Sand Dune Management Techniques & Preliminary Decision Support Tool

Appendix A Sand Dune Management Techniques & Preliminary Decision Support Tool v2.0

(NB: See accompanying CD to access the tool, which is only provided in digital format)

REPORT

Sand Dune Management Techniques & Preliminary Decision Support Tool v2.0

Prepared for Cornwall Council

November 2015

Halcrow Group Limited, a CH2M HILL Company Ash House, Falcon Road, Sowton, Exeter, Devon, EX2 7LB UK +44 1392 444 252 +44 1392 444 301

Contents

Section Page 1 Introduction ...... 1 1.1 Background and context ...... 1 1.2 About this report ...... 2 2 Management Techniques ...... 3 3 Dune Management Preliminary Decision Assistance Tool User Guide ...... 22 3.1 Introduction ...... 22 3.2 Using the tool ...... 22 References ...... 28

Appendices Appendix A Dune Management Preliminary Decision Assistance Tool

III

1 Introduction 1.1 Background and context Cornish dune sites are subject to high visitor numbers and the development of tourist amenities both within and behind the dune system. Sites are also subject to significant natural pressures, and storm wave conditions often result from a long fetch across the Atlantic and the relatively steep near‐shore bathymetry at many sites which produces high levels of wave energy at the coast. Climate change and sea level rise provide further pressures on Cornish dunes whose transgression landwards in response to sea level rise is limited by the surrounding tourism development and rising land levels. As a result of these pressures, dune management is required to maintain the flood and coastal defence properties of the dunes, while also enabling the important tourism economy to thrive. The various uses of the dunes often conflict, with stable fixed dunes being preferred for flood management schemes, dynamic dunes preferred with slacks and blow outs for habitat value, and higher visitor numbers required for the tourist economy. Conflicts between recreation and conservation are typical of the Cornish dune sites. Dune management can provide a number of benefits to the dunes including (CIRIA, 2010):  Increased aesthetic value of the beach and dunes;  A reduction in the need for fixed flood defence structures. This, however, can also increase the requirement for:  Regular monitoring and interference with natural processes;  Labour and time intensive management schemes;  Increased public awareness leading to concern over storm impacts;  Limited public access to part of or the entire site. The first aspect for consideration in dune management is whether the site actually requires management. Preliminary surveys and site monitoring should be carried out to assess the condition of the site. The BTCV (2005) suggest a list of questions to clarify management requirements. They suggest it is important to distinguish between natural and human or human related impacts and, where possible, only the human influenced problems should be managed. Techniques that interfere with the natural dynamics of the dunes should only be employed as a last resort. Over‐management of dunes should be avoided where possible (Carter, 1988). A diverse dune system with features such as blow outs and slacks is thought to be more able to react to changing conditions than a system in which all blown sand is trapped and covered with uniform planted vegetation. Management should therefore work with the natural system where possible, rather than preventing all dynamic natural processes. Once the dune site has been evaluated and it is clear what the problems are and what the underlying cause for these is, the relevant dune management techniques can be identified. There are a large variety of techniques that are applicable to the wide variety of dune sites and problems across the world.

1.2 About this report To aid coastal managers in identifying appropriate management approaches, as part of the Cornwall Sand Dunes & Beach Management Strategy completed in 2009, a review of available literature was carried out to produce a summary of national and international techniques for sand dune management (Halcrow, 2009). That work has been reviewed in 2015 as part of the Cornwall Beach & Dune Management Plans project and additional techniques have been identified. Section 2 of this report provides a summary of the dune management techniques practised worldwide to manage dunes for flood and coastal defence purposes first identified in 2009, and updated in 2015. In order to create a sustainable and long term management scheme a combination of these techniques may be required. A nourishment scheme for example may require planting, binding and fencing to stabilise the sand surface following the nourishment, and groynes may be required to retain the new beach material. This information is presented in Section 2 as a summary table of management techniques and can be used by sand dune managers as a reference for the planning of dune management schemes. The information, along with further details, is also included in a ‘Preliminary Decision Assistance Tool’ which can be used by site managers as a first indication of what techniques would be appropriate for the problems encountered at their site. It is presented as a Microsoft Excel document in Appendix A of this report. Section 3 of this report provides an overview and user guide as to the contents of the tool.

2 Management Techniques

A review of available literature was carried out to produce a summary of national and international techniques for sand dune management in 2009 (Halcrow, 2009) and this has been reviewed as part of this current project. Table 2‐1 provides a description of the management technique along with: a reference given for further information on that technique (where applicable); an indication of when the technique is appropriate; and the associated benefits and problems associated with the technique. Where possible, an example of a sand dune site in Cornwall is provided where the technique is in use. The methods listed can be used in combination to produce the most appropriate management approach for a specific sand dune site. Adaptive management involves the application of dune management alongside detailed monitoring of the site. Through assessment of the results of ongoing monitoring, management techniques can be modified and refined. Through ongoing monitoring, management and adaptation, a successful and sustainable management approach can be developed. The categories of management identified in Table 2‐1, in alphabetical order, are:  Access management;  Adaptation of backshore management/uses;  Cease existing management;  Ecological modification;  Funding;  Hard protection methods;  Manual maintenance;  Monitoring;  Morphological modification;  Public awareness;  Sediment modification; and  Stabilisation.

Table 2‐1 Summary of Sand Dune Management Techniques

Technique When Appropriate Benefits Problems Example Site

ACCESS MANAGEMENT Zoning  Tourist sites where erosion is  Natural processes can  Amenities such as picnic Cornwall Planning of the site to reduce or spread the taking place due to visitor continue. areas may attract further Gwithian to Mexico Towans. impact of visitors. Tactics are employed in site numbers.  Eroded areas are able visitors.  Perranporth (Penhale Sands). planning which encourage visitors to less to recover.  Potential vandalism of sensitive zones and discourage them from signs and fencing.  These sites are managed by sensitive areas. This includes consideration of rangers to limit damage to aspects such as: the sensitive habitats.

