Book: Sand Dunes Chapter: 6 Access Management Section: Paths Metadata: Details Buy this book

GENERAL POINTS

• The simplest techniques are often the best. In the past, much effort and expense has gone into building boardwalks, which although very successful on some sites, have been costly failures in others, due to poor siting, design or lack of maintenance. A basic rule of thumb suggested from experience of the Sefton Coast Management Scheme is as follows. Where there is no sandblow, a surfaced path of gravel or chippings is suitable. In areas where accretion or erosion is in the range of 25-150mm (1-6") per year, adjustable boardwalks can be constructed. In areas of greater movement, from 300-900mm (1-3') per year, a simple mulched walkway provides an inexpensive access route which can be renewed or altered as necessarv (see below).
• Path construction is a time consuming operation, and it is well worth spending the extra money to buy good quality tanalised, or otherwise durable, timber for boardwalks, steps, and edgings to surfaced paths. The extra expense is outweighed by the advantages of having a uniform product which is easy to handle and join, looks good, lasts, and is usually respected by visitors. Cheap offcuts and unpeeled timber are difficult to use because of non-uniform size, they have a short life, and are more likely to be vandalised or used for firewood.
• Existing eroded paths can either be realigned or surfaced. When choosing an approach, remember to include maintenance as well as construction costs. Where a heavily used path is severely eroded, both realignment and surfacing may be necessary.
• Where you change a path alignment, indicate the new route by signs or fences and fence off or block the entrances to the old route with brushwood or shrubs. areas where the wind may be strong from various quarters should be taken through the dunes in an irregular zig-zag pattern, with each section no more than about 18m (20yds) long.
• Paths which receive moderate or heavy use should be at least 1.2m (4') wide, and 1.5m (5') wide, if possible, to allow people to walk side-by-side and to pass. If a path is too narrow for comfort, people will widen it or stray off it unless restricted by fencing.
• Pony tracks should normally be kept separate from pedestrian accessways. You may be able to restrict riders by signposting alone, but fencing along the length of the track is often necessary to keep horses in bounds. Often all that is needed is a single-strand plain wire fence on either side. The track should form a circuit for added interest.

ALIGNMENT OF PATHS THROUGH DUNES

• Paths through dunes should normally be angled obliquely to the direction of dominant winds, especially where these are on-shore, to reduce the risk of wind scour and blowout formation. However, on at least one site - Braunton Burrows NNR, Devon - paths are positioned in line with the wind, using slatted, movable duckboards (see Boardwalks), without erosion occurring. The wind can be used to advantage here to blow the path clear of drifting sand (Roberts and Venner, undated, p11).
• Where strong winds are not directly on-shore or where the dune system is rapidly prograding, paths should take the shortest possible route. This does not necessarily mean a straight line, since existing unplanned paths often wind slightly to cross firm slacks and to avoid high, steep dunes. The alignment of such paths should not be changed unless there are signs of serious wind funnelling and erosion along the route.
• Alignment is most critical where paths cut the windward sides of foredune ridges.
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  >Alignment is less crucial in backdune ridges of wide systems and where paths cross slacks.

• Paths which are intensively used or which cross areas where the wind may be strong from various quarters should be taken through the dunes in an irregular zig-zag pattern, with each section no more than about 18m (20yds) long.
• When choosing a new route through the dunes, there can be advantage in initially just marking the route and requesting people to keep to it, rather than investing straightaway in surfacing or boardwalk construction. The route can be marked with white painted posts, with some temporary post and wire fencing as necessary. This serves a dual purpose, firstly in showing whether the route is direct and attractive enough for people to follow it. Secondly, if people do keep to it they will trample the vegetation and start the process of path formation. Where it is required to keep people to one route, destruction of any vegetation followed by surfacing or boardwalk construction is usually inevitable. Where pressure is lighter, it may be possible to then encourage and maintain a trample-resistant sward by fertilising, seeding and periodic repair.
• Consider the routes that people may take if they don't find or avoid the start of the path from the car park, as they may find their way to the sea blocked by newly planted areas or fencing. If necessary make linking paths, or mark the main path clearly along its route with white posts so it can easily be seen. Avoid creating the situation where people can only turn back or climb through a fence, as they will almost certainly do the latter (see diagram in Car parks).

