4.1 INTRODUCTION
4.2 BASIC DESIGN PRINCIPLES
4.3 LANDSCAPE DESIGN
4.4 ROAD LOCATION
4.5 VERTICAL AND HORIZONTAL ALIGNMENT
4.6 THE ROADLINE SCAR
4.7 ROAD MATERIALS
4.8 CULVERTS
4.9 BRIDGES
4.10 CONCLUSIONS
There is no doubt that the landscape is of vital concern to the majority of people. Rural landscapes are often perceived as unchanging, as 'natural' and as places to go to escape the stresses of city life. People care very much about the quality of the landscape and get very worried if changes occur which are to its detriment. A wide range of professions work in the countryside and many of their actions alter the appearance of the landscape. It is therefore important for the well-being of the landscape, for the satisfaction of those who love it and for its continual management that all activities - afforestation, buildings, utilities and roads - are well designed to fit into the landscape.
Successful design needs skill. It requires that those responsible for a development such as a new road understand how to evaluate the effect of their proposals on the landscape as well as they can evaluate their cost and functional efficiency. To do this an ability to 'read' the landscape is necessary. There is now a well recognised way of doing this, using a set of defined visual design principles. These principles allow us to analyse and describe the landscape and subsequently to design solutions which fit into it better. There are several major principles which are worth explaining before looking in detail at the methods of fitting roads into the landscape.
a. Shape
This has a very powerful influence on what we see. We pick out shapes often on the slightest evidence. Some shapes can be categorised as geometric, regular, artificial and man made while others are organic, irregular or natural. There are plenty of examples of geometric shapes in the landscape - early forests planted on hillsides, the surveyed grids used in field layouts, straight roads cutting across topography. By comparison organic shapes such as irregular natural woodland or sinuous curving roads seem to stand out less and be perceived as more compatible with the landscape around them.
b. Visual Force
When we look at a landscape our eyes are sub-consciously led around different parts of it in a pre-ordained way. It has been found that our eyes tend to be led up valleys, hollows and concavities and down ridges, spurs and convexities. Shapes which cut across or interrupt these flows or lines of visual force can produce unresolved, jarring effects which reduce the compatibility of that shape. A road cutting across a contour may fit less well than a more winding alignment.
c. Scale
The relative dimensions of the landscape and the amounts we can take in at one view determine its scale. Small elements can seem lost in large scale landscapes while large elements can dominate over small scale ones. Therefore it is important to work at the correct scale. This is complicated by the effect of different observer distances and between internal and external views, especially in forests.
d. Diversity
We respond positively to landscapes which contain certain amounts of variety. A landscape with very little diversity can be boring while one containing too much can be confusing. Additional elements can tip a landscape which is already very diverse into chaos.
e. Unity
Diversity has to be balanced against the need for unity in a landscape, where all the parts belong to the whole. An incompatible shape or an element creating a lot of contrast can fail to achieve unity with its surroundings and so look distinctly unhappy.
f. Genius loci or the Spirit of the Place
All landscapes are different although there might be general similarities. The sense of place is important to us in that it helps to identify a particular location and make it special. It is an intangible elusive quality easy to damage and difficult to repair. New elements introduced into a landscape should avoid damaging the genius loci and ideally should complement it.
Landscape design has been defined as "the organisation of a place in a way which reconciles the conflicting requirements of use while ensuring an attractive appearance".
It is fundamental to recognise that a good design is one which fulfils the 3 criteria of BEAUTY, UTILITY and EFFICIENCY. Each of these can be measured or defined to some extent. In the rural situation BEAUTY usually means adhering to the main principles outlined above, achieving unity, diversity and responding to the genius loci. Landscape design is not merely a cosmetic application to prettify something, nor screening or otherwise mitigating the worst effects of an ill-considered development. That is the province of 'landscaping' and is quite different.
Other papers in this conference will deal with the factors concerning utility and efficiency so the rest of this paper will deal with the visual quality part of the equation. It must be stressed that the 3 aspects should not normally be considered separately but integrated: this is really what design is all about. It is a process, starting with the objective of the development and the landscape it is to be placed in, achieving a mutually compatible solution.