 Location of amenities. Other  Location and size of car parks.  Sefton Coast Dunes England.  Location of campsites.  Kennemerduinen National  Fencing, boardwalks and planting to Park, west central Holland. discourage visitors from straying into sensitive areas (see below)  Ability to rotate visitor attractions such as picnic areas.  Limit/ prevent vehicle access.  Fees such as car park tickets set at a rate to limit visitor numbers.

(Carter, 1988) Boardwalks  Sites with high visitor numbers  Limits trampling and  Expensive to construct Cornwall Generally constructed on fore dunes to where pedestrian traffic is erosion along main and require  Hayle Towans (Part of Mexico prevent lowering of dune and development of concentrated along access routes. maintenance. to Gwithian Towans). blowouts when pedestrian traffic is routes causing erosion and dune  Encourages visitors to  May impact upon natural  Sennen Cove. concentrated along access paths. lowering. keep to designated dune processes. paths. Other (BTCV, 2005)  Morfa Dyffryn, North Wales.

Technique When Appropriate Benefits Problems Example Site

 If not designed correctly  La Dune de Bouctouche, can increase wind along the Northumberland erosion. Strait near Bouctouche,  Vandalism may be a Canada. problem.  Sefton Coast Dunes, England.

Control Fencing  Sites with high visitor numbers,  Limits trampling and  Expensive to construct Cornwall Fencing designed to prevent visitor access to where access to sensitive areas erosion of protected and requires ongoing  Fistral Beach. sensitive areas and contain visitor traffic is restricted to prevent areas. maintenance.  Sennen Cove. designated access routes. problems such as trampling.  Encourages visitors to  Vulnerable to storm  Praa Sands. keep to designated wave damage when Low wind resistance fencing, such as wider paths. located along front of Other spaced posts with galvanised steel wire, is  Enhances natural dunes.  Magilligan Sand Dunes, North required to prevent sand build up. dune recovery.  Vandalism may be a West Ireland.  Relatively low cost. problem.  Texel, The Netherlands. (SNH, 2000; BTCV, 2005)  Materials often taken to build bonfires.  Damaged fences can be visually unattractive.  Maximum life of 5 years.

Use of Information Boards  To use alongside defined routes  Reinforces messages.  Requires ongoing Cornwall through dunes, to provide maintenance.  Summerleaze explanation and information  Widemouth Bay why to use the official route  Praa Sands and not trample the dunes.  Porthtowan  Par Sands.

Technique When Appropriate Benefits Problems Example Site

ADAPT BACKSHORE MANAGEMENT/USES Adapt Backshore Management/Uses  Low value locations where  Natural processes can  Loss or movement of Cornwall Allow natural processes to continue and adapt backshore assets are moveable continue. backshore assets.  None identified. backshore management accordingly. May or have reached the end of their  Potential benefits to  Control of backshore involve moving, replacing or demolishing residual life. adjacent frontages. developments. backshore assets which are at risk, and  No ongoing  Possible conflict due to Other controlling future backshore developments. maintenance costs. different opinions of  None identified.  Highly sustainable asset value. (SNH, 2000; CH2M, 2015) over medium to long term. CEASE EXISTING MANAGEMENT Remove Defence Structures  Sites with a negative sediment  Greater dune mobility  Not suitable for low lying  No existing sites in Cornwall. Eroding dunes, or low dunes which do not budget or high energy increases habitat densely populated areas. provide appropriate flood protection are often conditions, and hard structures diversity.  Not suitable where fronted by hard defences. On high energy fronting dunes.  Economic benefit as backing development beaches with a negative sediment budget reduces maintenance does not allow dunes to these structures are of limited benefit. As hard costs. migrate landwards. defences have a finite life and require  Environmental benefit  Sand may blow into maintenance it can be beneficial economically as increases habitat downdrift areas and and environmentally to remove the structures. diversity. become a nuisance. A full cost benefit analysis may be required  Can reinstate natural which includes environmental values. beach dune interaction. (Pye, 2007)

Technique When Appropriate Benefits Problems Example Site

Cease Mechanical Litter Clearing  Where the dune front is eroding  Enables natural  Non mechanical beach Cornwall Beach cleaning using mechanical methods and mechanical beach cleaning accretion and embryo cleaning may be more  Bude. removes not only litter but also natural is carried out at present. dune development. time consuming and materials such as strandline seaweed and hence more costly. Other sand. Removing this material removes the  Seaweed should be left  Guernsey. natural obstacles which would catch and trap on the beach which may sand to encourage sand deposition and the not be ideal on amenity development of embryo dunes. Such cleaning beaches. methods can also destroy embryo dunes at an early stage in their evolution. (see MANUAL MAINTENANCE).

A sand dune system with the physical conditions for accretion can actually be stable or eroding as a result of mechanical beach cleaning preventing accretion along the dune front. ECOLOGICAL MODIFICATION Maintain existing condition  UK Biodiversity Action Plan  Maintains existing  Habitat management This will vary from one site to the next, but Priority Habitats (coastal sand ecological health of requires ongoing could include items such as: dunes, maritime cliff and slope) the dunes which is maintenance  Ongoing regular maintenance such as are generally in unfavourable important in working commitment, funding cutting back. condition. with natural for which may not be  Maintain existing water levels in an processes to provide available. area, such as intertidal habitat by coastal flood and maintaining any defences that erosion risk control water levels. management with  Allow coastal processes to continue the aid of sand on maritime cliff/slope (no dunes. management intervention). Improve existing condition  UK Biodiversity Action Plan  Improves existing  Habitat management Priority Habitats (coastal sand ecological health of requires ongoing

Technique When Appropriate Benefits Problems Example Site

This will vary from one site to the next, but dunes, maritime cliff and slope) the dunes which is maintenance could include items such as: are generally in unfavourable important in working commitment, funding  Removal of non‐native invasive condition. with natural for which may not be species within the dune vegetation. processes to provide available.  Planting with additional vegetation, coastal flood and such as marram grass. erosion risk management with the aid of sand dunes. FUNDING Seek funding from Environment Agency  New / repairs to existing or  Will provide required  Funding may not be new defences required. asset / management justified on economic  Management techniques technique thereby grounds. require funding. improving dune quality, ecology and subsequently their defence function. Seek funding from Local Authority  New / repairs to existing or  Will provide required  Funding may not be new defences required. asset / management justified on economic  Management techniques technique thereby grounds. require funding. improving dune quality, ecology and subsequently their defence function. Seek funding from sole private source  New / repairs to existing or  Will provide required  Funding may not be new defences required. asset / management justified on economic  Management techniques technique thereby grounds. require funding. improving dune quality, ecology and subsequently their defence function.

