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6. Guidelines for Roading and Watercourse Crossings

6.1 Roads
6.2 Watercourse Crossings
6.3 Log Pond and Wharf
6.4 Quarries


To plan extraction systems that are safe and economical.

To minimise the loss of productive forest area.

To minimise sedimentation of watercourses.

To minimise disturbance to excluded areas.

To provide and maintain good surface and side drainage during and after construction of roads and other infrastructure.

Regardless of the type of harvest system used, pre-planning of the log extraction system will result in lower costs and less environmental and social disturbance than without effective planning.

6.1 Roads

6.1.1 Road Classification

Major roads

Major roads are those that can carry trucks with large log volumes (e.g., 2,500 m3 or more per week averaged over the logging operation).

Minor roads

Minor roads are those that can carry trucks with moderate log volumes (e.g., between 1,000 and 2,500 m3 per week averaged over the time that they are in operation).

Haul tracks

Haul tracks are those that can carry trucks with small log volumes (e.g., less than 1,000 m3 per week averaged over the time that they are in operation).

6.1.2 Road Design


Roads should be designed in locations according to the following:

Forest Authority should be responsible for the co-ordinated development of infrastructure including location of roads;

a Forest Authority Officer must approve the roadline prior to commencement of construction;

locate roads in areas of low side slopes;

locate roads so that no earthworks or soil spill falls into watercourse buffer areas (Figure 6-1);

minimise the number of watercourse crossings;

balance cuts and fills to minimise transport of road construction material;

in swamp forests, roads are inappropriate in most cases, so temporary railway systems (or other similar low-impact transportation systems) located on a grid pattern should be planned for log extraction.

Areas to avoid

Areas where roading should be avoided are:

areas excluded from harvesting (if unavoidable, approval must be received from a Forest Authority Officer);

locations that require box cuts;

areas subject to flooding;

steep and unstable areas:

- gullies,
- swamps and mangroves,
- wetlands/watercourses,
- conservation/reserve areas.
Suggested maximum side slopes


Suggested maximum batter slopes


(This will be on moderately stable soils.)

Road grade specification

Road class

Preferred maximum allowable grade (%)

Preferred maximum adverse grade (%)

Preferred maximum length at maximum grade

Major road



1000 m

Minor road



750 m

Haul tracks



600 m

Steeper grades (up to 20%) for short sections (maximum 500 m) would be acceptable if this reduces the disturbance from road construction.

Any two sections of road at absolute maximum gradient should be separated by 100 m of level or lower gradient.

Roading width should be kept to a minimum but will depend on the truck width and travel speed.

Road widths

Suggested maximum road widths are:

Gravel Surface

Compacted Clay Surface

Major road (2-way)

10.0 m

15.0 m

Major road (1-way)

6.3 m

11.0 m

Minor road

6.0 m

7.3 m

Haul track

5.0 m

6.0 m

Road off-tracking

Curve widening will be required on corners to allow for off-tracking of trailers. Recommended road curves and widening of corners to allow for off-tracking on all road classes are:

Off-tracking on curves (metres vs radius of curvature) based on a vehicle with overall length of 14 m

Radius (m)




















NOTES: Additional width is required in each lane, ie a two-lane road requires a total widening to the roadway width of twice the tabulated value.

Fit curves to the topography. The minimum radius of the curve is related to visibility and the speed of vehicles will be travelling on the road. These are shown in the table below.

Design speed

30 kph

50 kph

80 kph

Minimum radius (use may require signs)

25 m

30 m

55 m

Desirable minimum radius

35-75 m

75-120 m

140-300 m

Minimum sight distance required

30 m

64 m

120 m

Meeting sight distance

50 m

100 m

220 m

Figure 6-1: Road Location and Drainage

6.1.3 Road and Haul Track Construction

Timing of constructions

Preliminary roadline clearing should be undertaken well ahead of final construction in any one site to reduce sedimentation from undrained sections.

Major and minor roads are to be completed well before logging.

Construction is not to commence more than 12 months before harvesting.

Survey requirements

Survey and mark the centreline of roads and haul tracks on the ground using the defined specifications.

Locate obligatory control points.

Locate log landings.

Roadline development

All merchantable stems are to be felled and extracted along the road alignment.

All clearing debris is to be heaped and burnt within the area of roadline (or roadside log landing if this is included in the harvesting plan).

Organic debris should not be used as fill.

Soil heaps, berms and debris stockpiling along roadside is prohibited.


These are tracks constructed to allow machinery to gain access to an area ahead of the main construction activity.

They are not generally permitted. Their location and justification should be discussed in the harvesting plan. A field inspection by the Forest Authority Officer is suggested before approval is considered.

