass cutting and outfall maintenance. Significant works would require economic justification which is more challenging in the absence of residential properties at direct flood risk. Small scale emergency works may be justifiable. If at

some point in the future the EA decide to withdraw maintenance of the embankment and sluice at Hook Lake, consultation would take place with key parties before maintenance ceases.

The HCRP is a strategic programme run by the EA which seeks to replace habitats that are lost due to coastal squeeze or tidal inundation effects that arise from the management of coastal defences. Coastal Partners works with the EA to co-ordinate the HCRP in the Solent and South Downs area, between Hurst Spit in Hampshire to Beachy Head in East Sussex, including the north coast of the Isle of Wight

The HCRP reviews, implements, and monitors habitat compensation targets arising from the relevant Shoreline Management Plans and meeting those targets is a legal requirement. Since 2010 there have been several habitat schemes already completed in the Solent and South Downs area, however, there is still an urgent need for habitat compensation to meet the outstanding requirements for the area, which was a key driver for the Hook Lake Coastal management Study.

Private Landowners / asset owners

Private Landowners have ultimate responsibility for protecting their own property from flooding and erosion but must act within statutory planning regulations and other applicable legislation e.g., Coast Protection Consent.

Coastal Partners have compiled practical advice about management of flood risk here: https://coastalpartners.org.uk/protecting-against-flooding

4. Impact of Storm Pierrick April 2024

This section acknowledges the impact of exceptional high tides overnight into 9 April 2024. The local Hamble tide gauge recorded a level of 5.87mCD. The crest of the embankment which forms the footpath around Hook Lake at its lowest point is 5.25mCD so there was significant overtopping. Water leaving the site on the low tide led to the collapse of the upper section of masonry wall along a ~40m section essentially reducing the crest height which was roughly at Highest Astronomical Tide level (5mCD), now reduced to footpath level (4.8mCD) and lower in some places.

Whilst the outer wall has collapsed down to the sheet pile base, the embankment behind remains relatively high and dry (coming into a relatively settled period over the 2024 spring/summer).

The upper footpath in the location of the collapsed wall is between 4.8m-4.9mCD, which is slightly above Mean High Water Spring therefore would not expect regular tidal flooding unless a breach is established through the earth embankment. The upper footpath remains closed by Hampshire County Council.

This damaged area will be vulnerable to highest tides and any storm surges ahead during this or any future autumn/winter period.

HCC and the EA are working together to investigate next steps.

5. Potential future management pathways

A pathway approach identifies the management decisions that can be taken now and those that may be taken in the future. It is a flexible approach which allows decision makers to plan for and prioritise future actions in line with changing circumstances over time. Decision points are included which could trigger a decision to change to a different action or pathway.

The potential management pathways for Hook Lake are shown below. The current management approach is highlighted in blue.

Within this section, the current management pathway and three potential alternative future management pathways are presented for the Hook Lake site, alongside the resulting impacts and risks highlighted for each

CURRENT PATHWAY: Action B then Action A

Continue maintaining the embankment until unsustainable.

Via this pathway, HCC would continue to be responsible for the Hook with Warsash Local Nature Reserve and the footpath network, and the EA continue to maintain the main embankment until it is no longer cost effective to do so or defences reach the end of their lives.

Under this current pathway the following impacts and risks within the Hook Lake site are expected over time:

Main Embankment

• The integrity of the embankment and sluice will be maintained until such a time that it is not technically or economically viable to continue to maintain, i.e., significant repairs or capital investment is required.

• The embankment will continue to hold back the sea all the time it is in place, however, sea water may wash over the defence during very high tides and during storm events. The frequency of these events will increase as sea levels rise.

• Increased overtopping of the defence will result in more frequent maintenance requirements and increased costs.

• Even with maintenance, an exceptional event could lead to failure and breach of the embankment, with permanent inundation of seawater into the site and loss of the footpath on the embankment.

Hook Park Road Bridge

• During normal tides and with the main embankment in situ, there is a low risk of flooding to Hook Park Road bridge.

• During exceptional tides Hook Park Road bridge would flood, like that experienced on the 7 December 2021 during Storm Barra, and 9 April 2024 during Storm Pierrick. This would be periodic and align with high tides.

• In the event of an uncontrolled breach, Hook Park Road bridge would flood regularly.