Technique When Appropriate Benefits Problems Example Site

Seek match funding (government+ third‐  New / repairs to existing or  Will provide required  Proportion of funding party) by establishing a funding partnership. new defences required. asset / management from Government may  Management techniques technique thereby not be justified on require funding. improving dune economic grounds so quality, ecology and may need to rely solely subsequently their on third‐party sources. defence function. HARD PROTECTION METHODS Sand Bag Structures  Sites with low to moderate  Low to moderate cost.  Life < 5 years. Other Sand bags of various sizes and length are used wave energy where lower cost,  Low skills required.  Sand bags often  Atlantic City (near Rhode to construct temporary reefs, breakwaters, temporary defences are  Local materials are vandalised. Island Avenue), USA – groynes, headlands or revetments. This required. used and returned to  Rapid deterioration Geotubes filled with sand. provides a short term fixed defence. the beach when the resulting from wave defences are no action. (SNH, 2000) longer needed.  Beach scour may accelerate as bags are non‐permeable and wave energy is not absorbed. Gabion Revetments  Sandy sites with periodic  Moderate cost.  Ongoing maintenance Cornwall Provides short term protection from erosion moderate to severe erosion with  Useful when rock required.  Fistral Beach. by absorbing wave energy along the dune backshore assets at risk. armour is  Limited lifespan of 5‐10  Perranporth. face.  Particularly useful as estuary inappropriate or too years. bank protection. expensive.  Degradation leads to ugly Other Wire mesh baskets are filled with cobbles or  Provides alternative to rock  Numerous forms and hazardous wire  Minch Area, Scotland. crushed rock. This can be done in situ using armour where large rocks are available. baskets along the beach  Hengistbury Head, England. local material to reduce costs. Baskets can be not available at a reasonable  May be buried by and releases non  Old Hunstanton, North placed as sloping mattresses or near vertical cost or where long term sand and/or indigenous cobbles to the Norfolk. cubic baskets. Sloping mattresses tend to be protection is not appropriate. vegetation. system. most appropriate for beach sites.  The permeable face  Wire is degraded by absorbs wave energy seawater, trampling and (SNH, 2000) and encourages upper gravel beach impacts. beach stability.  Often vandalised.

Technique When Appropriate Benefits Problems Example Site

Artificial Headlands  Rapidly eroding dune sites  Low maintenance with  Visually intrusive. Cornwall Rock structures constructed along the dune where significant backshore moderate cost.  Erosion only controlled at  Bude. toe to protect appropriate points. Natural assets are sited at intervals  Local protection to targeted locations. processes are able to continue between the along the beach. targeted areas with  Structures can interfere Other headlands. Headlands can be formed from minimum disturbance with longshore transport  Barton on Sea, England. gabions or sandbags but life expectancy would to overall natural (in particular on be 5‐10 years. system. sand/gravel beaches).  Once in place  Structures may require Can be used in combination with other low modification or periodic extension or cost techniques. removal is possible. relocation landward to  Rock headlands have avoid outflanking. (SNH, 2000) long structure life. Artificial Reefs  Exposed dune sites with high  Rock structures have  Moderate to high cost. Cornwall Shore parallel rock mound structures located ecological and landscape values. long structure life.  Shoreline maintenance  No existing sites in Cornwall. part way down the beach face. Reefs dissipate  Natural processes only may be required. part of the incident wave energy before waves partly disrupted.  May cause a navigation Other reach the dune face. This protects from  Rocks create new hazard.  Antigua Maiden Island. erosion and encourages deposition. May be a intertidal habitat.  Visually intrusive at low long single structure or a series of reefs tide. extending alongshore. These structures are  Impact upon amenity different from Shore Nearshore Breakwaters value of beach. (see below) because they are submerged for at least part of the tidal cycle.

(SNH, 2000) Nearshore Breakwaters  High value dune sites.  Good protection  Potentially damaging to Cornwall Shore parallel segmented structures which can  Must have low longshore within enclosed bays. open coast sites.  No existing sites in Cornwall. be located along the upper beach in the transport rates and weak  Causes lee side  Erosion behind gaps intertidal zone, or often at the high water nearshore tidal currents. accretion. where wave energy Other mark. Often constructed of rock, but concrete  Dunes are not directly reaches the beach and  Dornoch Firth, Scotland. armour units can also be used. disturbed. dune face.  Visually intrusive.

Technique When Appropriate Benefits Problems Example Site

The breakwater reduces the energy of the  Increases dry area of  Changes upper beach waves reaching the beach, while not isolating upper beach. morphology. the dunes from the beach system.  New foredunes may  Fine sediment, seaweed stabilise. or debris can accumulate Different from artificial reefs as they are on upper beach. located further up the beach.  Can cause strong currents which are a (SNH, 2000) hazard to beach users.  May cause downdrift erosion. Groynes  High value frontages with  Moderate cost (but  Disrupt longshore drift. Cornwall Cross shore structures which reduce longshore significant longshore processes must add cost of  Disrupt public access  No existing sites in Cornwall. transport on open coastlines or deflect (due to waves or tides) where nourishment/ along beach. nearshore currents within an estuary. On open nourishment or recycling recycling).  Downdrift erosion may Other coast beaches groynes limit longshore drift by schemes are implemented.  Aids upper beach occur if beach is not  Hunstanton, Norfolk. trapping material and causing the beach stability. carefully managed.  Prestatyn, North Wales. orientation to change relative to the dominant  Reduces maintenance wave direction. Constructed as a series along for nourishment and open beaches to reduce longshore drift recycling schemes. following nourishment or recycling schemes. A  Rock groynes have single structure may be used in estuary long structure life. locations.