SURFACING

Choice of materials

• The best surface is one which is cheap and easy to apply and maintain and which looks in keeping with the surrounding terrain. In erosion-resistant areas such as dune slacks, and where use is so light that erosion is minimal, the existing natural surface is adequate, possibly aided by seeding and fertilising. Where artificial surfacing is necessary, its durability and replacement cost is as important as the initial cost of construction. For a detailed comparison of the use of various surfacing materials on one sand dune site, see Roberts and Venner (undated).
• Some sites have nearby sources of cheap surfacing material (eg shells) which should be exploited before other materials are brought in, even if only part of the path can be finished in the local product.
• Surfaced paths must be comfortable to walk on (preferably even for barefoot children) or else people will walk beside rather than along them. People also avoid timber walkways which have tilted due to shifting sand. Paths suitable for disabled people and pram-pushers must be made smooth and firm. But footpaths should not be too inviting to cyclists, for instance, since this makes them hazardous for pedestrians.
• Erosion or drifting is likely to occur where a hard-surfaced path runs out onto soft sand. Duckboards, which can be lifted and repositioned as necessary, are often the best choice here. Expanded-metal tracking is another possibility. Stone and other fixed materials are best limited to relatively stable backdune areas.
• Where permanent paths cross areas of tidal flooding, duckboards or raised boardwalks are necessary. Duckboards must be staked securely to keep them from shifting. Raised boardwalks are preferable since they can be used even at high tide and are less likely to settle unevenly. Tidal creeks should be avoided where possible and bridged where a crossing is needed. Bridge design is covered in the 'Foothpaths' handbook (Agate, 1983).
• Consider the environmental effects of surfacing materials before using them on sites of botanical interest. Fertilising and seeding, or the use of mulches, may promote rank grasses or introduce weed seeds along the path. Shells and limestone chippings may increase the alkalinity of the soil and encourage lime-loving plants to invade. Such changes usually affect only the immediate line of the path.

Grass

Natural vegetation, encouraged by fertilising and augmented if necessary by sowing with mixed native grasses, makes an ideal surface for paths through backdunes and slacks and over dune pastures which receive only moderate wear. Foredunes usually are unable to support species which resist trampling and so must be surfaced in other ways. See the chapter on Vegetation Establishment for information on sowing and fertilising.

The path must be closed off long enough for the vegetation to become well established. Where the path soil is compacted, aerate it before treatment using a light spiked roller. Where the soil is loose and dry, mulching is beneficial.

Mulch

On moderately used paths where the existing turf is worn or broken, or on heavily used bare sandy paths, a covering of chopped straw, mown vegetation from slacks, wood chips or bark peelings can be applied as a surface mulch. This helps hold the loose sand in place to make it easier to walk on, increases moisture retention, prevents sand blow, and slowly improves soil fertility to allow vegetation to recover. Note that bark peelings should be chopped and partly composted for this use; fresh, long pieces of bark can be slippery and uncomfortable to walk on. Of the available materials, straw and mown vegetation are best in dry sand because wood chips and peelings make more of a mess if they blow about. Chips and peelings are more useful in wet slacks where they help bind the sand and make walking easier.

Mulching is quick and easy and can be done while the path remains in use. Mulching can be effective for up to six to twelve months, according to exposure, but where use is heavier mulching may need to be done several times each summer as the material breaks down underfoot.