At this stage we need to consider what the visual design objectives are likely to be when considering a new road development. In the countryside and particularly in wilder, mountainous areas, the qualities of naturalness are highly valued by our largely urban based population. Developments which contrast with this general character and more especially urbanise it are incompatible and should be avoided. The main aim should be to blend with the landscape and fit in with its character. That is not to say that certain engineering structures need be out of place or hidden. This partly depends on the scale, allowing the landscape to dominate, not the engineering structure. Sometimes the landscape quality can be enhanced by the contrast of a bridge spanning a ravine, for example some Swiss or Italian bridges in mountainous landscapes.
The first major decision which needs to be taken is the location of the road and the general route corridor. When choosing a roadline and surveying potential routes an appraisal of the landscape should be carried out. This may involve using sketches of photographs taken from significant public viewpoints and testing the impact of various general options. Computer analyses can also be used for this. The appraisal should include all factors to be taken into account, not only visual ones.
Important parts of a road alignment include those points where the road crosses a skyline; the geometry of the road at bends, hairpins and junctions; large-scale cuts, fills, culverts and bridges, all of which can increase the artificial qualities of the landscape, especially in close views. Natural qualities of the landscape should be reflected in the alignment. The aim is not to disguise the road but to reflect the scale and forms of the landscape in their design. If these factors are taken into account at an early stage the additional costs can be minimal with little or no effect on functional efficiency, yet the environmental benefits can be substantial.
The general location of forest roads should be planned to avoid important habitats and appear unobtrusive in the landscape. In agricultural landscapes access roads can be hidden behind hedgerows, dykes and walls or hollows amongst landform. Landscapes of particular quality or genius loci should be avoided, for example focal views, water edges and waterfalls. Watercourses of particular quality should be crossed at the least visible point. High standards of design and construction must be achieved in these sensitive locations.
The visible parts of the road should be in scale with the landscape, for example by not running close to the skyline for long stretches and avoiding routes which will result in large amounts of cut and fill in small scale, narrow valleys. The general alignment should run diagonal to the slope and not horizontally as far as technical constraints permit. Steeper slopes and summits should be avoided and skylines crossed at lowest practicable point, ideally in a hollow or saddle.
A road is a line in the landscape and its shape has a major effect on its appearance. The line should curve gently from side to side and up and down the slope. Straight lines in either direction tend to cut awkwardly across landform, especially where they conflict with lines of visual force. In order to blend with landform, roads should be deflected downwards on convex slopes and rise slightly in hollows and valleys. The degree of inflexion depends on the scale of the landform. Where this is large, generous curves are needed which will appear as simple engineering on the ground. In small scale landscapes over simple construction will obliterate landform detail if not carefully done.
In flat landscapes, especially in forests, roads have tended to be straight in the past. These can look artificial away from the built environment and can be daunting to walkers or cyclists. Curving alignments look more natural, taking advantage of any landform present.
The standard of the road determines the flexibility of the alignment. If the terrain is difficult yet the landscape is sensitive a lower standard may be the solution, for example reducing to a road capable of taking a 4-wheel drive vehicle instead of a car, or a tractor instead of a lorry. This is where a balance between all the objectives, environmental as well as functional, is necessary at the design stage.
Landings and turning points which require additional space should be located as far as possible where natural gradients provide more scope. Avoid prominent ridges. Hairpin bends and zigzag alignments on prominent slopes can look especially intrusive, made worse by large areas of cut and fill.
Cuttings and areas of spoil produced by road construction on steep slopes add further to the potential landscape impact unless dealt with sensitively. Geometric shapes, light, raw colours and their scale are the main factors to consider. Alignments should firstly be planned to avoid them if possible.
In soft rocks areas of cut should be excavated into more rounded banks to reduce the engineered profile, blend into the contours and allow vegetation cover to develop faster. In hard rock it is better to imitate natural crags with ledges and shelves capable of holding vegetation produced at construction. Occasionally an irregular combination of these 2 treatments can be used to break the artificial line of a long cut.
Vegetation cover is not always practical, but in open and prominent landscapes may be important to the extent of employing hydraseeding or turfing to accelerate its establishment. The right choice of seed and turf is important, in case a bright green line replaces a grey one in a landscape of subdued colour. In landscapes of more varied vegetation, extending the existing pattern on to the cut and fill will help. Material such as turf and bracken rhizomes can be saved at construction and re-laid afterwards if thought is given to the method of construction and there is room for storage.
