A LITERATURE REVIEW OF THE ENVIRONMENTAL IMPACTS OF FOREST ROAD CONSTRUCTION

Raffaele Spinelli¹ and Enrico Marchi²

1 Consiglio Nazionale delle Ricerche, Istituto per la Ricerca sul Legno, via A. Barazzuolli 23, 1-50136 Firenze, Italy.

² Istituto di Assestamento e Tecnologia Forestale, Università degli studi di Firenze, via S. Bonaventura 13, 1-50145 Firenze, Italy.

Introduction

Good forest roads are crucial for effective forest management, regardless of its main objectives. Forest maintenance, wood harvesting, game control, recreational activities - all require the accessibility provided by a suitable road network.

However, road building is often regarded with suspicion because of its high potential impact. The new priority given to environmental protection involves a re-thinking of road building in both its general lines and its technical details. Providing access to the forest can no longer be considered one of the stages of wood production. Roads must be designed to satisfy multiple needs, and their construction must involve suitable practices to prevent environmental degradation.

Environmentally sound road building requires precise knowledge of potential impacts in any given set of conditions. Over the years, the subject has attracted a number of experts, who have studied the impacts of road building and have described a whole range of preventive and remedial measures. Since individual studies treat specific situations, a general perspective can only be obtained through a comprehensive review. This paper tries to set the framework for organizing detailed information. In the process, it defines the "pillars" of environmentally sound road building and points out the most urgent research needs.

Methodology

In 1995, l'Istituto per la Ricerca sul Legno (CNR/IRL) started the compilation of a worldwide reference collection on the environmental consequences of forest operations. This was meant to include all activities that constitute, precede and follow any harvesting plan, regardless of its characteristics. Therefore, clear cuts, thinnings, regeneration cuts are all included, as well as their accessory activities, like preparation, restoration and road building.

The work continued for more than a year. and was carried out within the scope of the European Concerted Action "Cost-Effective Early Thinnings" AIR2-CT93-1538. Fourteen countries participate in this concerted action, which therefore, has provided a broad forum for gathering, disseminating and discussing relevant information. The bibliography was completed in March 1996, and now includes 2560 references. It was published by the Danish Forest and Landscape Research Institute, and the raw database is available as a diskette at CNR/IRL.

All 14 countries participating in the concerted action contributed data and suggestions to the compiler. In particular, this collection incorporates large parts of previous collections, compiled by ARMEF (France), FERIC (Canada), INRA (France) and FVRP (Germany). However, the bulk of the data comes from direct consultation of Forestry Abstracts and Forestry Product Abstract, which in turn review over 400 serial publications.

The compilation covers a 15-year span, and takes into consideration that titles published before 1980 are either obsolete or have been included in earlier compilations. An exception was made for some specific works, in view of their lasting validity or of their importance as milestones in this field.

All selected entries contain ten descriptive fields concerning the approach of the study, its type, the medium concerned, the type and the consequence of the damage studied, the agent of the damage, the operation during which the damage happens, the region where the study is carried out, the type of stand and terrain. For each field, a limited number of codes were used in a rather rigid framework, which makes consultation easier. Indeed, the objective of the work was to provide a large collection of references, which can be subdivided into smaller universes for finalized consultation: finer analyses should always be based on careful reading of the selected works. In this perspective, the use of free-ranging keywords would have simply made consultation more complicated, without adding much to its informative value.

This paper demonstrates one possible application of this bibliography. Two researchers, one from CNR and the other from the University of Florence, have used the database to find all those titles that reported the code "road building" in the fields "agent of damage" or "operation considered". One hundred seventy-five references were found and extracted into a smaller database for further analysis. This has provided relevant information on the geographic distribution of the studies, the prevailing study type, and the kind of damage more often involved.

Finally, a printout of the extracted titles was produced and the original works, or their abstracts, were found in the respective libraries of the two institutes. Direct consultation of the original documents allowed drawing a finer review of the selected bibliography.

Characterization of the literature

The computer analysis yielded general information, which allowed us to map the broad characteristics of the bibliography available.

