Chichester Harbour Area of Outstanding Natural Beauty

CHICHESTER HARBOUR One of the AONB Family

Sustainable Shorelines General Guidance First Edition

Preface

Chichester Harbour covers 29 square miles, made up of 53 miles of shoreline, extensive saltmarshes and mudflats, surrounded by farmland and historic settlements. It is a landscape of national importance, recognised by the Area of Outstanding Natural Beauty (AONB) designation awarded in 1964. This unique landscape provides a wealth of habitats for wildlife, in particular migratory and overwintering birds, for which it has the highest national and international levels of protection.

Historically, the natural shoreline of the Harbour is a wooded fringe of coastal oaks, with extensive saltmarshes in front, leading to mudflats and eventually the sub-tidal channels. 43% of the AONB is fully submerged at high tide. Chichester Harbour is the largest natural estuary in south east England.

Over the centuries, shoreline defences have been built to protect the farmland and settlements in the Harbour. These were constructed in a variety of styles and materials, and currently make-up approximately two-thirds of the Harbour’s shoreline. Most of the shoreline defences in Chichester Harbour are privately owned, although significant stretches are publicly owned and maintained by the relevant authorities. All landowners have a shared responsibility to ensure that the natural character of the AONB is looked after.

The overall aim of this General Guidance is to provide an introduction to sustainable shoreline management in Chichester Harbour, respecting the range of environmental and cultural designations. It is therefore a starting point for somebody considering shoreline defences and should prompt further thought and discussion with Chichester Harbour Conservancy and other organisations at the earliest opportunity – ideally in plenty of time before a planning application is submitted.

The General Guidance is not designed to be a catalogue of defences from which readers can choose their preferred solution for their own property.

Contents

1.0 Context...... 6 1.1 Chichester Harbour – A Protected Area...... 7 1.2 Sea Level Rise and Coastal Squeeze...... 8

2.0 Policy and Consents Framework...... 10 2.1 Sustainable Management of the Shoreline...... 11 2.2 North Solent Shoreline Management Plan...... 12

3.0 Decision-Making Guidance...... 14 3.1 Choosing a Shoreline Defence...... 15 3.2 Strategic Polices...... 15

4.0 Typical Plan Layouts...... 18 4.1 Shoreline Defence Options...... 19 4.2 Hold the Line along the Existing Line...... 20 4.3 Hold the Line using Imported Material...... 21 4.4 Hold the Line using Groynes...... 22 4.5 Hold the Line using Secondary Defence...... 23 4.6 Managed Realignment with Partial use of Existing Defence...... 24 4.7 Managed Realignment with No Re-use of Existing Defence...... 25

5.0 Typical Cross-Sections and Construction Details...... 26 5.1 Types of Defence...... 27 5.2 Surface Layer Structure...... 28 5.3 Bed Formation...... 31 5.4 Embankment Formation...... 33 5.5 Gravity Structure...... 35 5.6 Piled Structure...... 38

6.0 Further Information...... 40 6.1 Glossary...... 40 6.2 Useful websites...... 42 1.0 Context

Designations in Chichester Harbour

Ramsar Site Wetlands are among the most diverse and productive ecosystems. Chichester and Langstone Harbours were recognised as a wetland of international importance when they were designated as a Ramsar Site in 1987, under the Ramsar Convention. They regularly holds more than 20,000 wildfowl and waders in winter. Worldwide Worldwide Designations

Special Area of A Special Area of Conservation (SAC) is a site designated under the Habitats Conservation Directive. These sites, together with Special Protection Areas, are called Natura

2000 sites and they are internationally important for threatened habitats and species. The Solent Maritime SAC was designated in 1994.

Special Protection A Special Protection Area (SPA) is a site designated under the Birds Directive. European

Designations Area These sites, together with Special Areas of Conservation, are called Natura sites and they are internationally important for threatened habitats and species. Chichester and Langstone Harbours SPA was designated in 1979.

Area of Outstanding An Area of Outstanding Natural Beauty (AONB) is a landscape which is Natural Beauty considered so precious that it is protected for the nation. The criteria for designating an AONB include valuable wildlife, habitats, geology and heritage, as well as scenic views. Chichester Harbour was designated as an AONB in 1964. The land and seascape are characterised by open water, intertidal mud

and saltmarshes, framed by coastal oak woodlands and backed by the South Downs National Park. The designation affords great protection within the national planning system. National Designations Site of Special Chichester Harbour was designated as a Site of Special Scientific Interest (SSSI) Scientific Interest in 1970 because it was considered to be of special interest by virtue of its fauna, flora, geological or physiographical / geomorphological features and the extensive intertidal mudflats, saltmarsh, shingle spits and islands.

Conservation Area Conservation Areas protect notable environmental and historical places of interest. There are 12 Conservation Areas in and around Chichester Harbour.

