Abstract
1. Some facts about Austria
2. Forest roads and alpine land management
3. Planning parameters of forest roads
4. Experiences in forest road construction
5. Harvesting
Otto K. SEDLAK
Director, Upper Austrian Forest Service
Linz, Austria
The paper briefly describes the Austrian forestry system in the context of the socio-economic and environmental setting. Main limiting factors of forestry are mountainous terrain, high labour cost, patterns of ownership, and environmental restrictions on harvesting.
A well-planned rural road network was recognized being essential for a sustainable land management and the multiple use of resources in Alpine country already in the early 1950s. Meanwhile a forest road net of about 100,000 km was constructed which became the basis of mountain forest management and utilization. The mean road density in commercial forests is around 45m/ha at present.
The author deals with some planning parameters and practical experiences in forest road construction on steep terrain. Limits of maximum road grades, employment of excavators instead of bulldozers, appropriate drainage, and immediate revegetation of road slopes are most recommended measures to minimize road-induced erosion.
The Forest Act and environmental regulations impose numerous restrictions on forest roading and harvesting in Austria. Since projects of forest roads need approval by the Forest Authority, for example, professional planning and supervision is compulsory in roading. Moreover, there are strict limitations for the size of clear fellings especially on steep slopes.
Harvesting methods mainly depend on forest ownership and vary from motor-manual felling to partly and fully mechanized systems. Mobile skyline yarding is one of the most preferred methods on steep terrain, but its share of about 15% of the total harvested volume is still rather low because of the relatively high cost.
Austria is one of the smallest but most densely forested countries in Central Europe. The country is landlocked and has no direct access to the sea. Neighbouring countries are Switzerland, Germany, Czech Republic, Slovakia, Hungary, Slowenia, Italy (clockwise from west).
1.1 Area, Topography, Climate
Total area: 84,000 sq.km
The orographic features are characterized by the Alpine mountain range stretching from east to west. There is a great variety of geological strata and parent rocks, e.g. granites, gneiss, schists, limestones, marls, sandstones.
The climate is moderate and transitional from continental in the east to maritime in the west. The eastern and northern regions of the country get a precipitation from some 500 to 800 mm a year, the western and mountainous regions get mean rainfalls from about 900 to 1,500 mm a year.
1.2 Population, socio-economic conditions
Population: 7.8 million, population density: 93 per sq.km.
Population in the economic sectors: 5% agriculture and forestry, 28% industries, 40% services, 27% pensioners and others. The total labour force is around 3.5 million.
Austria is not very rich in natural resources but has a well-developed economic and social system with a GDP of about US $17.300 per capita. While agriculture and forestry contributed 15% to the GDP in 1955, its share shrank to about 2% in 1993.
1.3 The forest resource
Forest land: 3.9 million ha (46% of the total area, 0.5 ha per capita). The forest area is steadily increasing by some 2,000 ha a year depending on afforestations of non-productive agricultural land. Boreal forests of mixed and/or pure stands of spruce, fir, pine, larch, beach, maple, oak, alder, etc. find good growing conditions. The timber line of the mountain forests is at 1,600 to 1,800 m a.s.l.
Commercial forests: 3.1 million ha (80%)
Protection forests: 0.8 million ha (20%)
Main tree species: 70% conifers (predominantly spruce), 30% broad-leaved species (mainly beech).
Mean standing volume: 300 cu.m s ob per ha in commercial forests.
Mean increment: 9 cu.m per ha annually.
At present, however, Austria's forest resource is underutilized because of economic and technical reasons. The current harvest is around 18-20 million cu.m, while the total increment is estimated at 31 million cu.m a year.
1.4 The forestry system
A regular forestry system commenced already in the Middle Ages under the early salt-mining and iron industry in order to produce mainly fuelwood and charcoal on a sustained-yield basis. Fossil energy and the modem railway and road system initiated the transition to timber production and forest industries not before a century ago.