In severely limited topography the impact of cut and fill together is so great that it may be better to remove all fill from the site. The cut is left but is probably more stable and easier to deal with than the loose, erodable fill in such circumstances. Obviously costs will rise in these cases.
Wherever possible road materials should be of local origin, ideally from the same location. This ensures that the colour and texture blend into the surrounding landscape. Brightly coloured or white stone can look very intrusive in many landscapes. Where the local stone is not suitable for the road then imported stone should be chosen for similarity of colour as well as for its cost and strength.
Where the road crosses a stream and a culvert is an appropriate method then the design will depend on its scale. A small concrete pipe can be set into the fill and collect the water while the slopes above are vegetated. Larger culverts, perhaps those constructed from Armco or similar material, require retaining walls in many instances. Gabions are one solution which can work well if arranged so as to emulate natural rock formations and filled with local stone. If stepped back vegetation can grow on the ledges which further help to blend them into the surroundings.
Where a stream has to be crossed by a bridge then further factors need to be taken into account.
a. Location
Siting a bridge should be very carefully thought out so that visual intrusion is avoided and genius loci protected. Because a bridge can be a substantial engineering structure in a fairly wild and remote location it should be sited away from rapids or waterfalls while providing a vantage point from which visitors may view them. A bridge can be a positive element in the sequence of experiences walkers may enjoy.
The alignment of the bridge to the river and the road leading to and from it should be designed so that there is a flow to it, across it and away from it. Cut and fill on the approach should be minimised and natural ground contours used wherever possible. The cut or fill around the bridge abutments should blend into the adjacent contours so that the bridge seems to grow out of the surrounding landscape rather than being placed upon it.
b. Bridge Design
The structure of the bridge itself needs careful thought. Concrete and steel can have a strongly urban feel while natural stone and timber relate more to the countryside.
Concrete is often a choice for cost and strength but smooth cast, light coloured abutments and wing walls are not compatible in colour or texture with natural settings. Alternatives include exposing the aggregate where local material is used; using shuttering to give texture and coloured cement to darken the concrete. Coarse vertical textures are most appropriate. Stone can be used to clad the concrete. One method is to build a stone face inside the shuttering and to pour the concrete in behind it. Large stones at the bottom grading to smaller at the top complete the effect.
Using gabions instead of concrete can be cheaper and more flexible, especially for the wing walls. The same considerations apply as for culverts. Timber abutments are widely used in other parts of the world and may have a place here.
The decking, its detail, finish and the way it fits the abutments needs care. Steel and concrete need the same thought as described for abutments. Steel beams should be painted in recessive earth tones. Timber decking is a good material. It weathers to a natural colour and is coarse in texture.
Handrails are to be avoided if possible. Where they are necessary for safety reasons their design should be simple and in scale with the bridge and the landscape. Chunky timber rails are likely to be the best. Tubular steel, especially with wire mesh infill looks urban, crude and fussy and should be avoided.
Many roads and their associated features have been put into the landscape in a careless and crude fashion. This has led to public concern. The advantage of low cost unsurfaced roads is that they are flexible in their alignment and choice of materials in a way in which most public highways are not. There is no reason why, with care and sensitivity it should not be possible to design roads to fit comfortably into any rural landscape where a road is appropriate and necessary.
Any construction site has the potential to cause pollution of one sort or another. When constructing a road, the main concern is pollution of watercourses. Such pollution can constitute real damage and it is therefor essential that close attention is paid to the control of water throughout all the stages of construction. Construction near streams, particularly fish bearing streams and those used for water supply, should be carried out during periods of dry weather. Before carrying out any work in a stream it is important to establish whether there are fishings, fisheries or water supply intakes downstream and, if so, to consult with the appropriate parties to agree any special measures to be taken such as timing the works to avoid spawning or agreeing emergency procedures in the event of accidental contamination of the waterway.
One of the potentially most serious causes of pollution on a construction site is the spillage of fuel and hydraulic oils. Proper care must be taken to keep fuel storage away from drains and to have robust systems in place for coping with spills. This should include the provision on site of oil absorbent materials and floating booms to contain oil in the event of a spillage. It is also important that plant be properly maintained and leaks of fuel or hydraulic oil be dealt with promptly.