Local Nature Local Nature Reserves are particularly appropriate for educational, research Reserve or public information purposes. There are 9 Nature Reserves in and around Chichester Harbour.

Local Wildlife Site Local Wildlife Sites in West Sussex feature important habitats that complement

Local Local Nature Reserves and the Site of Special Scientific Interest. They are the equivalent of a Site of Importance for Nature Conservation, in Hampshire. There Designations are 16 Local Wildlife Sites in and around Chichester Harbour.

Site of Importance Sites of Importance for Nature Conservation (SINC) in Hampshire feature for Nature important habitats that complement Local Nature Reserves and the Site of Conservation Special Scientific Interest. They are the equivalent of Local Wildlife Sites in West Sussex. There are 47 SINCs in and around Chichester Harbour. 1.1 Chichester Harbour – A Protected Area

Chichester Harbour’s unique landscape and habitats Through the planning and consents process, measures are recognised by a range of national and international may be suggested to offset any potential harm caused by designations, affording it the highest level of protection. shoreline defences in the Harbour. These may include: The swathes of intertidal mudflats provide a rich food source for the 55,000 migrating birds that use the • Avoidance of works – there may be a case for not Harbour each year. defending or no longer defending the shoreline but instead allowing it to respond naturally to natural Area of Outstanding Natural Beauty (AONB) processes. designation confers protection on the landscape of Chichester Harbour recognising its national importance. • Type of works – making greater use of managed It has the same status in law as a National Park and retreat rather than hold the line, sloping rather than is recognised as a Category V Protected Area by the vertical structures, and ‘softer’ / natural materials IUCN, the International Union for the Conservation of rather than ‘harder’ / man-made materials. Nature. The Conservancy therefore expects the quality of planning, and any mitigation and compensation, to • Timing of works – this will require careful planning be proportionate with the national and international to avoid disruption to feeding migrating birds, status of this landscape. overwintering birds and summer breeding birds. There will be a limited window of opportunity A number of other designations help to protect the for construction works adjacent to the SPA/ natural and cultural environment of Chichester Harbour. SSSI boundary and advice is provided by Natural The combination of the Special Area of Conservation England. and Special Protection Area form part of the Natura 2000 network of nature protection areas in the • Mitigation and compensation for works – where European Union. shoreline defence works may cause a net loss of intertidal habitat in the SAC. In the first instance, Individually and collectively, these designations mean if new defences are replacing existing structures, that the Harbour’s environment must be given the these should remain within the existing footprint, highest regard by public authorities when making wherever possible. After that it may be a requirement development management decisions. Due care and that compensation habitat is provided elsewhere. consideration must be taken not to cause any damage to the protected areas or disturbance to the species It is worth noting that there are many more types of which use it. shoreline defences available than those covered in this document, which you may see in other coastal Chichester Harbour also holds a rich cultural heritage areas. Shoreline defences like floating breakwaters and with diverse evidence of continuous human occupation tyre bales can be successful. However, in an Area of since prehistoric times through to World War II. There Outstanding Natural Beauty, like Chichester Harbour, are four Scheduled Ancient Monuments either wholly or these solutions are highly unlikely to receive the partly within the AONB. necessary consents; therefore we have not included them in this General Guidance. In addition, the Historic Environment Record (HER) holds information on the location of 755 known find sites within the Harbour. The HER is held by Chichester District Council and Hampshire County Council, and should be considered as part of any shoreline defence proposal.