Where a temporary track is approved, it should be:

- sited so as to avoid felling trees greater than 30 cm dbh;
- less than 4 metres wide;
- stabilised, with cross drains constructed immediately after use has been completed.
Road and haul track drainage


Drain all roads to minimise sediment production. Road drains should be constructed as follows:

- at changes of slope;
- within 50 metres of watercourse crossings;
- additional drains as needed to stay within the maximum spacing requirements.
Side drains that are adjacent to roads that have been box-cut should have rock bars at half the maximum drain spacing.

Indicative drain spacings used in Asia and the Pacific are as follows:

Centreline gradient (%)

Maximum drain spacing (metres)

Unstable Soil

Stable Soil













It is suggested that roads should not built with grades exceeding 18%. Maximum truck grade is about 23%.


The following suggestions are made to promote suitably drained roads and haul tracks:

Concave road surface should be maintained at all times.

The installation of culvert pipes, and minimum earth fill over them, should be in accordance with manufacturer's guidelines (e.g., 600 mm for reinforced concrete pipe).

Culvert pipes should be a minimum of 600 mm below the apex of the road surface at the time of construction (Figure 6-2).

Side drainage for table drains. Side drain grade is 1-3%.

Where high-water flow velocities are expected in high and very highly erodibility soils, drains may require special treatment such as lining with stones, concrete, grass etc to reduce scouring.

Where unacceptable erosion of a road cutting face is likely, catchdrains should be constructed along the top sides of the cuttings to collect surface run-off. Such drains should be gently graded and/or protected against scouring, particularly in the more erodible soils.

Table drains should be dish-shaped and constructed to a minimum depth of 300 mm below the level of the top of the formation at the outer edge of the shoulder.

Adequate provision will be made at culvert inlets and outlets to minimise erosion being caused by flow entering or discharging from the drain.

Adequate provision of sumps or silt traps will be made to prevent siltation and blocking of culverts in high and very highly erodible soils (Figure 6-3).

Culvert pipes should be laid on a grade of between 1% and 3% to minimise silting up of the pipes and excessive scouring at the discharge end.


Drains are not to directly enter watercourses but should be diverted into surrounding vegetation at least 50 m before a watercourse.

Figure 6-2: Road and Haul Track Drainage Construction

Figure 6-3: Silt Traps on Drains

Major and minor roads

Roads are to be located on elevated areas wherever possible to minimise side cutting, width of clearing and drainage problems.

Where side cutting is necessary, cuts are to be formed as shown in Figure 6-4.

Where side cutting is not necessary, earthworks should limited to the width allowed for the pavement plus verge and table drains on either side. An additional width to allow for travel by track machines may be approved following inspection by the Forest Authority Officer. Approval must be received before felling and clearing commences.

Surfacing material can be coral, crushed rock, compacted clay or gravel.

Figure 6-4: Major and Minor Road Construction

Haul Tracks

Haul tracks are to be located on spur lines (ridges) wherever possible to minimise side-cutting and drainage problems.

Side-cutting should be formed as shown in Figure 6-4.

Where side-cutting is not necessary, the width should not exceed that specified for the travel surface.

Revegetating cut and fill areas

Revegetation should be undertaken and can be carried out using a range of measures such as cereal cover crop (e.g., rice, millet), grass or seed of fast-growing shrubs or trees immediately after construction.

Limits to road construction

Wet weather restrictions apply.

Road construction should not occur during the wet season.

Road maintenance

All drains, pipes, culverts and bridges are to be kept open at all times. They are to be inspected thoroughly and repaired before the onset of the wet season/monsoon and during periods of heavy rainfall.

Removal of soil from the surface of roads, except during initial construction, is not permitted.

Road surface maintenance should be performed as needed. Crossfall and road shape should be maintained to allow effective drainage.

Good surfacing gravel should not pushed to the road edge or into drains.

Road closure and rehabilitation

Consultation with local stakeholders should be conducted prior to deciding on road closure. All feeder roads approved for closure should be decommissioned and rehabilitated.

Remove log culverts and temporary bridges to allow unobstructed waterflow (Figure 6-5).

The road surface should be maintained intact so the road can be reopened when required.

Cross-drains (Figure 6-6) should be installed at the following density.

Road gradient

Space between drains


Nil required


120 m


80 m

Figure 6-5: Removal of Temporary Bridges to Minimise Impact on Stream Flow

Figure 6-6: Cross-Drain System

6.2 Watercourse Crossings


To provide permanent bridges or culvert crossings (to be retained after harvesting) over all watercourses crossed by roads, constructed with durable materials.

To provide temporary bridges or crossings in areas where roads will be decommissioned after harvesting.

To restrict disturbance to watercourses and surrounding buffer areas to that necessary for crossings.

To minimise sedimentation of watercourses.

6.2.1 Types of Crossings and Uses


Bridges should be used for road crossing of all Class 1, 2 and 3 streams (except where fords are acceptable). They may also be used to cross other watercourses.