Rock groynes are favoured, gabions may be implemented for more temporary structures.

May be implemented in combination with revetments. Used to retain material in combination with beach nourishment.

(SNH, 2000)

Technique When Appropriate Benefits Problems Example Site

Rock Revetments  Sites with severe ongoing  Low maintenance.  High cost. Cornwall Rocks are used to armour the dune face, erosion affecting extensive  Long term protection  Large visual impact.  Praa Sands. dissipating storm waves and preventing backshore assets.  Can be extended/  Permanently changes further backshore recession (if well designed modified in line with dune system. Other and maintained). future changes.  Sand will not accrete  East Head, England.  Low risk option for over rocks if ongoing  Prestatyn, North Wales. Can range from detailed engineered structures significant backshore erosion continues. along lengths of coastline to roughly placed rip assets.  Impact upon recreational rap protecting patches of severe erosion. Absorbs wave energy use – access must be and aids upper beach provided. (SNH, 2000) stability. Timber Revetments  High value sights with modest  Generally acceptable  Limited life where Cornwall Implementation ranges from substantial, and periodic erosion. Best in low to the public. exposed to wave action  No existing sites in Cornwall. impermeable breastwork to temporary wave energy environments.  Moderate cost – less (5‐30 years where only permeable upper beach wave barriers. Can expensive than occasionally exposed to Other provide partial barrier to wave action when seawalls or rock wave action).  Dundrun Bay, Northern forming a permeable barrier along the upper revetments.  Visually intrusive. Ireland. beach or a wave protection wall when forming  Disrupts interchange of an impermeable vertical breastwork along the material between beach dune face. and dunes.  Sustainability of Widely implemented in the UK when seawall hardwood for more cost/ impact is not warranted. substantial structures is currently an issue. (SNH, 2000) Clay Embankments  Site where dunes are at risk of  Natural dune  Roll back of dunes may Cornwall Clay embankments may be used to protect overwashing or breaching processes can be limited by  No existing sites in Cornwall. against hinterland flooding. They can be causing backshore assets to be continue as dune embankment. located at the back of the dunes, acting as a at risk of flooding. Where beach interaction is  Can be visually intrusive. Other secondary flood defence to protect backshore environmental impacts of hard not impacted upon.  Skegness Dunes, (south of assets. defences located in front of the  Damage to dune Seathorne) England. dunes are undesirable. ecology is minimised.

Technique When Appropriate Benefits Problems Example Site

(CIRIA, 2010)

Impermeable Revetments and Sea Walls  Exposed sites with many high  Low maintenance.  High cost. Cornwall These form a fixed defence line across the value backshore assets.  Protection good in  Erosion will lead to  Marazion. front of the dune system. medium term. structural undermining Impermeable revetments consist of sloping  Enables development and failure. Other defence structures constructed of blockwork, up to the shoreline.  Severe disruption to  Prestatyn, North Wales. asphalt or mass concrete. Constructed along  Amenity facilities can beach dune interaction.  Llandanwg, North Wales. the dune face above the normal runup limit of develop along the waves. backshore.  Facilitates beach Sea walls are near vertical structures access. constructed of concrete, masonry or sheet pile. Commonly applied in the past seawalls are now considered to be unsuitable for dune sites as they are costly and damaging to the stability of the beach dune system.

(SNH, 2000) MANUAL MAINTEANCE Beach/sand cleaning  Litter is a problem due to high  Reduces/removes  Requires ongoing Undertake beach cleaning manually to avoid visitor numbers and existing direct impact on maintenance. adverse impacts caused by use of mechanical solutions to litter management ecology of the beach  Can be less methods. are not sufficient. and dune system, and effective/efficient as  BBQ’s are held within the dunes therefore natural often difficult to do as and litter is left behind. processes. regularly as mechanical  If utilise volunteer cleaning. beach cleans, invests community in ensuring litter is minimised in future.

Technique When Appropriate Benefits Problems Example Site

Ranger/warden  Access overlooked / public  Reduces/removes  Ranger/warden authority awareness signs ignored. direct impact on may be challenged.  BBQs held within dunes. ecology of the dune  Time constraints and system, and therefore effectiveness may be an natural dune issue. processes. Friends of the dunes group  Litter is a problem due to high  Minimal funding  Funding Cornwall visitor numbers. required from limited/unavailable and  Porthtowan  Where volunteer groups already Government/Local tasks rely on volunteers.  Par Sands exist or a willingness to start up Authority; most Uptake may be low.  Widemouth Bay a group. funding to be raised by dunes interest group. Provides support to ranger/warden for site (if one is in place). Raises awareness of issues.

MONITORING Monitoring Schemes  Appropriate at all sites both  Provides information  A continuous process Cornwall Monitoring of the beach dune system may be before and after on the state of the which is most useful in  Now implemented at all of implemented singly or in combination with implementation of management dunes and how they future rather than at the the Cornish Sites as part of any other management technique(s). schemes as well as at sites with are functioning. time of monitoring. As the SWRCMP. no management.  Provides information such the type of  Additional scheme specific Monitoring of an unmanaged system can be on the success of information likely to be monitoring may be required an important tool in monitoring how the dune management required in the future with some management system is adapting to changes in natural techniques must be carefully practices. forces, such as climate change. implemented, or prior assessed. to management  Quality of historic data Other This data can be used to determine whether indicates which must be assessed before  Regional Coastal Monitoring dune evolution will lead to an increase in flood management data is used. Programmes around the

Technique When Appropriate Benefits Problems Example Site

risk. The data can also be used to decide on techniques are coast of England appropriate management practices. appropriate. (www.coastalmonitoring.org).  Can be tailored to the In combination with other management site e.g. if storm techniques monitoring of the system will erosion is a known provide information on how the techniques problem post storm are functioning, enabling adjustments to surveys can be schemes if required. implemented.