7 1.2 Sea Level Rise and Coastal Squeeze

Coastal Squeeze

8 The shoreline of Chichester Harbour is dynamic. It is will have an impact on the Harbour’s intertidal area a constantly changing environment driven by natural and shoreline, there is a strong policy and consents physical processes of wind, waves and tide. Erosion of framework in place to regulate this development and the coast can be unpredictable, with localised impacts. landowners are encouraged to consider alternatives to Shoreline defences can affect the physical processes replacing existing defences. by altering local conditions, and in some instances, displacing erosion from one location to another. As the sea level rises, the area of intertidal habitat will be reduced as the fixed defences prevent Between 1901 and 2010, global sea levels rose by movement inland. This is known as coastal squeeze, an estimated 19cm, with an average of about 1.7mm and as the illustration shows, if the defences are per year. However, between 1993 and 2010, sea not appropriate they will lead to a net loss of the levels rose by an estimated 3.2mm per year – almost Harbour’s internationally important saltmarshes and twice the long term average – indicating that sea mudflats. Coastal squeeze is a particular concern level rise is speeding up. The UKCP09 projections in Chichester Harbour. As the diagrams illustrate, indicate a likely further rise of between 18cm and when hard defences interfere with natural process 26cm by 2050, with the potential for a sharp increase the consequences can be stark. Over time, the upper thereafter depending on the success of the actions saltmarsh is literally ‘squeezed’ out since the habitat taken between now and then to try and slow these has nowhere to migrate to. However, it may be that rates down. If the interventions are ineffective, by the there is an overriding concern that properties or land end of the century sea level rise could be as high as require hard defences. In these cases where it is 82cm. Yet even relatively small increases in water level accepted that an adverse impact is unavoidable, it is will have an impact on coastal communities, habitats, important to mitigate the works as much as possible. and the species they support, across the flat, low-lying landscape of the Harbour. In the Solent, the Regional Habitat Creation Programme (RHCP) strategically delivers the creation of new coastal Environment Agency flood mapping suggests that and wetland habitats to replace those damaged or almost a third of the Harbour’s low-lying coastal land lost by flood or coastal defence works and sea-level may be at risk of flooding in the future. A number of rise. It is coordinated by the Environment Agency in other predicted impacts of climate change will affect partnership with Natural England, Local Authorities and the Harbour, including increased storminess, larger other organisations. The RHCP also takes into account waves, and higher winter rainfall. Already, anecdotally, the losses caused by coastal squeeze from the there is an increased frequency of storm events, continued maintenance of defences including existing which when combined with high tides, will contribute privately maintained defences. The programme works to flooding events. Sea level rise, together with through various mechanisms including land purchase deterioration of the existing defences over time, leads from willing landowners, or through agri-environment to demands from residents and business owners to schemes. Information can be obtained from the RHCP renew shoreline defences to protect property and land. team at the Environment Agency, or Natural England’s Given that any shoreline defence works undertaken coastal team.

9 2.0 Policy and Consents Framework 2.1 Sustainable Management of the Shoreline

Many policies regulate construction activity in the • To seek opportunities to adapt to the impacts of sensitive environment of Chichester Harbour. Proposals sea level rise on the landscape, access and nature for new defences, improvements to existing defences, or conservation interests of the AONB. removal of defences, require the applicant to obtain all relevant consents and permissions before carrying out The local planning authority will be able to provide any works. The Chichester Harbour AONB Management advice on whether any given project requires planning Plan (2014-2019) is a partnership document that sets permission. As well as the Chichester Harbour AONB out the policies to conserve and enhance the natural Management Plan, developments must adhere to environment. the National Planning Policy Framework, the National Planning Policy Guidance, the respective Local Plans The current Management Plan policies for Coastal for Havant Borough and Chichester District, and any Defence and Sea Level Rise are as follows: relevant Supplementary Planning Guidance.

• To ensure that responses to the impacts of sea level Construction works can involve repairing existing rise have full regard to the landscape, navigation, defences, constructing new defences and/or removing recreation and nature conservation interests of existing defences. For new works there are a number Chichester Harbour and balance the needs of of different types of structures to consider, which residents and businesses. act in different ways, all with various advantages and • To explore the potential impacts of climate change disadvantages. The construction of shoreline defences and sea level rise and provide advice to residents, in Chichester Harbour is tightly regulated, and a range businesses and users of the AONB. of permissions and consents are required before works can take place.

Planning permission The Local Planning Authority will consider the various impacts of your defences on the Harbour. Planning consent is required for construction and engineering works.

Marine Management The MMO will ensure that your defences adhere to the latest national marine planning policies. A marine Organisation (MMO) licence licence must be obtained for all construction works below mean high water springs.

Natural England consent Natural England will consider the potential impacts of your project on the conservation designations.

Environment Agency flood The Environment Agency will look to ensure that your works do not increase flood risk, damage flood defence consent defences, or harm the environment, fisheries or wildlife.

Chichester Harbour Chichester Harbour Conservancy will consider all aspects of the application, including any interference Conservancy works licence with public rights of navigation and other public rights. Under the direction of the Chichester Harbour Conservancy Act of 1971, the Conservancy retains the right to veto any works in the Harbour if it so pleases, even if other permissions and consents are in place.

11 2.2 North Solent Shoreline Management Plan

A Shoreline Management Plan (SMP) is a high-level, Chichester Harbour is divided in 19 different units and non-statutory, policy document setting out a framework three epochs: for future management of the coastline and coastal defences. It promotes management policies into the 22nd • 0-20 years century that will achieve long-term objectives without • 20-50 years committing future generations to unsustainable practices. • 50-100 years

The North Solent Shoreline Management Plan was The North Solent Shoreline Management Plan sets published in 2010. The strategy provides a framework policy over the next 100 years, looking beyond the that informs the statutory planning system since it is a lifespan of all coastal defence structures into a period material planning consideration. where the effects of climate change will have significant impacts on coastal management. Alterations to sea level, waves and tides and changing weather patterns were considered in this process.