Forest ownership:
· 53% small private forests (<200 ha)
· 32% private estates (>200 ha)
· 15% federal forests
Personnel:
At present, about 3,600 professional foresters are on the job in Austria. 50% are employed in the production sector of forest enterprises (mean value about 1,700 ha per capita) and 50% are in the service sector (Forest Service and other organizations).
Education and Training:
1 University, 2 Forester Schools, 1 School for Forest Guards, 2 Forest Training Centers for vocational and post-graduate training.
The labour force of forest workers shrank from 8,600 in 1984 to about 5,000 in 1993 because of mechanization and social changes.
Labour cost and productivity:
Cost of human labour has become expensive like elsewhere in industrial countries. The wage level of piece-rate work is around $13 per productive hour. Total cost is around $20 an hour allowing for non-productive time and social benefits. The productivity is about 1.3 cu.m/hour in thinnings and 2.1 cu.m/hour in final cuts of the Federal State Forests.
Figure 1. Typical land use and rural road net in Alpine country (source: Sedlak 1985).
About 70% or 2.8 million ha of forest land in Austria is situated within the fringes of the Alpine range in more or less steep terrain. Therefore, forest development and harvesting is limited by physical, economic, social, and environmental constraints:
· Difficult terrain: About half of the commercial forest area is situated on steep slopes exceeding 50%.· High labour cost: Labour cost in forest work is currently around $20 per productive hour.
· Ownership: About 60% of the commercial forest area is small private property dissected in small land parcels.
· Public constraints: Numerous legal restrictions on roading and harvesting.
On the other hand, alpine agriculture and forest harvesting are interdependent and rely upon a well-planned rural road network for a sustainable land management and the multiple use of resources.
A dense forest road net of nearly 100,000 km was constructed in Austria after World War II. The total road length within the forest land is around 140,000 km including public roads. The mean road density is 45 m/ha in commercial forests and 9 m/ha in protection forests including effective public roads.
The Forest Act contains numerous regulations concerning environmental effects of forest roads:
· Planning and supervision is restricted to professional foresters.· Restrictions of erosion control and watershed management must be considered especially in torrent catchments.
· Forest road projects need approval by the Forest Authority but may be subsidized from public funds, if they comply with the regulations.
Since the "Green Movement" got public support in the 70s, an additional environmental legislation with restrictions on forest roads exists in the provinces in order to protect nature and landscape.
3.1 Road Spacing
Road spacing and locally feasible skidding techniques are interdependent. Under Austrian conditions road spacing varies from 200 m to 400 m depending on steepness, forest ownership and available skidding equipment.
3.2 Road Alignment in Steep Terrain
While serpentine alignments are unavoidable in mountainous terrain, the number of switchbacks in a road course must be reduced to a minimum. Zig-zag roads with too short distances between switchbacks not only are ugly and difficult to travel but are sources of landslides and erosion on steep slopes. Therefore, cooperation between different small landowners in favour of appropriate road alignment is regarded compulsory.
Figure 2. Road spacing scheme for small private forests in Austria (source: Sedlak 1985).
Figure 3. Serpentine road alignment on mountain slopes (source: Sedlak 1985).
3.3 Practical Specifications of Forest Roads
|
Design elements |
Dimensions | |
|
Side slope |
< 50 % |
> 50 % |
|
Roadway width |
4.5 - 5.5 m |
4.0 m |
|
Single-lane width |
3.0 - 3.5 m |
3.0 |
|
Minimum radius |
25 m |
20 m |
|
Minimum switchback radius |
10 m | |
|
Min. switchback lane width |
6 m | |
|
Maximum grade |
9 - 12 % (16 %) | |
|
Minimum grade |
2 - 3 % | |
|
Switchback grade |
5 - 6 % | |
|
Turnout width |
3.0 m | |
4.1 Clearing width
While the clearing width of single-lane roads should not exceed 10 m on level or gentle ground, it tends to increase on steeper slopes.
