Forest road design
Roger M. Hay
Forest Engineering Consultant
Edinburgh, Scotland, UK
The need for a Code of Practice rests on the marrying of the engineering elements of good road design with environmental, conservation and recreational requirements. The paramountcy of the road design is emphasised and the development of a consensus on the additional considerations of environmental affects on that road design are discussed. A clear set of guidelines for the frontline surveyors and road construction team is a basic requirement of any attempt at codifying roading practice.
Without road access most of the production of a forest would not be available. The construction of a forest road has the most potential of any forest harvesting operation to cause damage to the amenity and environment of the forest and, yet, is a most essential part of the strategic and tactical harvesting and other forest operations.
It is the need to fit these two contrary requirements that are the core of any forest road manual. It as necessary to ensure that all of the elements which go into the successful combination of
· a road which is right for the harvesting operation
· a road which is capable of safely carrying the haulage traffic
· a road which does not interfere with the natural drainage patterns
· a road which does not damage the landscape
· a road which takes account of the flora and fauna
· a road which can be satisfactorily and economically maintained
To do this requires an input from those involved with the preparation and implementation of the strategic and tactical plans for the forest area. They will include specialists in forest planning, landscape, conservation, harvesting, and engineering and may have additional input from fishing, game and soil specialists where required.
All of these people are experts in their own field, but unless they understand the reasons for the views of others, the various inputs could be counterproductive and result in a less than optimum solution.
As an engineer it is my purpose, in preparing a code of practice for the use of those who specialise in road building, to make sure that the principles of good road design and construction are paramount, but to take on board the need to have
· good landscape design
· road drainage design that deals adequately with demands of erosion prevention and fishing requirements, but does not compromise the absolute need to drain the road effectively
· road embankments and cuts which allow harvesting to take place without hindrance but which remain structurally stable
· cleared road widths which are minimal consistent with good road design and the ability if the sun and wind to reach the road to assist in drying
· the possibility of using the construction of the road to enhance the conservation environment. The change in soil structure arising from road building allows the growth of species which require that soil and the light arising from the tree felling on the roadline. Wildlife can also be encouraged with the changes in vegetation at the road edge. Good quality roads can add to the recreation potential of the area by allowing easier walking and cycling in parts of the forest previously closed and can allow easier game retrieval.
By providing a Code for such work which can be discussed with and agreed by all of the participants in forest strategy the need for discussion at the implementation level, is reduced Those who are actually building the road know the criteria on which the should proceed and against which they will be judged.
The increasing concerns of conservation bodies and the general public to changes in their environment, (and building of forest roads is certainly that), requires a framework in which the engineers who build the roads can operate and a Code of Practice which has been agreed and into which the input of engineers has ensured that the fundamental engineering principles have not been compromised is a way forward to prevent friction and to allow foresters to maximise their asset utilisation
It is interesting to see the development of the Code of Practice on Roads of the Forestry Commission of Great Britain over the years since its introduction in the early 1960's. Initially the document was primarily an engineering only road manual, describing the geometric, structural and hydraulic criteria to be used in the design and construction of roads. It had been prepared by engineers and was meant for use by engineers. Later changes were mainly involved in updating to take account if the changes in types of haulage vehicles and the influence of legal changes particularly in Health and Safety. By 1980 landscape had entered the Code and as the decade passed water guidelines and attention to the environment were introduced. Particular interest in recent years has been on the need for the road design to be geared to a maintenance regime which would be mechanically performed and minimise its affect on the environment.
There is always a tension between the natural desire to maximise the benefits of having an access road and the need to keep the basic engineering design in place. The use if tertiary roads for timber extraction is a case in point. To have any real purpose these roads must be very cheap to construct and are likely to be a bulldozer cut and not much else. The unfortunate consequences of poor drainage from such a track can be as serious as for a primary road and the lack of proper geometric design and surface metal compounds these problems. It is therefore questionable whether the real economics of poorly designed and constructed secondary and tertiary roads are fully judged. The difficulty is that once constructed it is extremely expensive to reinstate the pre road situation and the criticism of 'outsiders' is impossible to counteract.
It is, therefore, in my view, necessary to have a road Code of Practice that is applicable to all grades of roads and all of those involved in the approval of that Code must be aware that the influence of such a Code is likely to increase the cost of providing the road, but, if the Code is followed, the future savings in costs of maintenance and in the lack of consequent damage to the environment will offset those initial costs.
As a civil engineer I am anxious that the long understanding of good road design practice is followed in the design and construction of forest roads. The forest engineer who sets out the alignment of the new forest road must be aware of the requirements of all of the parties interested in the site, and the Road Manual or Code of Practice must contain sufficient advice to allow the engineer to be able to meet these requirements, in the main without further reference.
Civil Engineering Code (Forestry Commission of Great Britain, unpublished).
Author's Contact Information
Roger M. Hay
Forest Engineering Consultant
(formerly Director of Engineering,
Forestry Commission of Great Britain)
18 Cluny Place
Edinburgh EH10 4RL, Scotland, U.K.
Telephone: +44 31 447 2430