Regarding the type of work and its approach to the problem, roughly 80 percent of the references, 139 titles, are experimental studies. The collection also includes eight review articles and ten guides for the practitioners, whose purpose is to prevent or reduce the environmental impact of road building. In fact, prevention is the main purpose of over 40 percent of the works, whereas a good 50 percent deal with the simple evaluation of the impact. On the other hand, describing and evaluating the environmental impact of road building is not an end in itself, and most of these works aim at remedial or preventive measures.

Hydrogeologic impacts are those most extensively treated. Soil and water impacts represent the direct object of 154 references (88 percent). In particular, soil disturbance is considered the most important effect of road building (126 works, 72 percent), and erosion its most frequent consequence (119 works, 68 percent). Other hydrogeologic consequences complete a monochromatic picture (19 works, 11 percent). Only 5 percent of the works concern the impact on scenery, even if road building is believed to have important effects on the aesthetic value of forest landscapes. The same percentage applies to biodiversity, another of today's emerging concerns.

Mountain regions are very sensitive to hydrogeologic problems, and the strong focus on soil and water impacts corresponds to a very high representation of mountain sites (73 percent) among study locations. Temperate forests are the most studied (77 percent). The low representation of boreal forests (6 percent) is not surprising, since most commercial stands of this type grow on flat terrain. On the contrary, it is less understandable that very few studies (10) concern tropical forests. These are often mountain ecosystems, and the lack of studies may be just another example of the world's unbalanced development. This observation is supported by the geographic distribution of the studies; North America alone provides almost 60 percent of the titles. Europe, Asia and Oceania provide another 12 percent each. Africa and Latin America together are concerned by less than 3 percent of the studies.

Table 1. Geographic distribution of studies

Finally, a few lines about temporal distribution. Most studies were produced in the mid-1980s. Peak production was achieved in 1984; after that date, the number of publications undergoes a steady decrease. Comparative analysis has shown that such decrease occurred in all geographic regions, within a slight time lapse. The downhill trend began in 1982 for Europe, m 1985 for North America and in 1987 for Asia. Oceania alone was able to maintain a steady, yet limited, production.

The dissemination bias must be considered; older studies were circulated more than new ones, and are more likely to have reached the compilers. However, this might only mitigate our figure. The trend is so sharp that a possible bias is unlikely to bring substantial change.

Therefore, we are warned that in times of environmental concern and intensive land management, decreased attention to the impacts of road building may only mean that we are satisfied with our knowledge in this field, or that we are willing to take the risks implied by partial, ageing knowledge.

Table 2. Temporal distribution of studies

Impacts

The most studied effect of road building is hydrogeologic degradation, in the form of soil erosion, mass movement, sedimentation and altered stream flow.

Diffused soil erosion is among the most common consequences of road building. Erosion may concern all road elements - bed, banks, batter, fill and drains. The reasons why road building often results in accelerated soil erosion are the removal of vegetation cover, the loosening of soil and the creation of preferential routes to concentrated water run-off (Hattinger 1984).

The severity of the erosive phenomena depends on precipitation intensity, bedrock erosion, terrain morphology and road characteristics (Burroughs et al. 1984, Ezaki 1984, Hattinger 1984, Heinrich 1984, Kochenderfer and Halvey 1987, Lee 1995). Intense traffic results in increased erosion rates, which can be over 100 times higher than those recorded on low-traffic roads (Reid and Dune 1984). Much depends on careful planning and maintenance. According to McCashion and Rice, for example, one quarter of the erosion recorded on a 550 km sample of the Californian forest road network could be avoided using ordinary engineering practices (1983).

Road building can trigger the mass movement of unstable slopes (Amaranthus et al. 1985, Rood 1984). Once started, this process is very difficult to stop, and even reforestation does not guarantee its effective control (Lattusen 1984, Ma 1987). Prevention remains the best policy; careful planning and construction are crucial to successful road building. Indeed, road location and design play a major role in the occurrence of mass wasting phenomena, which are most likely to happen when the road is located on slopes steeper than 60 percent (Duncan et al. 1987, McCashion and Rice 1983, Sessions et al. 1987). These and other considerations have been integrated in a number of planning methods, which are often available as simulation programmes (Duncan et al. 1987, Hicks and Smith 1981, Sessions and Sessions 1991).