12 North Solent Shoreline Management Plan (west to east)

Unit Start of Unit End of Unit Epoch 1 Epoch 2 Epoch 3 (0-20 Years) (20-50 years) (50-100 years) 5aHI05 Chichester Harbour Langstone Harbour HTL HTL HTL entrance (west) entrance (east) 5aHI04 Mengham Chichester Harbour HTL HTL HTL entrance (west) 5aHI03 Northney Farm Mengham HTL (NPFA) HTL (NPFA) HTL (NPFA) 5aHI02 Northney Farm HTL (NPFA) HTL (NPFA) HTL (NPFA)1 5aHI01 Langstone Bridge Northney Farm HTL HTL HTL 5a18 Wade Lane Southmoor Lane HTL HTL2 HTL2 5a17 Maisemore Gardens Wade Lane HTL HTL3 HTL3 5a16 Emsworth Yacht Haven Maisemore Gardens HTL HTL HTL 5a15 Wickor Point Emsworth Yacht Haven HTL HTL HTL 5a14 Marker Point Wickor Point HTL HTL HTL 5a13 Stanbury Point Marker Point HTL HTL HTL 5a12 Prinsted Stanbury Point HTL HTL HTL 5a11 Nutbourne Prinsted HTL HTL HTL 5a10 Nutbourne HTL (NPFA) HTL (NPFA) HTL (NPFA) 5a09 Chidham Point Nutbourne HTL (NPFA) HTL (NPFA) HTL (NPFA) 5a08 west of Cobnor Point Chidham Point MR HTL (NPFA) HTL (NPFA) 5a07 Fishbourne west of Cobnor Point HTL (NPFA)4 HTL (NPFA) HTL (NPFA) 5a06 Fishbourne HTL (NPFA) HTL (NPFA) HTL (NPFA) 5a05 Ella Nore Lane Fishbourne HTL (NPFA) HTL (NPFA) HTL (NPFA)5 5a04 Cakeham (inc. East Head) Ella Nore Lane) AM AM AM

Key AM Adaptive Management HTL Hold The Line MR Managed Realignment NPFA No Public Funding Available

¹ Further detailed studies are required which consider whether MR may occur at Northney Farm. ² Further detailed studies are required which consider whether MR may occur at Southmoor. ³ Further detailed studies are required which consider whether MR may occur at Conigar and Warblington. 4 Localised MR east Chidham. 5 Localised MR Horse Pond.

13 3.0 Decision Making Guidance 3.1 Choosing a Shoreline 3.2 Strategic Policies Defence

The development of an appropriate option should Chichester Harbour Conservancy recognises three not be undertaken in isolation. Consideration ways in which the shoreline can be managed. In order should be given to other nearby defences and preference, these are: wider ‘cause and effect’ implications on the Harbour. In developing an appropriate option, it is advisable to speak to Chichester Harbour 1 Conservancy and the Local Planning Authority at the earliest opportunity. No active intervention / adaptive management of an existing defence With a view to meeting the overall management Let nature take its course. No further maintenance or objectives of the Harbour, this section sets out the repair work is undertaken except to manage health various options in their order of preference following and safety at the site, allowing existing defences to the three staged approach to identifying an appropriate deteriorate safely over time until they are removed. option. The choice of shoreline defence will depend Adaptive management can result in a more gradual loss on the existing and adjacent defences, the degree of backshore and the continued evolution of a natural of exposure to wave action, the potential impact on dune habitat and land form. the local environment, and any special requirements relating to access, amenity, etc. 2 The options available for managing shoreline frontages vary widely around the Harbour and depend on the Managed realignment local circumstances. These General Guidelines set Improve shoreline performance by moving defences to out a three staged approach to identify an appropriate a more suitable location further inland, allowing flooding option. The three stages relate to the following: to occur between the new and old lines of defence. If carefully managed, this can result in the creation of • Strategic Policies. saltmarshes. • Typical Plan Layouts. • Typical Cross Sections and Construction Details. Managed realignment schemes allow controlled change in the shape of the Harbour’s shoreline. The Having identified an appropriate option, the following existing line of defence is removed or breached, and steps are normally required: a new structure constructed landwards, allowing the land in-between to become inundated, creating new • Develop outline design with dimensional drawings, intertidal habitat. technical specifications and method statements. • Obtain all the necessary consents and licences. In some cases where the existing defences are fully • Develop detailed design for construction stage. removed, this leads to a new location of the shoreline. • Undertake construction. In other cases, known as habitat creation schemes, the • Compile detailed record (Health and Safety file) of existing shoreline defence is maintained, but breached construction works. in controlled locations. The existing line of the shoreline is maintained, and any existing access managed using bridges.

Examples of habitat creation schemes in the Harbour are at Cobnor Point and Thornham Point.

15 3

Hold the line / hold the line (no public funding available) • Maintain: defences are maintained at their current levels, but as sea levels rise, flood risk increases over time. • Sustain: existing defences are raised and strengthened as sea levels rise keeping the level of flood risk the same as it is now. • Improved: new defences are installed or existing defences are improved.