Footpath Network

• During normal tides and with the main embankment in situ, there is a low risk of flooding to the footpath network.

• During exceptional tides the main embankment footpath would flood.

• In the event of an uncontrolled breach, the main embankment footpath would be lost, the rest of the footpaths would flood regularly, and the integrity of the network lost.

Freshwater Habitats

• During normal tides and with the embankment in situ, the freshwater habitats within the nature reserve would be unaffected. There may be sea water intrusion during exceptional tidal events, but this would drain out at low tide.

• In the event of an uncontrolled breach, freshwater habitats would be inundated with sea water and habitats will transition over time to intertidal habitat.

Properties

• During normal tides and with the embankment in situ there is a low risk of flooding to properties.

• During exceptional tides there is a low risk of flooding to properties, unless this coincides with a fluvial / high rainfall (surface water) event.

• In the event of an uncontrolled breach, some properties in Lower Spinney Road and Fleet End Road may be at increased flood risk over time if climate change and sea level rise increase as predicted. Some gardens may experience flooding during exceptional tides.

ALTERNATIVE PATHWAY 1: Action A

No Active Management of Defences

Via this potential alternative pathway, HCC would continue to be responsible for the Hook with Warsash Local Nature Reserve and the footpath network, but EA withdraw maintenance of the main embankment or sluice Under this potential scenario the following impacts and risks to Hook Lake are expected:

Main Embankment

• In the absence of maintenance, the embankment would continue to overtop and cause scour and backslope erosion more frequently. Any damage would not be repaired leading to a rapid overall decline in condition.

• An exceptional event would lead to failure and breach of the embankment, with permanent inundation of seawater into the site and loss of the footpath on the embankment.

Hook Park Road Bridge

• During normal tides and with the main embankment in situ, there is a low risk of flooding to Hook Park Bridge.

• During exceptional tides Hook Park Road bridge would flood, like that experienced on the 7 December 2021 during Storm Barra, and 9 April 2024 during Storm Pierrick

• At a future point in time, when the defences fail and an uncontrolled breach occurs, Hook Park Road bridge would flood regularly.

Footpath Network

• During normal tides and with the main embankment in situ, there is a low risk of flooding to the footpath network.

• During exceptional tides the main embankment footpath would flood.

• At a future point in time, when the defences fail and an uncontrolled breach occurs, the main embankment footpath would be lost, the rest of the footpaths would flood regularly, and the integrity of the network lost.

Freshwater Habitats

• At a future point in time, when the defences fail and an uncontrolled breach occurs, freshwater habitats would be inundated with sea water and habitats will transition over time to intertidal habitat.

Properties

• During normal tides and with the embankment in situ there is a low risk of flooding to properties. Some gardens may experience flooding during exceptional tides.

• During exceptional tides there is a low risk of flooding to properties, unless this coincides with a fluvial event.

• At a future point in time, when the defences fail and an uncontrolled breach occurs, some properties in Lower Spinney Road and Fleet End Road may be at increased flood risk over time if climate change and sea level rise increase as predicted.

ALTERNATIVE PATHWAY 2: Action B, then Action C, then Action A Mitigation

with No Active management of Defences

Via this potential alternative pathway, HCC would continue to be responsible for the Hook with Warsash Local Nature Reserve and the footpath network, and the EA continue to maintain the main embankment until it’s no longer cost effective to do so or defences reach the end of their lives.

Under this potential scenario, proactive mitigation measures are put in place to mitigate for increased flood risk to the bridge, footpaths and some properties. Once in place, there would be no further active management of defences This is subject to obtaining the necessary funding, licencing and consents.

Under this pathway the following impacts and risks within the Hook Lake site are expected over time:

Main Embankment

• The integrity of the embankment and sluice will be maintained until such a time that it is not technically possible to continue to maintain, i.e. significant repairs or a new defence is required.

• Increased overtopping of the defence will result in more frequent maintenance requirements and increased costs.

• Ideally, mitigation measures would be in place before the embankment fails, however, even with maintenance, an exceptional event could lead to failure and breach of the embankment, with permanent inundation of seawater into the site and loss of the footpath on the embankment.

Hook Park Road Bridge

• During normal tides and with the main embankment in situ, there is a low risk of flooding to Hook Park Road bridge.

