technical article no. 9.2 accessways · figure 1: alignment of accessways that avoid funnelling of...

Accessways

Technical Article No. 9.2

INTRODUCTION

Vegetation is vital to the stability of foredunes as it trapsand anchors sand blown from the beach, helping to rebuilderoded dunes after storms. Damage or destruction of thevegetation cover on dunes often caused by human-usecan lead to wind erosion with loss of sand landward andthe lowering of foredunes. This potentially leaves foredunesas a less effective barrier against wave attack (BeachProtection Authority of Queensland, 1981).

To prevent damage to dune vegetation and to give anydamaged dune areas a chance to recover, it is oftennecessary to fence off the damaged or vulnerable partsof the dune systems and to provide formalised accesswaysor tracks from inland sites to the beach. This is especiallynecessary where human disturbance is likely to have asevere impact on vegetation cover on the relatively unstableseaward foredunes.

This article discusses the necessity and purpose ofaccessways on dune systems relating to human use,particularly pedestrian and vehicular traffic. It covers thetypes and designs of different accessway options. Thearticle also provides specifications for a range of designsand layouts, practical installation advice, and relative costsof different accessways.

Fencing to guide beach users is an essential componentof accessways and is briefly covered in this article as itdirectly relates to access. However, detail on fencingoptions and their construction is given in the DunesRestoration Trust of New Zealand Technical HandbookArticle No. 9.1. Te

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Seaward foredunes vs landward dunes

On the mobile frontal dunes, the design and materialsused in accessway construction must be adjustableso that the accessway can accommodate sandaccretion or erosion at the same rate as occurringon the adjacent parts of the dune. If accesswaysare not allowed to develop to the same height as

ROLE OF ACCESSWAYS

Accessways are used to allow pedestrians andvehicles access in a manner which protects boththe dunes and adjoining vegetation. While simplepathways through the vegetation cover exist onmost dunes to give access to the beach, it doesbecome necessary on moderate-to-high usebeaches to formalise such accessways to continueto provide access but at the same time protect thedune and vegetation from damage.

Formalising accessways generally refers to someform of fencing and signage to direct and confinethe movement of traffic. Some accessways mayalso involve wooden structures or other material forpedestrians to walk over. For most accessways, thedesign and construction requirements changealong the length of the accessway from the relativelyunstable seaward foredune to the semi-stablelandward dune.

the foredune, they create low spots which causewind funnelling and increased wind velocity whichresults in dune blowouts. Low spots formed inforedunes can also predispose the dune to increasedwave damage from high seas.

Although not always necessary, ‘sand ladders’ orboard and chain walks, that are maintained so thatthey remain on top of the fluctuating dune, haveoften been favoured for use on mobile foredunes asa flexible walkway in high use areas. These structuresthat can be managed to move with the fluctuatinglevels of the foredune to allow natural dune form andfunction to continue with minimal disruption. Incontrast, the semi-stable landward dunes are notlikely to require the same design and constructionspecifications to that of mobile foredunes.

Accessways over rear dunes are not likely to havemajor fluctuations in sand levels and therefore mayrequire only minimal input into the provision of anaccess track and maintenance. As with foreduneshowever, monitoring will be required to ensure thattraffic along the accessway does not lead to anywindblown sand erosion.

Options for managing access over unstable seaward foreduneswhere sand levels fluctuate (above) are different from accessways

through more stable landward dunes (inset).

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Article No. 9.2 - Accessways on dunes

Consultation and education

Constructing fencing or formalising accessways onbeaches is often not readily accepted by longtimeresidents or visitors to beaches. This is particularlyevident where there has been no or minimalmanagement of dune vegetation and access in thepast. However, with increasing pressure on ourbeaches and consequently increased destructionof dune vegetation and dune erosion problems,management of beach users in the form of fencingand formalised accessways is inevitable.

Management programmes of public areas, involvelocal communities and end users. It is essentialwhen implementing new strategies to provideinformation on the ongoing effects of uncontrolledaccess over dune systems on both vegetation coverand sand stability, and the advantages of agreedmanagement policies and actions.

Are accessways necessary?

Not all beaches will require formalised accesswaysto protect existing dune vegetation cover. Dunesystems with light usage are not likely to haveerosion problems associated with beach user access.However, as many of our beaches becomeincreasingly used for recreation, it is inevitable thatsome form of protection is required.