A substantial increment in sediment production is often associated with road building (Reid 1981, Pearce and Hodgkiss 1987) as a direct consequence of soil erosion and, especially, mass movements (Reid et al. 1981). Traffic intensity and road maintenance have the highest impact on sediment production (Reid 1981). The problem increases in the vicinity of streams. A road running directly along a stream can produce seven times as much sediment as a road protected by an undisturbed respect zone (Hattinger 1984). Several measures can reduce effectively sediment production; among them the establishment of undisturbed respect zones, the reduction of stream crossings, the maintenance of a good drainage system and the revegetation of road banks (Burroughs et al. 1984, Deki et al. 1988, Ellefson and Miles 1985. Patric and Kidd 1982, Swift 1984 and 1986).

In general, road building reduces soil infiltration capacity, increases water run-off and blocks natural drainage systems (Hattinger 1984). Rainwater is channelled along the road network and reaches its collector more rapidly than it would following its natural paths and increased peak flow is the general consequence of this mechanism, which can produce destructive effects (King 1989, Tilley and Rice 1977, Wright et al. 1990).

Besides hydrogeologic degradation, road building can produce other detrimental effects, especially on landscape and wildlife (Elgmork 1978. Gardner 1979). Different impacts are often connected; sedimentation, for instance, creates unfavourable conditions to fish survival and reproduction and, therefore, increased erosion is generally associated with a decline of aquatic fauna (Coates and Miller 1981, Hynson et al. 1982, Meehan and Swanston 1977, Mills 1980, Noggle 1978, Phillips et al. 1975).

Prevention

To reduce the environmental impact of road building, appropriate preventive measures are available for all three stages of the process, i.e. planning, construction and maintenance.

In general, road design must aim at serving the largest surface with the shortest road development (Gardner 1979). Routes must be selected that allow the minimum crossing of streams, unstable slopes and other sensitive areas (Hattinger 1984, Heinrich 1985). Planning must include the setting apart of undisturbed respect zones and the construction of a suitable drainage system. In particular, bridges and drains must be dimensioned for the highest expected peak flow (Sedlak 1982). Road width should be kept as small as possible in accordance with the characteristics of the expected traffic (Gaumitz 1990). Road paving has two edges and should be evaluated with care. While it is very effective in protecting the roadbed from erosion, it accelerates runoff and contributes to the increase of peak flows (Burroughs et al. 1984. Kochenderfer and Helvey 1987, Nowakowska 1987, Swift 1984).

Construction techniques and equipment have a strong influence on the type of impact and severity (Trafela 1987). Bulldozing is cost-effective, but it does not allow great accuracy. In steep terrain, hydraulic excavators must be preferred as they guarantee excellent work control, which is convenient when forming the fill or preparing the drains. As an average, excavator cost is 15-20 percent higher, but in sensitive areas this additional cost is largely compensated by reduced restoration costs (Gorton 1986). Construction should be followed by revegetation of the road banks, preferably with indigenous species (Ellefson and Miles 1985, Ezaki 1984). The success of direct seeding can be improved by the spreading of a mulch layer to protect soil and seed (Rothwell 1987). Otherwise one can resort to hydroseeding, whose complexity and cost ranges according to the local situation (Schechtl 1987).

Road maintenance plays a crucial role in the reduction of erosion and sedimentation (Yoho 1980, Douglas et al. 1983). Abandonment results in bank deterioration and increased sediment production (Orme 1990). Even a simple grading at the end of the harvesting season can yield substantial benefits since rutted roads produce twice as much sediment as levelled roads (Burroughs et al. 1984).

Conclusions

Effective forest management depends on the construction and the maintenance of an appropriate forest road network. Road building is essential to the multiple use of forest resources, and roads must be designed to satisfy a whole range of needs.

However, careless logging and road building are the main causes for the environmental degradation of most forest regions. In particular, road building can produce severe negative effects on soil stability, water regime, landscape quality and game population. The mechanisms that lead to these unwanted effects have been investigated in a number of studies, and a large corpus of knowledge is now available.