16 Order of preference

1 2 3 Strategic Policies No active Hold the line (see page 16) intervention and / adaptive Managed Hold the line management of realignment (no public an existing or funding natural defence available)

1. Managed 1. Hold the line Order of preference realignment using secondary with no reuse of defence existing defence 2. Hold the line Typical Plan along existing Layouts 2. Managed line (see page 18) realignment with 3. Hold the line partial reuse of using imported existing defence material 4. Hold the line using groynes

• Surface layer structure Typical Cross • Embankment Sections and formation Construction • Piled structure Details • Gravity structure (see page 26) • Bed formation using groynes

In all instances, Chichester Harbour Conservancy would seek sound justification that the choice of shoreline defence is the most appropriate for the location.

17 4.0 Typical Plan Layouts 4.1 Shoreline Defence Options

The Typical Plan Layouts set out the main options for locating the shoreline defences relative to the existing line of defence. These comprise the following:

1. Hold the line along the existing line, where a new 4. Hold the line using a secondary set back defence, defence in its entirety is located along the line of the where the existing defence is still maintained in existing defence. some form in order to provide partial shelter to the new set back defence. 2. Hold the line using imported material, where new material is located seawards of the existing 5. Managed realignment with partial use of existing defence. The existing defence is still maintained by defences, where all of the new defence is located refurbishment or new construction but is partially landward of the existing defence and the existing sheltered by the new seaward works. defence is partially removed with the remaining sections still being maintained. 3. Hold the line using groynes, where new groynes are located seaward of the existing defence. The 6. Managed realignment with no re-use of existing existing defence is still maintained by refurbishment defences, where all of the new defence is located or new construction but is partially sheltered by landward of the existing defence and the existing natural or imported material trapped by the groynes. defence is removed, or allowed to deteriorate in a controlled manner.

All the defence options also have cost implications, which is likely to be taken into consideration as well. However, while cost may be a factor for the landowner, this will not affect whether any given proposed scheme is given permission or otherwise.

Managed realignment under construction at Cobnor, 2013.

19 4.2 Hold the Line along the Existing Line

Land

New primary defence along line of existing defence

Foreshore

This is where a new defence is constructed along the line of the existing defence. The height and/or depth of the defence may be increased and the type of construction may be changed. This can apply to both erosion and flood protection.

Armour-loc defences at Nore Barn Woods.

Advantages Disadvantages

• Existing ‘platform’ already in place for • The sloping surface results in a larger footprint developing new works. in the SAC.

• Particularly suitable for refurbishing existing • May exacerbate coastal squeeze. defences.

20 4.3 Hold the Line using Imported Material

Existing primary defence maintained Foreshore levels raised using imported material

Compatible imported material placed on the foreshore in front of the existing defence in order to raise foreshore levels. Existing defence still maintained although its level of exposure is reduced. This approach only applies to erosion protection.

Shingle replenishment is in keeping with the natural character of the Harbour.

Advantages Disadvantages

• Material may be available from maintenance • Risk of material losses due to natural processes. dredging within the Harbour. • Changes in character and level of foreshore • Represents a ‘soft’ engineering solution in may adversely affect existing natural processes keeping with the character of the Harbour. and habitats. • Strict consent framework for works of this nature.

21 4.4 Hold the Line using Groynes

Existing primary defence maintained Foreshore levels raised using imported material or by natural processes

Groynes constructed on the foreshore in front of the existing defence in order to contain imported material or trap existing mobile sediments. Existing defence still maintained although its level of exposure is reduced. This approach only applies to erosion protection.

Groynes trap material between them, like these at East Head.

Advantages Disadvantages

• Material may be available from maintenance • When relying on the natural build-up of dredging within the Harbour. existing mobile sediments there remains some • The addition of groynes reduces risk of material uncertainty on the levels achieved. being lost due to natural processes. • The groynes partially detract from the otherwise ‘soft’ engineering approach of raising foreshore levels. • Groynes may have an adverse effect on adjacent lengths of shoreline.

22 4.5 Hold the Line using Secondary Defence

New secondary set back defence Existing primary defence maintained

Additional modest-sized structure constructed behind the existing defence in order to raise the overall height of the flood protection. Existing defence still maintained as primary line of defence. This mainly applies toflood protection.

Chidham bund is a raised secondary defence set away from the existing shoreline, which can be seen in the top-left side of the photograph.

Advantages Disadvantages

• Avoids potential need to strengthen existing • Area of land between primary and secondary defence in order to accommodate increased lines of defence subject to intermittent flooding. height. • Secondary defence may hinder access to the • Allows for an alternative form of construction to shoreline. that used in the existing defence.