There are many examples where foredunes havebeen destroyed by uncontrolled access andindiscriminate use. Damage to dune vegetationresults from even moderately concentratedpedestrian or vehicular traffic. Without management,natural recovery can be slow or ineffective.

With loss of vegetation cover from trampling, winderosion can be severe and result in loss of sand,including scouring, leading to funnelling by prevailingonshore winds. This can lead to major blowoutswith sand deposited on vegetated dunes inland -all from a single uncontrolled informal pedestrianor vehicle accessway. These problems can occuron any dune system and can occur within weekson dynamic exposed coastlines.

Hard structures on dunes – a dilemma!

Dune systems, and in particular the mostseaward foredunes, are a flexible barrier of sandbetween the sea and the land. Dunes move upand down and in and out influenced by wave

and wind action. While appropriate sand bindingvegetation along foredunes acts to reduce these

effects, particularly of wind, such vegetationcover has evolved to work with the flexible natural

form and function of dunes.

Hard structures on foredunes and beacheshowever have a profound influence on the

way winds and waves move sand. While rockformations or headlands along sandy coastlinesnaturally affect sand movement, it is the effectof human-made artificial structures on dunes

and beaches that can significantly influence windand waves and in turn, sand movement andlevels on beaches and foredunes. There are

many examples of poorly designed andsometimes unnecessary structures on sandy

coastlines such as concrete drainage systems,seawalls, and dumped rocks that have resultedin major changes to sand levels and movement.

Construction of formalised accessways such aswooden steps and viewing platforms at or nearhigh water mark and over foredunes are hardstructures that will potentially influence sand

movement and natural dune form and function.Careful planning and care is therefore requiredin determining the objectives for such structuresand in choosing practical design options that

minimise impacts on wind and wave action ondune systems and beaches. This includes theuse of structures that are designed to have a

low wind resistance resulting in less accumulationof sand or scouring around large fixed objects.

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Location

Pedestrian accessways must be located at pointswhich:

are convenient direct access for beach usersfrom landward facilities such as carparks androad ends;

give maximum possible protection to vegetatedareas on the dunes;

are practical to ensure ease of construction andsafe access such as low sloping dunes withminimal risk of erosion;

are isolated from vehicle accessways whereverpossible, minimising chances of injury topedestrians; and

avoid high risk dynamic areas of dune systemssuch as near meandering river or stream mouths.

Where possible, accessways should be constructedwhere the public usually cross the dunes. Providingaccess at these locations will lead to greater publicacceptance of the role of formalised constructedaccessways.

A sufficient number of accessways will be requiredto cope with the numbers of beach users at thebusiest time of the year, usually the summer holidayperiod. If there are not enough formalisedaccessways provided, or they are not convenientlylocated, the public will inevitably ignore any fencingor signage and walk over dunes to the beach. Inmore isolated and low-use areas, only a smallnumber of accessways at greater distances may besufficient compared to higher use areas.

Existing informal tracks can give an indication of‘desire lines’ for establishing new or furtheraccessways along dunes to prevent damage to dunevegetation. Access points may need restoration suchas reshaping and planting with native sand bindersif foredune damage has been severe. Alternativelythe access track may need to be realigned to avoidthe worst areas of erosion.

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Uncontrolled pedestrian accessways can become majorerosion problems resulting in blowouts. The cover of nativesand binders spinifex and pingao are easily destroyed bytrampling allowing wind funnelling leading to blowouts andsand blown inland by onshore winds.

ACCESSWAY LOCATION AND DESIGN

Formalised accessways, including guiding fencesand the various options for providing material orstructures to walk on, can vary from simplifiedlow-cost construction to elaborate expensivestructures. In addition, careful consideration mustbe given to the location and alignment of accesswaysin order that they remain functional and do not initiateerosion.


Alignment and layout

Choosing the most appropriate alignmentand layout design for an accesswayacross the foredune is an importantconsideration (Figure 1). Whileaccessways aligned at right angles tothe dunes provide the shortest distanceacross the dune to the beach, this maynot always be the best option if prevailingonshore winds are also in the samedirection.