Implementing a number of measures during all three stages of the process (planning, construction and maintenance) can reduce the environmental impact of road building. In general, careful route selection, avoidance of unnecessary earthmoving and construction of an effective drainage system yield the best results. Road-bank revegetation and regular road maintenance are also crucial to good environmental performance.

The 175 studies reviewed provide further details on a broader range of practices. Unfortunately, state-of-the-art knowledge only concerns the western hemisphere and its temperate forests. Very few studies deal with the specific problems of road building in developing countries. More must be done to prevent their development from turning into environmental disaster.

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1985	BILBY RE	Contribution of road surface sediment to a western Washington stream.	For. Sci. 31(4);827-838.
1984	BOISE STATE UNIVERSITY	Project completion report - sediment yeild from cut and fill slopes - Silver Creek research evaluation, Boise National Forest.	Boise State Univ., Dept. Geolo. and Geophy., Cooperative Agreement, INT-80-003-CA.
1978	BROWN G.W.	Watershed management and the control of forest operations in the Pacific Northwest region of the United States.	Proceedings IUFRO 26.9-1.10.78 'For. Engineer. Dept., Oregon Sttae Univ. Corvallis Ore. 147-157, 32 ref.
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1984	BURROUGHS E.; WATTS F. J.; HABER D.F.	Surfacing to reducing erosion of forest roads built in granitic soils.	in 'Symposium of effects of forest land use on erosion and slope stability.', (O'LOUGHLIN C. L.; PEARCE A. J., editors). Univ. of Hawaii, 1984, pp. 255-264,12 ref, Honolulu, Hawaii.
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1985	BURROUGHS E.	Survey of slope stability problems on forest lands in the west.	In - Proc. of a workshop on slope stability - problems and solutions in forest management. (Swanston, D. ed), Seattle.
1983	BURROUGHS E., HABER DP, WATTS FI, KADOCH TL	Measuring surface erosion on forest roads and estimating costs of erosion control - preliminary results.	In - Low volume roads - 3rd inter, conf., 1983. Transp. res. Record 989. Was., DC. National Academy of Sci., Trans. Res.
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1987	CARR W W	The effect of landing construction on some forest soil properties: a case study.	FRDA Report (Victoria, B.C.), 1987, no. 003, vi+20 pp., 45 ref., ISBN 07718 85725, Canada
1988	CARR WW	Nutritional and soil compaction aspects of establishing forest cover on winter landings in the Fort St. James area.	Can. For. Ser., BCMOF, Vic, BC. FRDA rep. ISSN 0835-0752, #047, 6p.
1985	CARR WW	Restoring productivity on severely degraded forest soil in British Columbia.	Thesis, UBC, Canada 1985.
1983	CARR WW	Access road related degradation problems in forestry.	In: Proceedings of the 8th B.C. Soil Science Workshop, Harrison Hot Springs, February 17-18, 1983. BCMOF. pp 177-191.
1980	CARR WW	A handbook for forest roadside surface erosion control in British Columbia.	BCMOF Land management report LMR-4, Victoria, BC. 43p.
1978	CARSON W.W., DYKSTRA D.P	Programs for road network planning US Forest Service.	General Technical Report PNW-67. (1978)
1978	CASE A. B.; ROWE D. A.	Environmental guidelines for resource road construction.	Information Report, Newfoundland Forest Research Centre, 1978, No. N-X-162, v + 41 pp., 15 refs.
1983	CLAYTON J.L.	Evaluating slope stability prior to road construction.	Research Paper, Intermountain Forest and Range Experiment Station, USDA Forest Service (1983) No.INT-307, 6 pp., 14 ref.
1981	COATS R. N.; MILLER T.O.	Cumulative silvicultural impacts on watersheds: a hydrologic and regulatory dilemma.	Environmental Management, 1981, 5, 2, pp. 141-160, 51 ref., USA.