Culverts or pipes

Culverts or pipes should be used for crossing gullies and waterways (if bridges are not used). FAO Watershed Management Field Manual Guide 13/5 provides details for culvert sizes.

Fords/low-level crossings

Fords are acceptable when:

bank height of the watercourse is less than 1 metre;
depth of normal waterflow across the ford is less than 0.5 metre;
approaches to the stream are less than 5° (10%);
the bed is solid (gravel or stone), with rock accumulation downstream.
Temporary bridges

Temporary bridges may be used for roads after harvesting.

Log clusters with earth fill

Log clusters with earth fill should NOT be permitted for any watercourse in any situation.

6.2.2 Construction of Watercourse Crossings


The location of all watercourse crossings is to be inspected and approved by the Forest Authority Officer prior to construction. The chosen location of the watercourse crossing should:

cross watercourses at right angles;

select crossing points which:

- are immediately downstream of straight and stable watercourse sections;
- have easy high bank access;
- do not require deep box cuts;
- require minimum alteration or disturbance to the high bank;
- have stable beds.
Temporary crossings

Temporary crossings are permitted to allow equipment involved with the construction of the watercourse crossing to be moved to the other side. They should be constructed as follows:

the width of temporary crossings is limited to 4 metres;

the temporary crossing is to be made on the final crossing alignment, so as to reduce disturbance to watercourse banks and buffer vegetation (Figure 6-7).

Permanent crossings

Permanent crossings must be of a size to allow wet season flood flows to pass without damage to the crossing or its foundations. (Government authorities may be able to provide information on flood levels, as will local inhabitants.)

The height from the stream bed to the bottom of the bridge deck must be at least equal to the height of the high bank.

The width of the crossing must be at least equal to 80% of the width of the watercourse measured from high bank to high bank.

All water crossings must be single lane.


Excavators should be used where possible for the construction of all watercourse crossings. Manual labour should also be considered as appropriate in specified circumstances.

All earthworks should be carried out so as to prevent soil entering the watercourse. No soil is to be used or placed past the high bank without first having erected and secured a suitable barrier.

Road construction within the buffer area should be by end-haul.

All spoil should be removed to outside the buffer areas or placed in road fills where possible.

Watercourse buffer vegetation should be retained to the edge of the crossing.


Bridge and culvert foundations are to be located on stable materials.

The foundations are to be excavated to a solid base and not formed by pushed material.


No machinery will operate in the watercourse during construction.


Approaches must have a straight and level alignment for a minimum of 10 metres on either side.

Decks can be constructed of durable sawn timber, or other non-erosive material (e.g., clean rock fill). Soil fill or soil covering is not permitted unless the timber deck is completely covered with material such as geotextile and has protection beams on both sides.

All parts of the bridge must be well anchored to prevent their washing away.

The stream banks adjacent to the bridge, on both the top and bottom sides, must be stabilised using wings of durable logs, stone pitch or other equivalent construction (Figure 6-8 and Figure 6-9).

Figure 6-7: Temporary Bridge

Figure 6-8: Timber Bridge

Figure 6-9: Soil Covered Timber Bridge

Culverts and pipes

May have earth fill, but must have stable abutments constructed to the level of the running surface to prevent spoil entering watercourse.

Scour pads (structure to minimise erosion) should be provided at culvert exits. They should be used if higher energy water flow is likely (Figure 6-10).

All culverts should have a cut-off wall to prevent erosion under the pipe.

The head and outlet walls should be stabilised with log or stone pitched walls.

Culvert gradients should be 1-3%.

Use of log culverts is discouraged and should only be used for culverts on temporary roads.

If log culverts are used, geotextile or another retaining mechanism should be used to retain backfill.

Figure 6-10: Culvert Construction

Fords/low-level crossings

Low level crossings should:

minimise earth moving and impact on the stream bed;

should be built level to allow water to flow;

should have upstream debris deflectors above the crossing to deflect debris which might cause scouring above the crossing;

enable deposited gravel to be removed and used for roading material;

provide protection against scouring below the crossing unless the bed is solid gravel or stone.

Silt traps

Silt traps are to be provided at the four corners of bridges and culverts.

Silt traps should be cleaned regularly.

6.3 Log Pond and Wharf


To minimise the area used for processing and shipping of logs.

To avoid adverse impacts on the marine environment.

To store logs in a manner that minimises damage and loss.

To prevent log off-casts from entering watercourses or the sea.


A log pond and wharf loading ramp plan, showing the location and construction specifications should be submitted to the relevant authority prior to construction.

Gently sloping areas (up to 6%) are preferred to promote drainage.

Constructing log ponds by filling reclamation areas below low-water mark will only be considered where:

- there is no alternative;
- construction and operation will not damage the adjacent marine environment;
- and drainage water is directed away from the sea.
Locate to provide the best and most direct access for log ship barges. Deep-water ports are preferred to reduce the cost and disturbance associated with barging operations.