The aim should be to align the mostseaward section of the accessway atright angles to the direction of theprevailing onshore wind. Where theprevailing wind occurs at an angle to thebeach, a zigzag or angled accesswaydesign is likely to be more effective thanone aligned at right angle to the beach.Accessways aligned away from onshorewinds are likely to reduce wind funnellingand scouring of sand along the seawardface of the foredune of the accesswayand reduce accumulation of sand on theaccessway further landward. Angles inaccessways will be longer than straightroutes over the dunes to the beach andtherefore will require more designspecifications, materials and constructiontime.

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Beach-front property access

Accessways for beach front propertyowners can be problematic especially ifthere is an established culture of eachowner using individual tracks leadingfrom their property to the beach. Whiletraffic is usually considerably less thanpublic accessways, localised erosionespecially along the foredune can besignificant where these tracks exit ontothe beach at or near the high water mark.

Consultation with landowners, including discussion aboutlocalised erosion causing sand to blow inland andunderstanding movement of the foredune, is likely to leadto practical solutions that result in reducing the number oftracks across the dunes, and management to ensureerosion is not exacerbated. Sharing tracks or using nearbywell-managed public accessways are options that generallysuit most landowners.


Figure 1: Alignment of accessways that avoid funnelling of wind-blownsand from the prevailing wind will reduce erosion at the toe and up tothe crest of the foredune and reduce sand accumulation landward. Goodand poor options for the alignment and layout of accessways are shown.Aligning at least the seaward end of each accessway perpendicular eitherto oblique prevailing winds (above) or to direct onshore winds (below)is likely to require less maintenance compared to aligning entrances atthe foredune toe to prevailing winds.

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In high-use areas, it is usually preferable to use a capping railon fences either side of accessways, particularly along slopingsections. These can be used as handrails to steady pedestriansas they use the accessway. Inevitably, rails along fences willbe used for sitting and standing on, so sturdy wooden rails withposts at regular intervals will be essential to reduce injury, aswell as for maintenance requirements.

Ensure fences along accessways are placed immediately adjacentto board walks to prevent beach users creating erosion-pronebare sand tracks either side.

CONSTRUCTING ACCESSWAYS

Fencing

Fencing on either side of accessways isusually necessary in high use areas, astraffic, if not controlled, tends to divertfrom the track. This is particularly evidentwith pedestrian traffic that will often strayonto adjacent mature or establishingdune vegetation.

Often accessways are fanned out toallow beach users a convenient shortcutto the beach (Figure 2). This can lead toan embayment or indentation in thevegetation cover along the toe of theforedune, where a continuous cover ofnative sand binding plants just landwardof the high tide mark is most critical inmaintaining a naturally functioning dunesystem. When erecting fencing to guidebeach user traffic along accessways, itis therefore essential that fences do notsplay outwards at or near the seawardtoe of the foredune.

Figure 2: Accessways that end landward of the foredune toe encouragebeach uses to take short cuts that can lead to localised erosionproblems and even the formation of a significant indentation of thenatural line of sand binding vegetation along the toe of the foredune(left). Fencing along accessways should therefore be constructed tothe toe of the foredune to prevent this damage (right) and may requireat least short sections of fencing either side to help clearly demarcateaccessway entrances/exits.

Fencing that splays outward at the toe of this foredune hascaused a Y-shaped embayment along the seaward line of sandbinding vegetation, even though the sand ladder continues downto near high water mark. Fences should be taken to the edge ofthe seaward vegetation to prevent beach users taking short cuts.

Where there is a board walk or othermaterial provided for traffic use over thedunes surface, it is also essential thatfences are constructed immediately nextto these surfaces. A gap left between

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the fence and board walk can result in pedestrians selectingthese areas to walk and can cause differential scouring as baresand is blown away by wind.

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Slope

Construction of accessways with acceptable slopesis a major consideration as a large cross-section ofthe community will be using them (Soil ConservationService of NSW, 1990). Accessways should conformto the slope of either the existing dune or thereconstructed dune where dune reshaping of aseverely degraded foredune has been required.Flexible board and chain walkways can beconstructed on foredune slopes up to 25° (orone vertical unit to three horizontal units) forpedestrians but slopes less than this will be requiredfor regular vehicular traffic, especially in soft sand.