1993	COKER R.J.; FAHEY B. D.	Road-related mass movement in Wheathered Granite, Golden Downs and Motueka Forests, New Zealand: a note.	Journal of Hydrology, 1993, 31, 1, pp. 65-69, New Zealand.
1993	COKER R.J.; FAHEY B. D.; PAYNE J. J.	Fine sediment production from truck traffic, Queen Charlotte Forest, Marlborough Sounds, New Zealand.	Journal of Hydrology, 1993, 31, 1, pp. 56-64, New Zealand.
1990	COKER R.J.; PEARCE A.J.; FAHEY B.D.	Prediction and prevention of forest landing failures in high intensity rainfall areas of northern New Zealand.	in 'Research needs and applications to reduce erosion and sedimentation in tropical steeplands.' (ZEIMER R. R.; O'LOUGHLIN C. L.; HAMILTON L. S. Editors), IAHS Publication, 1990, no. 192, pp.311-317.
1983	COOK M. J.; KING J.G.	Construction cost and erosion control effectiveness of filter windrows on fill slopes.	USDA - Forest Service Research Note, 1983, 5 pp., Intermountain Forest and Range Experimental Station, Ogden, Utah, USA.
1989	CORNISH P.M.	Water quality in unlogged and logged eucalypt forests near Bega, N.S.W., during a nine year period.	Australian Forestry, 1989, 52 (4), pp. 276-285, 18 ref.
1981	COWEETA HYDROLOGIC LABORATORY	Summary of research results: the impact of forest management on water quality of mountain streams.	USDA Forest Service, 1981, Southeastern Forest Experiment Station, USA.
1988	DEKI T.; KANZAKI K.; FURUTANI S.; SUZUKI	(On the case of surface erosion on the steep forest road.	Bulletin of the Kyoto University Forests, 1988, No. 60, pp. 198-207, 5 ref.
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1993	DOUGLAS I.; GREER T.; BIDIN K.; SINUN W.	Impact of roads and compacted ground on post logging sediment yield in a small drainage basin, Sabah, Malaysia.	CSIRO Water Resources Series, 1993, no. 12, pp. 213218, 10 ref., ISBN 0643055770, Canberra, Australia.
1990	DOUGLAS I.; GREER T.; WONG W. M.; SPENCER T.; SINUN W.	The impact of commercial logging on a small rainforest catchment in Ulu Segama, Sabah, Malaysia.	in 'Research needs and applications to reduce erosion and sedimentation in tropical steeplands', (ZIEMAR R. R.; O'LOUGHLIN C. L.; HAMILTON L. S.; editors), IAHS Publication, 1990, No. 192, pp. 165-173, 9 ref.
1987	DUNCAN S. H.; WARD J.W.; ANDERSON R.J.	A method for assessing landslide potential as an aid in forest road placement.	Northwest Science, 1987, 61 (3), pp. 152-159, 18 ref.
1985	DUNCAN SH, WARD JW	The influence of watershed geology and forest roads on the composition of salmon spawning gravel.	Northwest Sci. 59(3); 204-212.
1978	ELGMORK K.	Human impact on a brown bear population (Ursus arctos L.).	Biological Conservation, 1978, 13 (2), pp. 81-103, 35 ref.
1985	ELLEFSON P.V.; MILES P. D.	Protecting water quality in the Midwest: impact on timber harvesting costs.	Northern Journal of Applied Forestry, 1985, 2 (2), pp. 57-61, 16 ref.
1980	EUBANKS S. T.	Full-restoration method for closing spur roads.	Journal of Forestry, 1980, 78 (10), pp 644-645.
1984	EZAKI T.	(Studies on the conservation of the face of slopes of forest roads.)	Bulletin of the Ehime University Forest (1984) No. 21, 1-116, 74 ref.
1986	EZAKI T, OGAWA S	A fundamental study on soil erosion and conservation of the face of slope of the forest roads.	College of Agriculture, Ehime University, 357 Tarumi, Matsuyama, 790, Japan.
1992	FAHEY B.D.; COKER R.J.	Sediment production from forest roads in Queen Charlotte Forest and potential impact or water quality, Marborough Sounds, New Zealand.	N.Z. Journal of Marine and Freshwater Research, 1992, 26, pp. 187-195.
1989	FAHEY B.D.; COKER R.J.	Forest road erosion in the granite terrain of southwest Nelson, New Zealand.	Journal of Hydrology, New Zealand, 1989, 28, 2, pp. 123141, 19 ref. New Zealand.
1988	FAHEY BD, COKER	Erosion and sediment production from forest roads in south-west Nelson.	FRI Private bag, Rotorua, NZ What's New, No 168 1988, 4p.
