Forest Roads

Unit 1: Welcome to Forest Roads

Well-located, well-constructed, and properly maintained forest roads are essential to forest management activities and critical to reducing pollution impacts on forest streams. This section is a review on practices that provide necessary stream protection during road construction and management.

This section will cover:

Permanent & Temporary Roads
Road Construction
Water Control Structures and Other Water Control Devices
Road Placement

Unit 2: Permanent Roads VS Temporary Roads

Access roads are classified into several categories based on their intended use and lifespan:

Permanent Roads– Primary or secondary roads constructed to provide all- or nearly all-season access for silvicultural activities, and are maintained regularly.
- Primary Road– A high specification permanent road which is maintained regularly and serves as a main artery in a network of roads.
- Secondary Road– A permanent road that is maintained periodically, installed for transporting wood products and with a secondary use for other forest activities.
Temporary Road– A road constructed for a specific use or single operation and normally retired upon completion of the operation.

Unit 3: Permanent Roads

Permanent roads have been subdivided into two categories: Primary and Secondary.

Primary roads are the main arterial roads for a tract and are usually connected to the access points. These road systems handle a bulk of the traffic, including hauling, and are maintained on a regular basis to ensure access to the tract.

Secondary roads are less frequently used and are maintained on a less frequent basis than primary roads. However; unlike temporary roads, these road types remain open (at least part time) for vehicle traffic and for other forest uses such as landowner access or hunting access. They may have been constructed for a single job, but ultimately stay open after the job is complete.

Unit 4: Temporary Roads

Temporary roads are installed for a single job, and are meant to be closed out after the job is complete. Roads that fall into this category include but are not limited to the following:

skid trails,
harvester paths, and
one time access roads that will be closed after the job is finished.

Often temporary roads are site prepared and planted. These types of roads are not intended for further use after the operation and will not be maintained. Because of this, extra care should be taken to ensure that all necessary BMPs are installed to prevent erosion from occurring after the job is completed. Options to protect these roads include but are not limited to the following:

seeding,
constructing waterbars,
incorporating slash, and
planting trees, food plots or other ground cover.

Unit 5: Water Control Structures & Road Building Techniques

The greatest risk to water quality from forestry operations is erosion from forest roads entering a waterbody. Over 90% of the sediment deposited in streams and lakes from forestry activities comes from forest roads. Therefore, the easiest and usually least expensive way to reduce sedimentation on a forestry operation is to limit the size and number of roads needed to complete the job safely and efficiently.

Unit 6: Water Control Structures

Constructing water control structures when necessary is the next best way to ensure that erosion from the road system and resulting sedimentation into streams and lakes will be minimized. There are several types of water control structures. Each type has advantages and disadvantages. Your experience, as well as your knowledge of the tract will help you determine which structures may work best for a given situation.

Some of the site characteristics that may affect your decision of which types of structures to use may include but are not limited to the following:

soil type,
topography,
drainage patterns, and
presence of any streams.

Understanding soil type is very important in deciding which structure to install. For example, installing and maintaining waterbars on sandy soils can be very difficult. Some soil types (such as gumbo) may not even be able to support your equipment without significant damage to the soil. Carefully considering drainage patterns will help identify where water control structures will be needed to allow water to flow naturally across the tract which can go a long way in saving time and money when it comes to installing and maintaining water control structures.

Unit 7: Water Bars

Water bars are very effective structures when installed properly. They should be built 1-2 feet high, and at a 30 to 45 degree angle to the road, firebreak, or trail. The uphill end of the water bar should be tied into the bank to fully intercept any road surface runoff. They are usually most effective when used in conjunction with cross drains and/or wing ditches to allow for the water to be safely dispersed onto the undisturbed forest floor.

Water bars are much easier to construct in clay soils than sandy soils. They are also usually intended for roads which will have limited traffic (i.e. temporary or secondary roads), as they are inefficient for travel and can be very easily knocked down or breached with heavier traffic loads.

Unit 8: Road Based-Dips

If the intended traffic will be heavier trucks a rolling dip or broad-based dip may be a better alternative. Both structures act as a stretched out waterbar. The main difference between the two is in the topography in which they are used.