|
Side slope |
Clearing width parallel to slope |
||
|
Cut section (m) |
Fill section (m) |
Total (m) |
|
|
< 40 % |
6 |
5 |
11 |
|
50 % |
7 |
6 |
13 |
|
60 % |
8 |
7 |
15 |
|
> 70 % |
10 - 15 |
3-4 |
13 - 19 |
Table 1. Backhoe work on steep ground (source: Sedlak 1982).
|
(1) Organic top soil is removed in front of the machine and spread on the rear fill slope in order to facilitate vegetative treatment. |
|
(3) Cut material is excavated and deposited in the fill, boulders are deposited on the lower bench as revetment. |
|
|
(2) A bench is excavated along the lower fill edge for better fill foundation. |
|
(4) Cut slope and subgrade are finally shaped. |
|
(SEDLAK 1982)
4.2 Excavator versus Bulldozer
The hydraulic excavator (backhoe) has replaced the bulldozer in forest road construction. While the bulldozer still is an economical option on easy ground, the excavator has improved the feasibility and quality of forest roads in steep terrain. The machine is very versatile, but training and professional know-how of the operator is of utmost importance for the result. Big boulders can be piled for retaining structures, excess spoil is loaded onto dump trucks to be hauled to deposit areas instead of being side-cast downhill. Organic topsoil is removed in front of the machine and spread on the fill slope in order to reduce erosion and facilitate an early revegetation.
4.3 Drainage
Provisions for road drainage are essential for road maintenance and erosion control.
Figure 5. Culvert with protective structures across a water course.
Depending on experiences in the Austrian Alps, the minimum diameter of normal cross culverts should be 40 cm rather than the usual diameter of 30 cm. At crossings with water courses environmentalists prefer fords against culverts, since the latter interrupt the water ecosystem. In critical torrents, however, a culvert for the normal run-off with a ford for high floods is recommended from the practical point of view.
4.4 Base Course
On weak, clayish subgrades the base course is the most expensive element of forest roads which needs around 3 cu.m of gravel per road metre and may cost up to 70% of the total cost. Long-distance transportation of gravel not only is costly but also is a heavy burden on access roads and the environment. Therefore, several material saving options should be considered depending on the local conditions:
· Recycling or processing of local material wherever feasible.· In cold climates the base should be constructed during frost periods to prevent subgrade deformation and to save costly gravel.
· A polypropylene fabric layer prevents clay intrusions between sub-grade and base course.
· Subgrade stabilization by means of quicklime.
4.5. Vegetative Treatment of Road Slopes
Early revegetation considerably reduces erosion. Therefore a vegetative treatment by means of hydro-seeding and mulching has become a standard procedure in Austria. Additional planting of alder and willows stabilizes wet and unstable road slopes.
Figure 6. Vegetative treatment of unstable road slopes for erosion control.
4.6 Roads along Water Courses
Water courses and their adjacent environs are sensitive and vulnerable. Therefore, forests on steep river banks are generally declared protection forests by the Forest Act in Austria. Moreover, environmental regulations prescribe buffer zones on both sides of rivers and creeks as well as around lakes in the provinces.
Figure 7. Buffer strip along a forest road.
Adequate buffer strips of 15 to 30 m width with silt traps from logging residues are required in roading and logging along water courses in order to protect them against erosion and sedimentation. Early cooperation of foresters with biologists and fishermen is recommended for well-adapted results already at the planning stage.
Also wet areas, e.g. bogs and swamps, are protected by the environmental legislation in the provinces and generally off-limits for logging.
The federal Forest Act restricts final cuts to stands over age 60 and clear fellings to certain areas depending on the forest type:
Clear felling limitations in production forests:
Strip clearcuts (mainly in mountainous areas): width < 50 m, length < 600 m (maximum area 3 ha).
Other clear fellings: Width >50 m, maximum area 2 ha.
Protection forests: Maximum clear felling area is 0.2 ha.