1979	FROEHLICH H. A.	The influence of clearcutting and road building activities on landscape stability in western United States.	in 'Forest soils and land use', (YOUNGBERG C. T., editor), Procs. of the 5th North American Forest Soils Conference, Colorado State University, August 1978, p. 165-173, 16 ref, Fort Collins, CO, USA.
1982	FUJII Y.; FURUTANI S.; SAKAI T.: SASAKI I.	(Development of rill erosion on the surface of forest road (II).)	Bulletin, Kyoto University Forests, 1982, No. 54, pp. 131-139, 2 refs.
1984	FUKUSHIMA Y.; KURODA Y., WATARI M.	(Discharge and sediment yield on forest road.)	Bulletin of the Kyoto University Forests, 1984, No. 56, pp. 145-154, 15 ref., Japan.
1982	FUSHIMI T.; FUJIHISA M.; OGAMI K.	(On the surface erosion of the forest road structure built by the earth work on the weathered granite region (II) Outflow and soil erosionat a model section of forest road.)	Bulletin of the Ehime University Forest, 1982, No. 19, pp. 13-19, 5 refs.
1979	GARDNER R. E.	Some environmental and economic effects of alternative forest road design.	Transactions of the ASAE, 1979, 22 (1), pp. 63-68, 6 refs.
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1977	GERMISHUIZEN P.J.; BADENHORST C. J.	The influence of harvesting on silviculture.	South African Forestry Journal, 1977, No. 102, pp. 29-36, 15 refs.
1985	GORTON F.	(Methods and costs of forest road construction carried out with regard for the landscape.)	Allgemeine Forstzeitung, 1985, 96 (9), pp. 241-244, 9 refs.
1987	GREY D. C.; JACOBS E.	The impact of harvesting on forest site quality.	South African Forestry Journal, 1987, No. 140: 60-66, 67 ref..
1993	GULLISON R.E., HARDNER J.J.	The effects of road design and harvest intensity on forest damage caused by selective loggig; empirical results and a simulation model from the Bosque Chimanes, Bolivia.	Forest Ecology and Management (1993) 59 (1-2) 1-14, 19 ref.
1981	GUNDERMANN E.	(The impact of forest road construction in the high mountain region of West Germany	Forstwissenschaftliches Centralblatt, 1981, 100 (2), pp. 65-75, 9 refs.
1978	GUNDERMANN E.	(Assessment of the environmental effects of forest roads in the high mountain region of West Germany. A study using the Delphi method.)	Forschungberichte, Forstliche Forschunganstalt Munchen, 1978, No. 41, vi+411 pp., 47 pp. of ref.
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1982	PESTAL E.	Forest road construction between economics and protection of nature	Etude FAO Forets no. 33, 1982, (HEINRICH R., editor), 'Exploitation des forets de montagne'.
1982	SEDLAK O.	General principles and planning of forest road-nets	Etude FAO Forets no. 33, 1982, (HEINRICH R., editor), 'Exploitation des forets de montagne'.
1982	JEDLITSCHKA M.	Torrent engineering works for the protection of mountain forest roads in the Region "Salzkammergut"	Etude FAO Forets no. 33, 1982, (HEINRICH R., editor), 'Exploitation des forets de montagne'.
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1982	HEINRICH R.	Road embankment stabilisation with biological and engineering works for forest roads	FAO Forestry Paper n.33:81-92
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1990	HELVEY J.D.; KOCHENDERFER J. N.	Soil density and moisture content on two unused forest roads during first 30 months after construction.	Research Paper Northeastern Forest Experiment Station, USDA Forest Service, 1990, no. NE 629, 6 pp., 3 ref, USA.
1987	HEMPHILL D. C.	A preliminary description of logging road construction practices for unstable soils used in the U.S Northwest.	Project Report - New Zealand LIRA, 1987, No. P.R. 31, xi+35 pp.
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1981	HICKS B. G.; SMITH R D.	Management of steeplands impacts by landslide hazard zonation and risk evaluation.	Journal of Hydrology, 1981, 20 (1), pp. 63-70.