23 4.6 Managed Realignment with Partial use of Existing Defence

New primary set back defence Existing defence breached or lowered and then maintained

The existing defence is breached in pre-determined places or lowered along whole length, and a new moderate sized structure is constructed behind the existing line of defence. Remaining existing defence still maintained. This can apply to both erosion and flood protection.

At Cobnor the existing defences were breached and access bridges were built across the breach.

Advantages Disadvantages

• Alleviates coastal squeeze within the Harbour • Loss of agricultural land. without the need for a full sized replacement • May hinder access to main body of water due defence and a complete removal of existing to double line of defence. defence. • Potential loss of valuable habitat • Allows for the potential creation of a saltmarsh (e.g. coastal grazing marsh). forming between the two lines of defence.

24 4.7 Managed Realignment with No Re-use of Existing Defence

New primary set back defence Existing defence removed or allowed to deteriorate

Existing line of defence removed or allowed to deteriorate in a safe and controlled manner and new full sized structure constructed behind the existing line of defence. This can apply to both erosion and flood protection.

The west Chidham primary defence. It is anticipated that these unsightly and failing defences, not in keeping with the Area of Outstanding Natural Beauty designation, will be removed.

Advantages Disadvantages

• Reduces coastal squeeze within the Harbour • Loss of agricultural land. whilst maintaining a single line of defence.

25 5.0 Typical Cross Sections and Construction Details 5.1 Types of Defence

This section sets out the main options for discrete Each one can be used as a standalone defence or in types of defence in terms of their cross section, combination with others. They can be used in various and then for each type provides details on potential sizes to suit the local situation or their combination with variations that can apply in determining its exact other types of defence. The overall difference between shape, the separate elements that make up the whole the various options mainly relates to the particular way structure, and the materials used. in which they function and their general impact on the surrounding environment. The discrete types of defence are as follows: For the potential variations in the exact shape, 1 Surface Layer Structure. the separate elements and the materials used, 2 Bed Formation. commentaries are provided on the main issues that 3 Embankment Formation. need to be addressed when considering the options for 4 Gravity Structure. detailed design. 5 Piled Structure.

Riprap construction at Cobnor.

27 5.2 Surface Layer Structure

Foreshore Coastal slope Land

Crest

Slope gradient

Toe

Construction of a protective layer to a coastal slope that is otherwise naturally stable. The protective layer is sufficiently robust to resist tidal and wave action. It can apply to botherosion and flood protection and can be combined with bed formation and embankment formation.

Advantages Disadvantages

• Overall configuration follows natural coastal • May hinder access onto foreshore or into water. slope. • Lends itself to future increases in height and/or depth and therefore to adaptive management. • Use of porous materials may encourage natural build-up of foreshore levels.

Surface layer structure shoreline defence at Prinsted beach.

28 Potential Shape Variations Commentaries

• Slope gradient. • The gradient should not be steeper than the naturally stable gradient of • Toe detail. the underlying coastal slope. • Crest detail. • Shallower gradients are more stable. • Intermediate berm detail. • Toe detail should be sufficiently deep to avoid undermining. • Crest detail should minimise the risk of damage due to overtopping or surface water run-off. • Intermediate berms may be included to enhance the environmental performance of the structure.

Potential Separate Elements

• Anchorage system. • The number of separate elements will largely depend on the degree of • Foundation layer. exposure to wave action within the Harbour. For sheltered areas a single • Under layer. layer may be sufficient. For exposed areas a multi-layered approach may • Top layer. be required in order to provide the necessary protection and stability.

Potential Materials

• Natural vegetation. • The most appropriate material will largely depend on the degree of • Coir matting. exposure to wave action within the Harbour. Aesthetic considerations • Brushwood matting. will also need to be taken into consideration. • Geo-synthetic matting. • For sheltered areas more natural solutions such as vegetation or • Natural stone. brushwood matting may be sufficient. • Concrete blocks. • For exposed areas hard engineering solutions such as concrete blockwork or natural stone may be necessary. • For an intermediate situation a combination of natural and hard solutions may be appropriate. These may include natural vegetation reinforced with geo-synthetic matting or natural stone with intermixed vegetation.

29 5.2 Surface Layer Structure (continued)

Natural vegetation Coir Matting Brushwood Matting

Geo-synthetic Matting Natural Stone Concrete Blocks

Concrete Blocks

30 5.3 Bed Formation

Foreshore Coastal slope Land

Slope gradient

The raising of foreshore levels using a compatible material to reduce the exposure of the coastal slope to wave action. This only applies to erosion protection but can be combined with a surface layer structure, an embankment formation, a gravity structure or a piled structure.

Advantages Disadvantages

• Material may be available from maintenance • Risk of material losses due to natural dredging within the Harbour. processes. • Represents a ‘soft’ engineering solution in • Changes in character and levels of the keeping with the character of the Harbour. foreshore may adversely affect existing natural processes and habitats. • Will require a higher level of post-construction monitoring and maintenance compared with rigid defences. • May interfere with navigation. • May interfere with access to the shoreline.