All clear fellings >0.5 ha need approval by the Forest Authority independently of the forest type in order to limit negative environmental effects on soil and adjacent forest stands. The system of harvesting and wood transportation is entirely based upon the dense forest road net in Austria. Direct timber transportation from the road landing to the mill prevails up to distances of about 150 km.
5.1 Timber Cutting
Motor-manual felling and bucking is common on steep slopes. On moderate terrain harvesters are employed especially in thinning operations and selective felling. The Federal Forest Enterprise developed a hydraulic processor for delimbing and bucking that can be mounted on a toolcarrier.
Harvesting systems in forest enterprises (figures rounded):
· 60% assortment method with motor-manual bucking,
· 30% mechanized full-stem method,
· 10% highly mechanized full-tree method.
5.2 Skidding and Yarding
The skidding methods show a great variety mainly depending on the type of forest property. While ground skidding by means of farm tractors with rear winch on moderate terrain and manual gravity skidding on steep slopes still are the most preferred methods in small private forests, forest enterprises and contractors employ the full range of modem machinery from special skidders to mobile yarders. Helicopter logging is too costly in Central Europe and, therefore, is restricted to difficult conditions and high value timber.
Applied skidding methods (rounded figures for 13 million cu.m in 1993):
· 60% ground skidding by means of wheel tractors and skidders,
· 15% manual ground skidding downhill (gravity skidding),
· 15% cable yarding mainly by means of mobile yarders,
· 6% forwarding,
· 4% miscellaneous.
As a rule of thumb, direct cost of yarding is twice as much as for ground skidding where both methods can technically compete. On the other hand, skyline yarding with fully suspended loads is one of the most preferable methods as far as the protection of soil and residual stands is concerned. Therefore, skyline yarding becomes competitive especially in sensitive areas, if costs of environmental damage are assessed. Various types of small and medium mobile yarders with automatic carriages for uphill and downhill yarding are produced in Austria. The average cable corridor length is from 200 to 400 m, the average load is around 2 t.
5.3 Landing, Loading and Hauling
Decentralized and rather small landings along the forest roads mainly at the junctions with skidtrails or cable corridors characterize the harvesting system in Austria. If the harvested timber cannot be stored at these junctions on steep terrain, skidders or farm tractors are employed for decking along the road in small quantities of about 1.5 to 3 cu.m per current road metre. Additional landings can be easily constructed at road curves across spurs. Larger landings exceeding 500 - 1,000 sq.m need a special approval by the provincial Environmental Authorities in order to control sources of erosion.
Timber trucks are operated by one driver only who is also in charge of loading by means of a mounted hydraulic crane with a capacity up to 5 t. The total weight of truck and trailer is limited to 38 t because of safety reasons and in order not to over-stress the public road net. There are no special hauling roads in Central Europe like in the U.S.
Literature Cited
Bundesministerium für Land - und Forstwirtschaft. 1993. Österreichischer Waldbericht, Wien.
FAO. 1989. Watershed management field manual. Food and Agriculture Organization of the United Nations, Rome, Italy.
Österreichische Bundesforste. 1993. Jahresbericht, Wien.
Sedlak, O. 1982 Types of roads and road network under difficult mountainous conditions and its relation to operational cable systems, ECE/FAO/ILO/IUFRO, Oslo.
Sedlak, O. 1985. Mountain forest roads in rural communities of Alpine Central Europe, IX World Forestry Congress, Mexico.
Sedlak, O. 1994. The utilization of forest resources and its influence on land use and watershed management in the Lirehsar Pilot Project Area, Mazandaran Province, Islamic Republic of Iran. Consultancy report prepared for the Food and Agriculture Organization of the United Nations, Rome, Italy.
Author's Contact Information
Otto K. Sedlak
Director, Upper Austrian Forest Service
Amt der o.ö. Landesregierung
Anzengruberstraße 21
A-4020 LINZ, Austria
Telephone: +49 732 6584 4660
Fax: +49 732 6584 4698