• During exceptional tides Hook Park Road bridge would flood, like that experienced on the 7 December 2021 during Storm Barra, and 9 April 2024 during Storm Pierrick.

• Mitigation measures to maintain access to Hook Park would mitigate for increased flood risk to the bridge

Footpath Network

• During normal tides and with the main embankment in situ, there is a low risk of flooding to the footpath network.

• During exceptional tides the main embankment footpath would flood.

• Mitigation measures to relocate footpaths would help maintain the integrity of the network.

Freshwater Habitats

• In the event of an uncontrolled breach, freshwater habitats would be inundated with sea water and habitats will transition over time to intertidal habitat.

Properties

• During normal tides and with the embankment in situ there is a low risk of flooding to properties.

• During exceptional tides there is a low risk of flooding to properties, unless this coincides with a fluvial / high rainfall (surface water) event.

• If mitigation measures are in place, flood risk to some properties in Lower Spinney Road and Fleet End Road would be reduced.

ALTERNATIVE PATHWAY 3: Action B, then Action C, then Action D, then Action A Actively Breach the Embankment for Habitat Creation

Proactive mitigation measures are put in place to mitigate for increased flood risk to the bridge, footpaths and some properties (as deemed necessary) and to compensate for freshwater habitat losses.

Once in place, breach the embankment to create intertidal habitat in a managed way, then revert to no active management of defences.

This is subject to obtaining the necessary funding, licencing and consents.

Under this potential pathway the following impacts and risks within the Hook Lake site are expected over time:

Main Embankment

• The integrity of the embankment and sluice would be maintained until such a time that it is not technically possible to continue to maintain, i.e., significant repairs or a new defence is required.

• A breach could be made in the main embankment to allow seawater into the site.

• Once it has reached the end of its design life the rest of the main embankment will fail.

Hook Park Road Bridge

• During normal tides and with the main embankment in situ, there is a low risk of flooding to Hook Park Road bridge.

• During exceptional tides Hook Park Road bridge would flood, like that experienced on the 7 December 2021 during Storm Barra, and 9 April 2024 during Storm Pierrick

• Mitigation measures to maintain access to Hook Park would mitigate for increased flood risk to the bridge.

Footpath Network

• During normal tides and with the main embankment in situ, there is a low risk of flooding to the footpath network.

• During exceptional tides the main embankment footpath would flood.

• Mitigation measures to relocate footpaths would help maintain the integrity of the network.

• Opportunities to enhance the current footpath provision as part of a scheme.

Freshwater Habitats

• With a breach, freshwater habitats would be inundated with sea water in a managed way.

• 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).

• Freshwater habitat lost would be compensated for with creation of new freshwater habitats elsewhere.

• Opportunities to enhance habitats further, for example with bird islands, scrapes and lagoons, beneficial use of dredged sediments, enhanced woodland management, removal of non-native invasive species, creation of reptile hibernacula and enhancement of bat roosting, foraging and commuting habitat.

Properties

• During normal tides and with the embankment in situ there is a low risk of flooding to properties.

• During exceptional tides there is a low risk of flooding to properties, unless this coincides with a fluvial / high rainfall (surface water) event.

• Mitigation measures would be included as part of the scheme as necessary to reduce flood risk to some properties in Lower Spinney Road and Fleet End Road

6. Addressing future risks and uncertainties

Coastal Partners will continue in their role to advocate focused discussions with partners at both local and national levels, on the key challenges and cost uncertainties identified through the study

The outcome of these discussions and availability of funding will affect the viability of the scheme and inform the decision at a later date to either progress the scheme to the next stage of detailed design, licences and consents, or to not progress the scheme any further Where there are significant developments, these will be communicated with key Stakeholders as appropriate.

7. Further Information

For further information please visit:

Hook Lake Coastal Management Study: https://coastalpartners.org.uk/project/hook-lakecoastal-management-study

Habitat Compensation and Restoration Programme: https://southerncoastalgroupscopac.org.uk/rhcp/

Hook with Warsash Local Nature Reserve: https://www.hants.gov.uk/thingstodo/countryside/finder/hookwarsash

Long term flood risk: https://www.gov.uk/check-long-term-flood-risk

Managing flood risk: https://check-long-term-flood-risk.service.gov.uk/managing-flood-risk

When the Environment Agency stops maintenance: https://www.gov.uk/guidance/flood-andsea-defences-when-maintenance-stops