Surface materials

In order to protect accessways from wind erosionand the physical movement of sand downhill by feetor tyres, a protective cover is generally required onhigh use sites that permits ongoing access andprevents undue erosion (Soil Conservation Serviceof NSW, 1990). As discussed for unstable foredunesversus more stable landward dunes, differentmaterials may be used for providing a surface forbeach traffic, varying from board walks to woodchips or bark. Whatever material is used, it must beflexible so that it does not interfere with the naturaldune processes where sand levels fluctuate.

On many high use areas, wooden boards bolted tochains that are flexible have been used successfullyon fluctuating surfaces of foredunes, with wood chipor similar materials used on pathways on morelandward relatively stable dunes. However,increasingly, due to the cost of installation and theongoing commitment to maintenance, no surfacematerial is used and bare sand forms the surfaceof the accessway. This method is particularly suitableto less dynamic dune systems and relatively levelsituations where sand movement is not likely tooccur along the accessway.

Width

Depending on the site and intensity of use, pedestrianaccess tracks can vary from narrow tracks formedwithin the vegetation cover or if more formally fenced,to wider accessways that are likely to be more

practical if at least 1.2 m wide to allow two-abreastwalking. Wider accessways of at least 2.4 m widewill be required for vehicular access.

Revegetation around accessways

Most accessways are usually constructed wherethere is already an existing track over the dunes tothe beach. Continued uncontrolled access, especiallyin high-use areas, has usually led to degradation ofthe dune and vegetation cover to the extent thatmanagement is eventually required, involvingformalising the accessway.

Severely degraded sites may need reshaping butmost sites are likely to require planting with nativesand dune plants to repair areas either side of theconstructed accessway. This will help revegetateareas adjacent to the accessway that have beendisturbed by previous uncontrolled usage as wellas disturbance created by installation of theaccessway.

Boards can beeither half roundposts or 100 x 50mm timber boltedto galvanisedchain. Half roundposts can beplaced with roundside facing up ordown as preferredby the localcommunity.


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Bare sand surface

Increasingly, low maintenance options foraccessways over the mobile parts of dunes systems,even for high use areas, are being favoured. Theseare proving to be particularly successful on relativelysheltered beaches and where there are lowforedunes. Careful planning and layout of theseaward ends of accessways may obviate the needto provide alternative walking surfaces such asboard and chain structures, which are expensive toinstall and require constant maintenance.

Guide fencing, signage, alignment of the track exiton to the beach away from prevailing winds, andkeeping a narrow track within a good cover of sandbinding vegetation are likely to be practical lower-cost options to constructing a major board and chainwalkway. However, such bare sand walkways willstill require monitoring and where necessarymaintenance or even changes in alignment if sanderosion does become a problem.

CONSTRUCTION OPTIONS

Foredunes

Board and chain walkways

Board and chain walkways known as ‘sand ladders’are designed to adjust to the changing profile of theforedunes, thereby preventing the lowering of dunesalong accessways and the development of blowouts.Ease of access to and from the beach can beimproved particularly in soft sand and on foreduneslopes.

They are designed to be constructed from theseaward toe of the dune to the crest of the foreduneto provide protection and traction for pedestrians.Flat hind dune areas need not have board and chainaccessways.

When constructing pedestrian board and chainaccessways, ease of use is a priority, including thetype of boards used and spacing of boards that bestmeets beach user requirements (Figure 3).

While narrow spacing of flat boards may allow formore comfortable use by wheeled equipment suchas baby buggies, these will require more materialsand will be more difficult to keep on the surface assand levels fluctuate. These options tend to havesimilar problems to fixed structures on mobile dunesystems where they do not allow flexible movementof the dune profile.

Boards at narrow spacing, while necessary for wheeledtraffic, will be more difficult to maintain compared towidely spaced board and chain options where boardscan be more easily kept on the dune surface as sandaccumulates. Accessways with bare sand are proving to be relatively successful

especially for relatively sheltered low foredune situations.


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Sand ladders are constructed from timber and chain(Figure 4). The ladder is anchored landward of thedune with no anchorage seaward. This provides forsand movement and creates a ‘floating’ effect. Asprovided by Bay of Plenty Coastcare Leaflet No. 8,the method for establishing a board and chainwalkway is as follows:

Figure 3: Board and chain walkways are generally only required on the seaward face of the foredune in high use areas. They shouldextend from the foredune crest to the toe of the dune at or near high water mark. Landward of the crest, where dunes are likely to bemore stable than seaward parts of the foredune, a narrow track directly on the dune within dense vegetation is likely to be practical inmost situations, although other material such as bark or wood chip can be used on flat sections to define the track. Fencing will berequired particularly to guide beach users over seaward parts of the foredune and elsewhere where adjacent vegetation is likely to bedestroyed. Marker posts at either ends of accessways are effective in identifying formal tracks to and from the beach.