Broad-based dips are better for gradients of up to 12%.

Unit 9: Rolling Dips

Rolling dips should be installed on road grades of up to 15%.

Consult the 2014 Texas Forestry BMP Handbook for further information on constructing either type of structure.

One main disadvantage to these types of structures is that they are more costly and time consuming to build. If the soil type and topography warrant, you may need to use rock to protect the outfall area or to prevent rutting the road surface.

Neither water control structure should be used for cross draining springs, seeps, or intermittent or perennial stream. They are intended only to drain road surface runoff.

Unit 10: Cross Drain Culvert

Culverts can be a very effective way to get water from one drainage ditch to the other side of the road when needed. Corrugated metal or plastic pipe, wooden open box top culverts or other suitable materials may be used. Culverts can be used in any size operation where cross drainage of water is needed.

Unlike rolling dips and broad-based dips, culverts can be used to safely transmit water from seeps, springs, and intermittent and perennial streams under haul roads and skid trails. They usually last a fairly long time if they are properly maintained and inspected for obstructions.

Although culverts are very good for most operations, they do have some disadvantages. Culverts can be expensive and labor intensive to install. They are also better suited for use on permanent rather than temporary roads.

Unit 11: Wing Ditches

Wing ditches can be used to effectively divert runoff water from roadside ditches onto the forest floor. Water that is allowed to flow down steep slopes without being diverted out of the side ditch can gnaw at the roadbed, scour the ditch itself, and move soil downslope.

When installing wing ditches, try to follow the natural contour of the land. These structures should:

Open into a flat spreader
Have a slight upward “hook”
Not discharged into streams
Be spaced properly along the road

When constructing a wing ditch, try not to cut a narrow channel that has a sharp downslope angle. While this would quickly divert water away from the road, it may lead to additional erosion.

Unit 12: Other Water Control Ditches

In addition to the types of water control structures and methods listed previously, there are several other acceptable and sometimes less costly alternatives. The use of slash or brush from the site to stabilize a temporary road is often very effective and also inexpensive. Slash should be well incorporated into the ground to prevent washing from beneath. Other methods may include but are not limited to: spreading hay or seeding a road to establish vegetation if natural revegetation may take too long.

Unit 13: Road Construction

One way to control water on a road system is to ensure that the road is constructed in a way that safely and efficiently sheds water from its surface. When constructing a road, pay close attention to the topography, soil types, and drainage patterns. You can then use techniques such as crowning and ditching, outsloping, and removing trees along the road to facilitate drying as the site dictates.

The main goal is to direct the surface runoff water off the road’s surface quickly, while providing for safe and efficient vehicle travel. Water diversion structures should direct water to undisturbed forest floor and should never direct water to streams or other water bodies.

Unit 14: Road Placement

The blue line indicates a very poor choice for a road location because this location provides limited access to the entire tract. This road would more than likely be placed in a low wet area of the tract, raising concerns over ponding and rutting issues. It may also be located within the SMZ. This location would probably have significant impacts on water quality.

Unit 15: Road Placement- Yellow Line

The yellow line would also be a poor location for a road. It provides greater access to the tract, but it crosses the stream twice and also uses drainages as part of the road system. This location could certainly have significant impacts on water quality.

Unit 16: Road Placement- Green Line

A road located along the green line has good access to the tract, while also limiting its impacts on water quality on the site. Notice that there is only 1 stream crossing, it stays along the ridge tops as much as possible, goes around the head of drains, and is placed at locations where the slopes are more gentle.

Unit 17: Road Placement- Black Line

The placement of the roads highlighted in black is ideal. It has good access to the tract while also limiting its impacts on water quality on the site. Notice that there are no stream crossings due to obtaining backside access, it stays along the ridge tops as much as possible, goes around the head of drains, and is placed at locations where the slopes are more gentle. Of all the options, this is the best.

Unit 18: Forest Roads Quiz

Congratulations!

You have now completed the Forest Roads Chapter. You may now begin the Quiz for this section. To advance to the next chapter, you must score 80% or greater.

Back to