1989	HICKS D. M.; HARMSWORTH G. R.	Changes in sediment yield regime during logging at Glenburvie Forest, Northland, New Zealand.	Proceedings of the Hydrology and Water Resources Symposium, 23-30 november 1989, pp. 424-428, Christchurch.
1990	HOWARD A. F.; KRIESE K.	Optimal road spacing for two-way grapple skidding to roadside in North Central British Columbia.	Transactions of the ASAE, 1990, 33, (3), pp. 1019-1023,4 ref.
1982	HYNSON J.; (ET AL.)	Handbook for protection offish and wildlife from construction of farm and forest roads; best management practices for building activities associated with the discharge of dredged or fill material.	USDA Fish and Wildlife Service, Eastern Energy and Land Use Team, 1982, No. FWS/OBS-82/18, 153 pp.
1977	MCNELLY J.A.	Planning forest roads and harvesting systems	FAO Forestry Paper n.2
1995	LEE H.K.	Soil erosion on the cutting slopes of forest roads.	Abstract of invited papers, in 'Caring for the Forest: Research in a changing world', (KORPILAHTI E., SALONEN T., OJA S., editors), IUFRO XX World Congress, 6-12 August 1995, Tampere, Finland, ISBN 951-40-1451-0, p. 46.
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1986	KIRBY M. W., HAGER W.A.; WONG P.	Simultaneous planning of wildland management and transportation alternatives.	TIMS Studies in the Management Sciences, 1986, 21. pp. 371-387, 39 ref.
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1982	LANGFORD K. J.; MORAN R. J.; O'SHAUGHNESSY P.J.	The Coranderrk Experiment - the effect of roading and timber harvesting in a mature ash forest on Streamflow yield and quality.	in 'First National symposium on forest hydrology', (O'LOUGHLIN E. M., BREN L. J., editors), Barton. ACT, Australia, Institute of Engineers, 1982, pp. 92-102, 10 refs.
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1981	LYONS JK	Influence of landslides, floods and land use on channel changes of the Upper Middle Fork Willamette River, Oregon,	Masters thesis, OSU.
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1982	MADEJ MA	Sediment transfer and channel changes in an aggrading stream in the Puget Lowland, Washington.	Proc. Sed. bud. and routing in for. drainage basins, USDA, Agri. for. Gen. Tech. Rep. PNW-141, pp 98-108.
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1987	MOHD BASRI HAMZAH, NIK MUHAMAD MAJID	Effects of soil compaction on growth of three- year old Acacia mangium Willd. Stand in Setul, Negri Sembilan, Malaysia.	The Malaysian Forester (1987) 50 (4) 250-257
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1980	MOSLEY M. P.	The impact of forest road erosion in the Dart Valley, Nelson.	New Zealand Journal of Forestry, 1980, 25, 2, pp. 184-198, 21 refs.
1991	MURPHY GE, BLUNDELL WM, FAHEY BD	Environmental constraints on forest harvesting in the Marlborough sounds.	FRI Bull For Res Inst New Zealand For Serv 1991; 166.
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1987	NOWAKOWSKA-MORYL, JADWIGA	(Stabilising the soil of forest roads with ashes in Poland)	Österreichische Forstzeitung 98(1987)H.6 S. 51-52
1985	O'LOUGHLIN	The influence of forest roads on erosions and stream sedimentation - comparison between temperate and tropical forests.	Working Paper, 1985, 28 pp., East-West Centre, Honolulu, Hawaii, USA.
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1981	STEELE KW, PRIEST RM	Soil and water values with particular reference to logging and roading.	Proc. LIRA, Rotorua.
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1984	SWIFT L. W. JR.	Soil losses from roadbeds and cut and fill slope in the southern Appalachians mountains.	Southern Journal of Applied Forestry, 1984, 8 (4): 209-216, 8 ref.
1984	SWIFT L. W. JR.	Gravel and grass surfacing reduces soil loss from mountains roads.	Forestry Science, 1984, 30 (3): 657-669.
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