1. Wrap the end of the chain around the top of theanchor post. Attach each chain with at least twostaples.

2. Dig out any vegetation in the path of the ladder.Then level off the sand before running out thechain.

3. Bolt the first edged ½ round so it is level acrossthe slope (this is VERY important).

4. Use a 200 mm spacer to get the right spacing forthe steps. You may need to increase or decreasethe spacing on one side slightly to go aroundbends on the track.

Figure 4: Board and chain or ‘sand ladder’ showing the woodenboards used for the tread linked by galvanised chain usinggalvanised bolts. Half-round posts have been favoured at manysites but 100 x 50 mm planks can be used, provided edges aresmoothed to allow easy use with bare feet. Note that the sandladder is attached to posts at the landward end usually at or nearthe foredune crest while the seaward end is left to ‘float’ up anddown as sand levels fluctuate. Also note that the fences eitherside should be erected immediately adjacent to board edges toensure beach uses do not walk on sand either side of the boardsand thus create erosion problems.


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Solid boardwalks and steps

Solid wooden structures are only suitable for erecting on the more stable wellvegetated landward parts of dune systems to provide access. However,ultimately most will become undermined, damaged or completely destroyedby wave action during high seas or major storms.

Solid boardwalks or steps are notrecommended for the seaward end ofaccessways as these are highyvulnerable to erosion or exacerbatesand scouring. Beach levels can dropand seaward faces of foredunes canbe cut back several metres, even duringa single storm, leaving any structuresseverely undermined or completelydestroyed.

While solid boardwalks are favouredby beach users with prams orwheelchairs, expectations of providingthese structures over mobile foredunesare unrealistic. Nevertheless, boardwalks or low steps are found onrelatively sheltered beaches and lowforedunes.

Semi-stable dunes

Providing alternative surface materialto loose sand is not necessary on mostsemi-stable landward dunes (Figure5). Narrow sand tracks within a densecover of vegetation are often a practicaloption.

Fine bark, wood chips, metal or othersimilarly locally sourced material canbe used on flat areas to help delineatethe track on more stable parts of thedune system. Such material is alsolikely to be less susceptible to winderosion than leaving a bare sandsurface in exposed areas, especiallywhere adjacent vegetation cover issparse.

Choosing materials that maintain orenhance the natural aesthetics of the

Figure 5: Length of accessways will vary depending on proximity of carparksand road ends to the beach. Where carparks occur on or near the foredune,the short accessways over the foredune can comprise fenced angled tracks(left). Where carparks are located landward, accessways can be via a significantlength of track over undulating semi-stable landward dunes. A narrow bare-sand track within dense vegetation that may or may not require fencing islikely to be most practical leading to a fenced angled portion of track over theseaward face of the foredune (right).

location, are comfortable to walk on with bare feet, last reasonablywell, are cost effective to source and can be provided locallyare likely to be acceptable to beach users and the localcommunity.

Rigid materials such as asphalt, compacted clay and metal, orconcrete should not be used on any parts of the dune systemswhere they can be buried by wind blown sand, have the potentialto focus wind or waves that could exacerbate erosion, or wheresuch materials can be undermined and damaged by wind andwaves.

Solid wooden structures, whetherelevated boardwalks, viewing platforms,seats or steps, are best sited on thesemi-stable landward zones.


MONITORING AND MAINTENANCEIt is important that all accessways be regularlymaintained so that they continue to function correctlyand they do not become a hazard to public safety.Board and chain accessways with broken, splinteredor undermined boards require urgent repair as theycan cause severe injury to pedestrians and damageto vehicles. There may be a need to temporarilyclose public access to board and chain walks orother wooden access structures in the interests ofpublic safety if they are undermined by wave or winderosion.

In areas where sand is accumulating, board andchain walkways require lifting so that the boardscontinue to remain on the sand surface. If this is notdone regularly, the boards become so deeply buriedthat recovery without disturbing adjacent vegetationis extremely difficult and time consuming. In somesituations, deeply buried boarded accessways cannotbe easily recovered, thereby requiring completereplacement of the structure (Soil ConservationService of NSW, 1990).