Monitoring could include methods such as  Topographic surveys  Hydrographic surveys  Fixed photography  LiDAR (Light Detection and Ranging, effectively an airborne laser scanner)  Aerial photography  Laser scanning

(SNH, 2000; www.coastalmonitoring.org). Ecological Condition  Potential habitats in an area but  Awareness of ecology,  Funding require to Cornwall Mapping coverage and condition of uncertain as no previous thereby ensuring is undertake study may not  Fistral Beach designated/ecologically important sites. mapping/identification of sites conservation – be available.  Praa Sands undertaken. ecological health of  Harvey’s Towans the dunes is important  Porthtowan in working with natural processes to provide coastal flood and erosion risk management with the aid of sand dunes. Ecological Condition  Where there are potential UK  Confirm presence of  Requires survey and on‐ Cornwall Biodiversity Action Plan Priority non‐native invasive going monitoring  Fistral Beach

Technique When Appropriate Benefits Problems Example Site

Mapping coverage of non‐native invasive Habitats in the BDMP area, as and non‐invasive  Praa Sands species well as non‐native invasive species, and manage  Harvey’s Towans species that should be removed appropriately any that  Porthtowan if present. are present. MORPHOLOGICAL MODIFICATION Dune Fencing  Sites with available blown sand,  Low cost.  Ongoing maintenance Cornwall Fencing designed to increase dune height and where erosion is not severe.  Enhances natural required.  Marazion. width, improving flood and coastal defence  Fencing must be above normal dune recovery with  Can be destroyed by properties of dunes. limit of wave run‐up. minimal impact on storm wave action. Other natural system.  Materials often taken to  Texel, The Netherlands Semi permeable fences along the seaward  Can also be used to build bonfires.  Sefton Coast Dunes, England. face of the dunes encourage deposition of control public access  Maximum life of about 5  Brancaster Bay, North aeolian sand. As sand builds up around the and enhance other years depending on Norfolk. fencing it will become buried and new fencing schemes. material, wave action must be constructed. Double fencing or single  Can be designed to and vandalism. fencing may be used and the final dune form reduce wave attack at  Damaged fences can be is strongly related to the sequential toe of dune as well as visually unattractive. positioning of the fences. trap sand.  Sand trapping can Can be applied in combination with other reduce nuisance wind schemes to aid dune stabilisation and to blown sand in areas reduce environmental impacts. such as roads located downdrift of the (SNH, 2000; BTCV, 2005; Pye, 2007) dunes. Planting  Site with available blown sand,  Complements the  Dune fencing or Cornwall Strategic planting designed to increase dune where erosion is not severe. natural system by thatching normally  Hayle Towans (Part of Mexico height and width, improving flood and coastal  Planting must be above normal enhancing natural needed for planting to be to Gwithian Towans). defence properties of dunes. limit of wave run‐up. dune recovery. successful. Planting of foredunes with appropriate species  Can be used to  Potential for complete Other enhances deflation and encourages sand build enhance other loss of planting to a  Sefton Coast Dunes, England. up. A reservoir of sand held in the planted management options. storm event.  Morfa Dyfryn, North Wales.  Can be self sustaining.

Technique When Appropriate Benefits Problems Example Site

foredunes will provide a buffer to storm  Sand trapping can erosion. reduce nuisance wind Thatching, mulching and binding will aid blown sand in areas vegetation growth (see STABILISATION) such as roads located downdrift of the (SNH, 2000; BTCV, 2005; Pye, 2007) dunes. Bulldozing/Contouring  All locations, including those  Easy to achieve.  Effect is temporary on Cornwall Existing sand can be bulldozed to create new with limited blown sand for  Dunes can be formed steep narrow beaches  Hayle (Part of Mexico to sand mounds or to infill blow outs. natural recovery. into a stable with significant wave Gwithian Towans) Can also be used to reprofile dunes to a more aerodynamic shape. action. stable and aerodynamic shape.  Can be used to infill Other Contoured/ bulldozed dunes will require dune overwash breaches.  Formby, Sefton Coast, stabilisation methods to prevent deformation England. by wind action. (see STABILISATION).

(Pye, 2007) Beach Drainage  Sand beach sites with a low tidal  Low to moderate  High maintenance and Cornwall Perforated land drain pipes are buried below range, low to moderate wave initial costs. running costs.  Towan Beach, Newquay the upper beach and connected to a pump energy and a high amenity value  No visual impact.  Storm erosion is likely to (ceased in 1999) and discharge. The water table is lowered in  Results in wider, drier damage the drainage the swash zone, enhancing the porosity and beach. system. Other wave absorption capacity of the beach and  Increased potential of  No existing sites known of. encouraging sand deposition. nuisance wind‐blown sand. (SNH, 2000) PUBLIC AWARENESS Signs and Display Boards, Guided Walks,  Tourist sites where access is  Natural processes can  Vandalism of signage. Cornwall Public Talks, Interpretative Leaflets, Wardens restricted or schemes have been continue.  Gwithian to Mexico Towans. and Visitor Centres implemented which impact  Visitors with a greater  Perranporth. Provision of educational signs to explain the upon public use. understanding are importance of the dunes, why they require more likely to abide Other protection and how the implemented by notices.  Kenfig Dunes, South Wales.

Technique When Appropriate Benefits Problems Example Site

schemes work. This aims to make visitors  Sefton Coast Dunes. aware of why access is restricted and the damage which they can do by straying off paths.

At larger sites visitor centres can provide information with friendly wardens (voluntary or paid) to answer questions and monitor the dunes.

Can form an integral part of all dune management schemes.

(BTCV, 2005) Visualisations  Use of visualisations to support  Provides better  Visually presented Provision of visualisations of how coastal area community engagement clarity and information needs to be may change in the future. through scenario type planning understanding when clear understandable for approaches. communicating the audience, or could complex information. create confusion. Visualisations attract attention and can be more interesting for the audience. SEDIMENT MODIFICATION Beach Recycling and Reprofiling  All sites including those with  Low to moderate cost.  Ongoing maintenance Cornwall Mechanical movement of sand, shingle or limited blown sand available.  Accelerates natural requirements.  No existing sites in Cornwall. boulders from an area of accretion to an area recovery of foredunes.  Removes material from of erosion. Usually carried out over short  Provides short term other sites, potentially Other distances such as from an accreting dune ridge defence against single transferring erosion or  Thy, Denmark. to a blow‐out. Termed reprofiling when severe storms. environmental damage  Aberdovey to Tywyn, North material is transferred directly from lower to to donor site. Wales. upper beach or from dune crest to dune toe.