Retain a 50-metre buffer area between the log pond and the shoreline (or mangrove vegetation) or a watercourse.

Clearing of shoreline or river frontage vegetation (including mangroves) should be limited to that necessary to construct the wharf and associated log storage area. A maximum frontage of 100 metres is desirable.

Timing of construction

Construct the log pond and wharf in dry weather.

Excavators should be used where possible for construction to minimise disturbance to surrounding environment.



Log pond areas should be well drained. Spoon drains (3-4 metres wide and 30 cm deep), constructed at a maximum interval of 40 metres will channel runoff to vegetated outlets. The maximum slope of spoon drains should be 1-3%.

The major crossing points of drains should be gravelled to a depth of 30 cm. The gravel should not restrict the flow of water along drains. Where gravel is not available, crossing points should be corded so that the top of the cording is level with the base of the drain.

Drains should not directly enter water bodies. Water must be filtered by a designated filter strip.

Log and waste storage areas between the drains should be elevated with a crossfall of 4-6% and should be at least 1 m above high tide level.

Fuel storage areas should be bunded and located at least 50 m from the high tide mark.


Construct using clean gravel fill only. Soil material should not be used.

The loading face of the wharf should be a wall-type construction with a top log. Walls may be constructed of round timbers, rock or other material able to prevent slumping of wharf fill into the sea. All timbers should be secured to prevent their falling into the sea. Only durable timber species should be used.


Drains should be kept open at all times.

Silt traps should be cleaned regularly.

Log storage areas and the surface of the wharf should be kept elevated by applying gravel or coral as required.

Existing log ponds and wharves

Earthworks and other rehabilitation are required to bring existing facilities to these standards.

Decommissioning of log ponds and wharves

The drainage system should prevent stormwater runoff from the site entering watercourses or the ocean without first passing through a filter strip. Water bars may be required.

All stream beds should be restored to allow unimpeded flow of water.

All waste, waste oil and fuel must be removed from the site.

6.3.1 Barging/Beach Loading


An area should be selected that will:

minimise damage to the shoreline;

minimise the requirement for machinery to enter the water (machinery should only enter the water with the approval of the Forest Authority Officer).


Adequate drainage (as detailed for log ponds) must be installed.

If damage from vehicles might occur on the waterline strip, cording should be installed as a protective measure.


The drainage system should prevent stormwater runoff from the site entering watercourses or the ocean without first passing through a filter strip. Water bars may be required.

All stream beds should be restored to allow unimpeded flow of water.

All refuse, waste oil and fuel must be removed from the site.

Cording should be removed from the waterfront.

6.4 Quarries


To provide appropriate material for road/landing/log pond surfacing for harvesting operations.

To minimise disturbance to forest and watercourses.

6.4.1 Bedrock or Gravel from Dryland Deposits

Quarries should be located within production forest areas where possible.

Extraction of gravel and rock materials from road cutting areas during the formation of the road is preferred to the development of large quarries.

Proposed quarries within areas excluded from harvesting require the inspection and approval of the responsible Forest Authority Officer.

River gravel

Obtain the approval of authorities other than the Forest Authority if this is a legal requirement.

River gravel will only be used where quarry rock material is not available.

River gravel or rock will only be taken from deposited fans in wide rivers.

Gravel or rock is not to be excavated from incised streams.

Reef material from marine areas

Limited extraction of dead reef material will be considered only if:

the impacts of dead reef coral mining are less than those associated with obtaining material from other sources;

it is taken from areas dedicated to wharf construction or ramps;

no other gravel material is available.

If the reef area is within a declared fish breeding ground or habitat area, the approval of other authorities should be obtained where this is a legal requirement.

6.4.2 Quarry Management

All commercial trees should be harvested on the proposed quarry area.

Drains should be constructed around the uphill side of the quarry to prevent runoff entering the area. The drains are to direct all runoff away from the quarry and are to direct water to vegetated areas where possible.

The base of the quarry is to be drained at all times. Drains must not directly enter watercourses.

Overburden including topsoil and organic debris should be stockpiled for spreading in the quarry surface when operations are completed. Runoff should not be allowed to pond in the stockpiled area.

The face of the quarry should be maintained in a stable condition at all times.

Blasting operations should be carried out by certified personnel only. Strict public safety measures should be followed at all times with signs and guards posted at safe distances to prevent entry to the danger zone during blasting operations.

6.4.3 Quarry Rehabilitation

Rehabilitation should occur progressively as quarry areas are no longer used.

Removed overburden should be replaced followed by topsoil and organic matter.

The site should be replanted/resown with trees, shrubs or a cereal crop.

[2] Slope conversion table is provided in Appendix II.

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