Simple signs or posts at both beach andlandward ends of each accessway willencourage beach users to use formal accessroutes across dune systems. These can beas basic as a painted treated wooden postup to two metres tall erected on the back ofdunes at carparks or road ends with a smallsign indicating beach access. Similarly, aneasily identifiable post at the toe of theforedune clearly identifies access points backto landward facilities.

Over long stretches of sandy coastline thathave multiple entry points, some councilshave numbers or adjacent street namesrouted on posts allowing beach walkers toidentify accessways quickly. Keepingaccessway signage basic and low costreduces losses to vandalism. Posts at theseaward end can be easily lifted asthe dune increases in height or

EFFECTS OF CLIMATE CHANGEOver the next few decades, climate change effectsincluding sea level rise have the potential toconsiderably exacerbate hazard risk to coastalcommunities. The sea level has risen by 10-15 cmover the last century and projections are for thistrend to continue and to accelerate for centuries,with potential for a relative sea level rise of 50-80cm by 2100 (Ministry for the Environment, 2008).There will be more frequent and more seriousflooding of low-lying coastal margins by extremetides, storm surge and wave effects.

The potential for coastal erosion and flooding to beconsiderably accentuated by climate change effectsfurther emphasizes the importance of restoring andmaintaining wide natural dune buffers along theseaward margin of coastal development (Ministryfor the Environment, 2001). It is therefore essentialthat a good cover of appropriate native sand bindingvegetation is maintained on foredunes to ensurenatural dune building and repair after storms or highseas (Dahm et al., 2005).

With increasing development and usage of beaches,dunes inevitably become severely degraded and itis uncontrolled access that is one of the major causesof this degradation. Management of well-usedbeaches including establishment and maintenanceof formalised accessways is therefore critical in theprotection of both the natural and human use valuesof beaches, particularly in high-use areas.

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ACCESSWAY SIGNS

can be moved if the toe of the foredune becomeseroded landward or moves seaward.


REFERENCES

Authors: David Bergin and Michael Bergin, Environmental Restoration Ltd

Beach Protection Authority of Queensland, 1981:Management guidelines for dune usage.Pedestrian control fences, access tracks. Coastalsand dunes. Their vegetation and managementLeaflet No. V-02.1. 2p.

Coast Care Bay of Plenty Brochure No. 8: Sand ladders– getting you to the beach. Coast Care InformationBrochure No. 8. Coast Care Bay of PlentyProgramme, Whakatane. 4p.

Dahm, J.; Jenks, G.; Bergin, D. 2005: Community-based dune management for the mitigation ofcoastal hazards and Climate Change effects: aguide for local authorities. Report prepared forthe Climate Change Office, Ministry for theEnvironment. 11p.

Storms or high seas that result in significant erosion of the foredune can create majorchallenges for maintaining access, particularly where coastal dunes may be retreatinglandward naturally or where development is too close to the sea. If permanentshoreline retreat is not occurring and there is a well-managed dune of native sandbinding vegetation, natural dune repair is likely to occur over several months or morebetween storm events. This should result in the return of sand to the beach, the buildup of an incipient dune at or near high water mark, and a gentler sloping foredune.

Where this does not occur, there are no practical options for maintaining accesswaysover steep foredunes where there is likely to be continued erosion and significantchanges in the dune profile from further wave action or from wind. Alternativeaccessways either end of the most dynamic sections of erosion-prone foredunes islikely to be the only option in the short to medium term.

Ministry for the Environment, 2001: Planning forClimate Change Effects on Coastal Margins.http://www.climatechange.govt.nz/resources/reports/index.html

Ministry for the Environment, 2008: Coastal hazardsand Climate Change: a guidance manual forlocal government in New Zealand.http://www.mfe.govt.nz/publications/climate/coastal-hazards-climate-change-guidance-manual/html/index.html

Soil Conservation Service of NSW, 1990: Coastaldune management. A manual of coastal dunemanagement and rehabilitation techniques. SoilConservation Service of New South Wales,Sydney. Revised edition. 76p.

MAINTAINING ACCESS – AN EXERCISE IN FUTILITY!!!

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