Technique When Appropriate Benefits Problems Example Site

 Could introduce beach Enhanced when used in combination with debris, non‐indigenous dune stabilisation techniques to prevent sediment and/ or erosion of unconsolidated sand (see vegetation thus risking STABILISATION). damage to local ecology.

(SNH, 2000) Beach Nourishment  High value amenity beaches.  Provides protection  Moderate to high cost. Cornwall Sand or gravel is imported to cover beach Beaches suffering erosion as a from erosion without  Ongoing maintenance  Par Sands. losses due to erosion. Schemes vary from a result of updrift defences or hard defences. required. few truck loads to repair a blow out to multi dredging works.  Enhances natural  Appropriate material may Other million pound schemes involving sea delivery  Effective for mixed sand/ gravel recovery and be unavailable or  West Coast of Jutland, of marine dredged material. beaches with moderate to high maintains the natural expensive. Denmark. value backshore assets. beach processes.  Dissimilar imported  Bjerghuse, Denmark. Usually implemented in combination with  Enhances the amenity material may alter the control structures such as groynes to reduce value of the beach. geomorphology or material loss. ecology of the site.  Sand blown inland may (SNH, 2000) increase in problem areas.

STABILISATION Planting  Sites with unconsolidated areas  Complements the  Dune fencing or Cornwall Planting of dunes to protect bare sand against of sand. natural system by thatching normally  Daymer Bay. deflation. Applicable to unconsolidated bare  Planting must be above normal enhancing natural needed for planting to be  Praa Sands. sand areas such as blow outs embryo dunes limit of wave run‐up to be dune recovery. successful.  Perranporth (Penhale Sands). and contoured dunes. Note that there is a successful.  Can be used to  Potential for complete distinction between vegetation which attracts enhance other loss of planting to a Other deposition for dune building, and vegetation management options. storm event.  Sefton Coast Dunes, England. which helps stabilise the dune surface.  Can be self‐sustaining. Different species will be required for different objectives. A wider range of species are

Technique When Appropriate Benefits Problems Example Site

appropriate for stabilisation than dune building.

Marram grass is most frequently used as it is able to withstand high burial rates.

(SNH, 2000; BTCV, 2005) Thatching  Sites with available blown sand,  Low cost.  Labour intensive and  No existing sites in Cornwall. The covering of exposed sand areas with where erosion is not severe.  Enhances natural requires ongoing cuttings from scrub thickets or forestry  Thatching must be above dune recovery with maintenance. Other plantations. Stabilises sand, reduces trampling normal limit of wave run‐up. minimal impact on  Without maintenance  Culbin Forest, Moreyshire. and protects dune vegetation. natural system. will last < 1 year.  Uses natural,  Materials often taken to Normally carried out in combination with degradable material. build bonfires. dune planting to increase stability.

(SNH, 2000; BTCV, 2005) Mulching/Matting/Sand Binders  Site with exposed sand areas  Low cost.  Binders can reduce  Daymer Bay (matting). Protects against wind erosion and reduces rain subject to erosion, where a  Enhances natural deposition by smoothing impact and splash erosion. Most useful in planting scheme is being dune recovery with the sand surface. Other combination with planting when they can implemented. minimal impact on  Some mulches may  Sefton Coast Dunes, England make significant improvements to plant natural system. contain seeds of alien (mulching using seaweed). growth.  Aids plant growth as plants.  Outer Hebrides (to stabilise part of combined  Matting subject to blow outs). Mulching includes the use of material such as stabilisation scheme. vandalism (pyromaniacs).  Southport, England. chopped straw, peat, seaweed, wood pulp or  Some stabilisers may  Binders can be damaged sewage sludge to cover the ground surface. have additional by trampling. properties such as  Maintenance required. Matting uses specialist materials pegged down releasing fertiliser.  Lifespan 1‐3 years or less to cover the ground surface, through which depending on specific holes are made to enable planting. Sand can product applied. be placed over the matting to discourage vandalism.

Technique When Appropriate Benefits Problems Example Site

Binders use chemical glues which create a ‘skin’ to hold the sand surface together. These methods can reduce sand deposition, but the improved vegetation growth more than overcomes this.

(SNH, 2000; BTCV, 2005) Control Fencing  Sites where planting and/or  Low cost.  Ongoing maintenance Cornwall To prevent access to planted/ thatched areas thatching have been  Enhances natural required.  Fistral Beach. (see also ACCESS MANAGEMENT) implemented, and access dune recovery with  Can be destroyed by  Sennen Cove. prevention is required. minimal impact on storm wave action.  Praa Sands. (SNH, 2000; BTCV, 2005)  Sites with high visitor numbers, natural system.  Materials often taken to where access to sensitive areas  Limits trampling and build bonfires. Other is restricted to prevent erosion of protected  Maximum life of about 5  Sefton Coast Dunes, England. problems such as trampling. areas. years depending on  Morfa Dyffryn. North Wales.  Encourages visitors to material, wave action keep to designated and vandalism. paths  Damaged fences can be visually unattractive.