Shells

Shell paths, like those of stone, can be contained by edging boards if necessary, but they look better and are usually just as effective if left free at the sides to blend with the verges. Shell fragments make a durable surface which blends into the coastal dune environment and which can be added to easily as the need arises. Cockle shells are long lasting but oyster shells and mussel shells (the least durable) can also be used. They all break down into a fairly comfortable surface for walking. Shells should only be spread on bare areas since the aim is to supplement the vegetative cover rather than create an entire new surfacing. Shells increase the lime content of leached backdune soils and any vegetation which grows up during periods of low use may be more resistant to trampling than the original cover.

Shell waste is available virtually for free from shellfisheries. Because of the large amounts needed, it is best to get a lorry load and stockpile it. If shells are being dumped in the vicinity, you may be able to persuade the driver to distribute a load at convenient depots. It is better to have several small caches than one big one since this produces less stench as the shells rot clean and makes for easier distribution later.

Shell paths, like those of stone, can be contained by edging boards if necessary, but they look better and are usually just as effective if left free at the sides to blend with the verges.

Stones

Broken stones (gravel, chippings, quarry scalpings, hoggin or even fly ash or brick fragments) make a durable path in areas free from sand blow, but one which may look out of place depending on the colour and texture of the material used. The main thing is to build up a surface which is comfortable to walk on and not composed of sharp fragments. Ideally, you should grade the path in layers, with the biggest material at the bottom and the smallest on top. Firm each layer by tamping or rolling so that the large stones don't work to the surface with use. The most durable paths are slightly cambered to aid rain runoff. It may be necessary to build up the surface between board edging to prevent it being broken loose at the sides with use.

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Depending on the material used and the care taken, stone paths can last a long time with only minor repair. If some of the fine material is chalk or limestone the surface tends to bind together under pressure like concrete. At Braunton Burrows NNR, Devon, experimental concrete 'stepping stone' paths have been tried, but the results were poor (Roberts and Venner, undated, pp8-9).

Fabric

Various loose-weave fabrics, including fish netting, 'Wyretex', 'Terram' ('Cambrelle' with PRF 140) and 'Broplene' land mesh, have the ability to stabilise sand, support people and vehicles, and allow vegetation to grow through to help bind the fabric in place. 'Wyretex' is supplied by Malcolm, Ogilvie and Company Ltd, Constable Works, 31 Constitution Street, Dundee DD3 6NL; 'Terram' by ICI Fibres Ltd, Pontypool, Gwent: and 'Braplene' by Bridon Fibres and Plastics Ltd, Team Works, Dunston, Gateshead, Tyne and Wear.

Used fish netting may be available cheaply but much of it has too big a weave to be really useful. 'Netlon', a garden netting, has been tried at Braunton Burrows but was found to be too fine and could be dangerous to walkers (Roberts and Venner, undated, p9). All the special-purpose fabrics are expensive, but they are durable, relatively easy to handle, can be cut with shears and are easily staked in place, following manufacturer's instructions where given.

Fabric is best used in fairly flat areas where the turf is vigorous and unbroken so that grass grows up through the netting and anchors it in place. Where the surface is bare, sand tends to shift under the fabric so that it rolls or bunches up, or else the sand drifts over the top, making the path difficult to follow. Where the turf is open and slow growing, the fabric tends to shift slightly when walked on which damages the plants. Staking is important to minimise this problem and to provide a taut surface which conforms to the contours and is safe to walk on. Fish net and 'Broplene' tend to stretch with use, making periodic relaying essential, so that these fabrics cannot be fixed permanently or secured against theft.

Metal tracking

At some sites used for military training, such as Braunton Burrows, Devon, sections of expanded-metal track with bitumen underfelt may be available free or nearly so. The tracking is ugly, and the felt collects rain water, but it lasts indefinitely and makes a wide path (about 3m, 10') which can support vehicles. Sommerfeld tracking, which consists of wire netting reinforced by rods and edging bars, lacks the underfelt but has similar uses. This is available from Sommerfeld Flexboard Ltd, Doseley Industrial Estate, Frame Lane, Doseley, Telford, Salop. Both types of tracking are normally held in place by 600-900mm (2-3') long metal pickets.

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