31 5.3 Bed Formation (continued)

Potential Shape Variations Commentaries

• Slope gradient. • Slope gradient should be reasonably close to the existing foreshore • Berm at top of slope. gradients. An over steep gradient is likely to result in a premature loss of material. • A berm at the top of the slope can significantly increase the effectiveness of the bed formation.

Potential Separate Elements

• None. • As a general rule with this type of work the bed formation would be in a single layer of one type of material.

Potential Materials

• Mud. • These would depend on the nature and characteristics of the existing • Sand. foreshore and would need to be a close match. • Shingle.

32 5.4 Embankment Formation

Foreshore Coastal slope Land

Slope gradient Low Lying Land

The raising of ground levels using bulk materials to form a barrier against flooding. (A similar concept can be used to form groynes on the foreshore, constructed in natural stone). An embankment mainly applies to flood protection. It can be a secondary defence behind an existing defence and it can be combined with a gravity structure or a piled structure.

Advantages Disadvantages

• Overall configuration can be made to blend in • Large footprint compared with gravity structure with natural landscape. and piled structure. • Lends itself to future increase in height and • Requires significant quantities of imported therefore to adaptive management. material. • Can represent an environmental enhancement • Requires stabilisation and long-term if natural vegetation is used for surface layer. maintenance of outer face.

The raised footpath at east Chidham (left) and the bank at Northney Farm (right) are examples of an embankment formation.

33 5.4 Embankment Formation (continued)

Potential Shape Variations Commentaries

• Slope gradients. • The slope gradients should not be steeper than the naturally stable gradient for the type of material used.

Potential Separate Elements

• Foundation layer. • A foundation layer may be required if the underlying ground has a low • Core. bearing capacity. • Outer layer. • A separate core may be appropriate in order to achieve overall • Surface layer. construction efficiencies. Compared with the outer layer the core may be in a lighter, less permeable or lower quality material. • A separate surface layer may be necessary for aesthetic and/or environmental reasons.

Potential Materials

• Geo-synthetic layer. • For ‘earth fill’ a range of materials should be suitable provided they are • Earth fill. workable, stable and uncontaminated. • Topsoil. • Also the core and/or outer layer should be sufficiently impermeable to • Natural vegetation. resist seepage from high water levels. • Natural stone (for groynes).

34 5.5 Gravity Structure

Foreshore Land

Low Lying Land

Toe Base

A heavy-duty rigid construction that uses hard materials, relies on its weight for its stability, and forms a barrier against coastal erosion and flooding. Can be a secondary defence behind an existing defence or combined with a piled structure.

Advantages Disadvantages

• Small footprint compared with embankment • May appear out-of-keeping with the natural formation. landscape. • Provides a robust platform for the construction • May encourage lowering of foreshore levels of amenity and other works. due to wave reflection off vertical face.

The Bosham Trippett Wall is an example of a gravity structure.

35 5.5 Gravity Structure (continued)

Potential Shape Variations Commentaries

• Toe detail. • Toe and base details should be sufficiently deep and wide to provide • Base detail. stability and avoid undermining. • Profile of front face. • Profile of front face should suit any aesthetic, amenity or environmental requirements.

Potential Separate Elements

• Foundation layer. • The need for a foundation layer and/or drainage layer will depend on the • Core. local conditions. • Front face cladding. • The use of a separate cladding layer may be appropriate in order to • Rear face drainage layer. achieve overall construction efficiencies. Compared with the core the cladding may be in a higher quality and/or more aesthetic material.

Potential Materials

• Concrete. • A range of conventional construction materials should be suitable • Concrete bagwork. provided they are sufficiently robust and durable. • Brick. • Stone blockwork. • Timber.

36 Concrete Concrete Bagwork Brick

Stone Blockwork Timber

37 5.6 Piled Structure

Foreshore Land

Capping detail

Low Lying Land

Construction works that rely on their embedment into the underlying ground for their stability, and form a barrier against coastal erosion and flooding. (A similar concept can be used to form groynes on the foreshore). A piled structure can be a secondary defence behind an existing structure and can be combined with a surface layer structure or a gravity structure.

Advantages Disadvantages

• Very small footprint compared with • Heavier-duty solutions may be out-of-keeping embankment formation. with natural landscape. • Can represent an environmental solution if • Heavier-duty solutions may encourage lowering lighter-duty more natural materials are used. of the foreshore due to wave reflection off vertical face.

The timber log larch posts at Dell Quay form a piled structure.

38 Potential Shape Variations Commentaries

• Capping detail. • Capping detail should suit structural, amenity and/or aesthetic requirements.

Potential Separate Elements

• Piles. • Piles may be contiguous or spaced apart with in-fill panels. • Capping beam. • For structural purposes a horizontal waling may be necessary. • Waling. • For structural, amenity and/or aesthetic purposes a horizontal capping • In-fill panels. beam may be required. • Cladding.