3 Dune Management Preliminary Decision Assistance Tool User Guide 3.1 Introduction The Dune Management Preliminary Decision Assistance Tool was first developed as part of the Cornwall Sand Dune and Beach Management Strategy project (Halcrow, 2009). The aim of this tool is to help the dune manager identify potential management techniques that could help resolve problems identified in the dune system. This Tool will aid the decision making by providing a starting point for further work, however, more detailed scientific investigation is likely to be required to develop, design and implement the appropriate dune management technique. The tool has been updated as part of the 2015 Cornwall Beach & Sand Dune Management Plans project to incorporate additional techniques as described in Section 2 of this report. 3.2 Using the tool To use the Dune Management Preliminary Decision Assistance Tool, which is provided in an Excel Spreadsheet form in Appendix A, follow the steps at the top of the screen. Further information on the dune management techniques are provided in Section 2 of this report. A number of attributes can be chosen within each field, this will shorten the list of techniques that could be used until a single, or smaller range of appropriate techniques is identified. Not filtering an attribute will allow all cases to be considered. The range of attributes is outlined below. Issues addressed allows the user to define one of a wide range of various issues that can affect a dune site:  Beach Erosion – notable lowering of the beach levels in front of the dunes; this may occur for a number of reasons, including lack of sediment input to the system, or a storm event.  Blow‐out – areas of bare sand developed within the body of the dune system; while blow‐outs are a natural occurrence, their frequency is greatly exacerbated by human activities that erode vegetation cover such excessive recreational use, driving vehicles over dunes, the removal of sand for building materials or agricultural use.  Breaching – when seawater overtops the dunes, a channel may form; this usually happens during storm events or extreme high water conditions. Breaching may not always have a negative impact on a dune system – it is a natural process which, in unmanaged dunes, can occur occasionally and may not be detrimental to the health of the dune system.  Ecological Condition – when the ecological condition of the dunes, in particular with regards to targets of the UK Biodiversity Action Plan priority habitat features, is below desired condition grade due to presence of invasive and non‐native species, or is degraded due to human impacts (e.g. trampling).  Frontal Dune Erosion – loss of material from the front face of the dune system; this may occur for a number of reasons including wave action during storm events, high tide levels or strong winds. This can be a temporary or long term trend.

 Hinterland Tidal Flooding – usually as a result of breaching or outflanking. As with breaching, this may not always be considered a negative event, for example it may be necessary to maintain important salt‐water environments behind the dunes.  High Visitor Numbers – the effect of large visitor numbers on the dunes; commonly results in trampling, blow‐outs, vegetation loss and dune erosion.  Invasive and non‐native species – when invasive and non‐native dune species are present in a dune system. Refer also to ‘Ecological Condition’.  Litter/Pollution – the effect of large visitor numbers especially can lead to large amounts of litter and pollution on the beach and within the dunes. This can in turn have ecological impacts and impacts on overall quality of the area. Where on the dune denotes the location of the problem within the beach‐dune system. The possible options are:  Beach‐ below mean high water  Toe – at the seaward beach/dune interface  Middle – within the main body of the dunes  Back ‐ on the backslope of or behind the active dunes. Visual impact refers to the effect the techniques will have on the aesthetics of the dune system. The options are:  None – no change to the visual landscape  Low – a small change to the visual landscape but limited impact on the amenity value.  Medium – potential to impact on the visual landscape. Design needs to consider impact upon amenity value.  High – significant change to the visual landscape. High risk of impacts on amenity value of beach. Cost categorised as:  Low – £0 to £5k per 100m run  Medium ‐ £5k to £50k per 100m run  High ‐ £50k + per 100m run. Future maintenance refers to the frequency of maintenance required in the future, in order to sustain the technique:  None – no maintenance will be required  Low – maintenance will most likely not be required within a 10 year period  Medium – the technique will probably need some maintenance every 1 to 10 years  High – this technique will most likely require maintenance at least once a year. Life expectancy is the predicted life expectancy for each technique. This should be considered as a broad estimate; actual life will vary greatly due to differing environmental conditions:  Short – 0 to 5 years  Medium – 5 to 20 years  Long– 20 + years. Category relates to the type of technique employed:  Access Management ‐ controlling beach user access to protect vulnerable areas of the dunes;

 Adapt Backshore Management/Uses – adapting management and land use behind the dunes and allowing natural processes to continue;  Cease Existing Management – removal of management currently in place which is causing detrimental impacts on the beach and dune system;  Ecological Modification – maintain or improve ecological condition by cutting back or removing vegetation, particularly invasive and non‐native species;  Funding – seek to develop different sources of funding to enable wider range of beach and dune management activities to occur that are complimentary to each other;  Hard Protection Methods – construction of hard defences to manage erosion and/or flood risk;  Manual Maintenance – manual maintenance is focussed on efforts to reduce litter and other effects of large numbers of visitors (e.g. maintain fencing/signage) as well as ongoing measures to stabilise dune system (e.g. dune fencing etc);  Monitoring – regular surveys of the beach and dunes to assess short and long term trends;  Morphological Modification – managing the form and structure of the dunes;  Public Awareness – informing and educating the public;  Sediment Modification – managing the sediment available and/or location of sediment in the beach and dune system;  Stabilisation – stabilising unstable dune surfaces to reduce erosion and sand blow. Technique provides a description of each technique, along with a summary of when it should be applied. Associated benefits and problems can be found in Table 2‐1 of this report. A brief summary of each technique is provided here:  Access Management o Zoning – planning of the site to reduce or spread the impact of visitors. Encourage people to less sensitive zones and discourage people from sensitive areas. o Boardwalks – construction of wooden walkways through the dunes to reduce trampling and manage access. o Control Fencing – construction of fencing to prevent visitor access to vulnerable areas and contain traffic along designated access routes. o Use of information boards – use alongside defined routes through dunes, to provide explanation and information why to use the official route and not trample the dunes.  Adapt Backshore Management/Uses o Adapt Backshore Management/Uses – allow natural dune processes to continue but manage the backshore by moving/ replacing assets at risk and controlling future developments.  Cease Existing Management o Remove Defence Structures – hard defence structures along the dune front are of limited benefit in locations with a negative sediment budget and high wave energy. Such structures require significant maintenance and it may be economically and environmentally beneficial to remove them. o Cease Mechanical Litter Cleaning – mechanical beach cleaning can remove natural material which would normally encourage embryo dune growth. These methods can prevent embryo dunes developing and destroy young embryo dunes which have started to form.