Potential Materials

• Timber logs. • The most appropriate materials will largely depend on the height of • Timber posts. the structure and its degree of exposure to wave action. Aesthetic considerations will also need to be taken into account.

Timber Posts

39 6.0 Further Information

6.1 Glossary

For further information on the various designations in Chichester Harbour, please refer to page 6.

Term Description Adaptive Management For shoreline defences, a process by which existing structures are modified in stages over an extended period of time to suit changes in the prevailing conditions. Bearing Capacity The capacity of underlying soils to support the loads applied to them without losing their structural integrity. Capping Beam A structural member along the top edge of a piled wall designed to strengthen the structure and/or improve its appearance. Cladding For shoreline defences, a surface layer that overlays the parent structure with the purpose of improving appearance and/or durability. Coastal Squeeze The progressive reduction and loss of foreshore coastal habitat area and natural features which can arise if the natural landward migration of a habitat under sea level rise is prevented by man-made defences and structures. Dredging Artificial removal of silts, sands, shingle and/or other underwater sea-bottom materials. Environmental Enhancement Specific measures or features for improving the environmental quality of a shoreline defence. Epoch A distinctive point in time. Erosion In the Harbour context, the loss of land as a result of the retreat of the shoreline due to tidal and wave forces. Flooding In the Harbour context, the inundation of land adjacent to the shoreline due to overtopping of the defences or natural coastal slope.

40 Term Description Foreshore The zone between the low water and the high water marks. Historic Environment Record This relates to registered buildings, ‘find spots’ and monuments. There are 755 (HER) HER sites in Chichester Harbour. Hold the Line Maintain or upgrade the standard of protection provided by the existing defences. This covers situations where work or operations are carried out in front of the existing defences (such as beach recharge or groynes) to improve or maintain the standard of protection provided by the existing line of defence. This policy also involves operations to the back of existing defences (such as building secondary defences) where they form an essential part of maintaining the current shoreline defence system. Managed Realignment Managed Realignment (Retreat) involves the construction of a new defence landward of the existing defence and either removing the existing defence or allowing it to deteriorate in a controlled manner. Pile A long slender structural component that is driven into the ground. Porous A material that allows the passage of water through it. Sea Level Rise Current national guidelines predict a typical sea level rise of one metre over the next 100 years, roughly split between 30 centimetres over the next 50 years, and 70 centimetres thereafter. Wave Reflection Process by which incident waves are reflected off shoreline defences causing additional turbulence in front of the defence which can lead to local scour and/ or lowering of the foreshore.

41 6.2 Useful Websites

There is a wealth of further information available Chichester Harbour straddles the boundary between for anyone interested in shoreline defences. All the Hampshire and West Sussex. Havant Borough documents below are available online. Since legislation Council and Chichester District Council and have is an evolving field, we would advise that you contact both published their respective Local Plans, which the organisations below at the earliest opportunity to contain their overarching planning policies. These seek their respective guidance. organisations are also the respective Coast Protection Authorities. Depending on the scope of the project shoreline defences may also affect Hampshire County Council and West Sussex County Council, particularly if they are strategically important.

www.havant.gov.uk www.chichester.gov.uk www.hampshire.gov.uk www.westsussex.gov.uk

Defra and two of its agencies, Natural England and the Environment Agency, all have a strong interest in shoreline defences.

Natural England has published guidance for landowners and occupiers of SSSI land and is in the process of updating their conservation advice for Chichester Harbour Conservancy publishes Marine Protected Areas, which includes SAC, SPA and the AONB Management Plan and is a non-statutory Ramsar sites. The advice highlights the potential impact consultee in the planning process. It is advisable to speak of specific operations, including shorelines defences, to the Conservancy staff in the first instance. on these habitats and the species they support. www.conservancy.co.uk Natural England also offers a Pre-Planning advice service:

The North Solent Shoreline Management Plan https://www.gov.uk/guidance/developers-get- extends between Selsey Bill, in the east, and Hurst environmental-advice-on-your-planning-proposals Spit, in the west, and includes Portsmouth, Langstone and Chichester Harbours. This Plan divides Chichester The Environment Agency’s ‘Estuary Edges’ document Harbour up into distinct sections and advises on policy details how landowners can make a positive impact to options for three epochs: present day to 2025; 2025 their environment. to 2055; and 2055 to 2115. For any given landowner considering shoreline defences, it is well-worth www.gov.uk checking the exact policy in this Plan to ensure that the approach is consistent with this wider strategy. A good source of information is also the Coastal Defence and Biodiversity website, which brings www.northsolentsmp.co.uk different information together into once place. The website was set-up by the University of Glasgow and the University of Oxford.

www.biogeomorph.org

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