 Ecological Modification o Maintain existing condition – this will vary from one site to the next, but could include items such as: ongoing regular maintenance such as cutting back; maintaining existing water levels in an area; maintaining any defences that control water levels; and allowing coastal processes to continue on maritime cliff/slope (no management intervention). o Improve existing condition – this will vary from one site to the next, but could include items such as: removal of non‐native invasive species within the dune vegetation; planting with additional vegetation, such as marram grass.  Funding o Seek funding from Environment Agency – this will be for coastal flood and erosion risk management related activities. o Seek funding from Local Authority – various funding streams from the local authority may be available to fund different aspects of management. o Seek funding from sole private source – private landowners/developers may wish to build their own defences or contribute to a wider partnership scheme to manage coastal flood and erosion risk. o Seek match funding (government+ third‐party) by establishing a funding partnership – a partnership funding approach that provides access to different funding sources to deliver a wider range of benefits of ongoing beach and dune management activities.  Hard Protection Methods o Sand Bag Structures – sand bags of various size used to construct reefs, groynes, headlands or revetments. Short‐term fixed defence. o Gabion Revetments – construction of revetment from wire mesh‐filled baskets filled with cobbles or rock. Provides short term protection by absorbing wave energy along the dune face. o Artificial Headland – construction of rock structures along the dune toe to protect vulnerable eroding areas. o Artificial Reefs – construction of shore parallel rock mound structures part way down the beach face. Structure dissipates wave energy protecting from erosion and encouraging deposition. o Near shore Breakwater ‐ shore parallel segmented structures along the upper beach at approximately high water. Reduces wave energy reaching the beach and dunes without affecting beach dune interaction. o Timber Groynes – cross‐shore structures made of timber which reduces longshore transport. Can be used to retain material in combination with beach nourishment. o Rock Groynes – cross‐shore structures made of rock that reduce longshore transport. Can be used to retain material in combination with beach nourishment. o Rock Revetments – rock used to armour the dune face. Dissipates storm waves and prevents further recession. o Timber Revetments – timber structures that can range from impermeable breastwork to temporary permeable upper beach wave barriers. Forms partial barrier to wave action when forming a permeable barrier along the upper beach or a wave protection wall when forming an impermeable vertical breastwork along the dune face.

o Clay Embankments – construction of clay defences to prevent hinterland flooding. Can be located behind the dune system to form a secondary defence. o Impermeable Revetments and Sea Walls – construction of a fixed line of defence across the front of the dune system.  Manual Maintenance o Beach/sand cleaning – undertake beach cleaning manually to avoid adverse impacts caused by use of mechanical methods. o Ranger/warden – presence of ranger/warden to provide regularly oversight of area and intervene when inappropriate activity occurs etc. o Friends of the dunes group – utilise ‘friends of’ type groups to support implementation of measures (e.g. beach clean events; dune fencing events; monitoring etc).  Monitoring o Monitoring – regular surveys of the beach and dunes to assess short and long term trends. Can include topographic surveys, LiDAR surveys and visual surveys. May be part of a regional monitoring programme. o Ecological condition – mapping coverage and condition of designated/ecologically important sites. o Ecological condition – mapping coverage of non‐native invasive species.  Morphological Modification o Dune Fencing – fencing designed to trap sand and encourage dune building. Can increase dune height and width, improving flood and coastal defence properties of the dunes. o Planting – planting of dunes with sand trapping species to encourage dune building. Can increase dune height and width, improving flood and coastal defence properties of the dunes. o Bulldozing/Contouring – bulldozing of existing sand to create new sand mounds or to infill blow outs. Reprofiling of existing dunes to a more stable aerodynamic shape. o Beach Drainage – burial of perforated land drain pipes below the upper beach which are connected to a pump and discharge. This lowers the water table in the swash zone, enhancing the porosity and wave absorption capacity of the beach and encouraging sand deposition.  Public Awareness o Signs and Display Boards, Guided Walks, Public Talks, Interpretive Leaflets – education of beach users to explain the importance of the dunes, why they require protection, the management in place and how the beach user can contribute. o Visualisations – use of visualisations to support community engagement through scenario type planning approaches.  Sediment Modification o Beach recycling and reprofiling – mechanically move sand from areas of accretion to an area of erosion e.g. accreting dune ridge to a blow‐out. Reprofile dune through movement of material from an accreting dune crest to an eroding dune toe. o Beach Nourishment – importation of sand or gravel to cover beach losses resulting from erosion. Can be used to raise beach levels or can be added to the dune system.  Stabilisation

o Planting – planting of dunes with species that help stabilise the dune surface to protect bare sand from erosion. o Thatching – covering of exposed sand areas with cuttings to reduce trampling and protect vegetation. Usually in combination with stabilisation planting. o Mulching/Matting/Sand Binders – methods to protect bare sand from wind erosion and reduce rain impact and splash erosion. Usually in combination with stabilisation planting.

References

 BTCV (2005). Sand Dunes – a practical handbook. Compiled by Brooks, A.; Revised Agate, E. BTCV, Doncaster, 109pp.  Carter R.W.G. (1988). Coastal Environments – An Introduction to Physical, Ecological and Cultural Systems of Coastlines. Academic Press, Cambridge, 617pp.  CH2M (2015). Coastal Change Adaptation Planning Guidance. Available online at http://lgacoastalsig.com/resources/coastal‐guidance‐and‐manuals/.  CIRIA (2010). Beach Management Manual second edition. CIRIA Report C685, Construction Industry Research and Information Association, 960pp.  Halcrow (2009). Cornwall Sand Dune and Beach Management Strategy: Sand Dune Management Techniques Report. Report produced for Cornwall and Isles of Scilly Coastal Advisory Group.  Pye, K. (2007). Sand Dune Processes and Management for Flood and Coastal Defence. Defra Project FD 1302.  Scottish National Heritage (2000). A Guide to Managing Coastal Erosion in Beach/Dune Systems. SNH, Scotland, 128pp. (available online at http://www.snh.org.uk/publications/on‐ line/heritagemanagement/erosion/sitemap.shtml).

Appendix A Dune Management Preliminary Decision Assistance Tool