How to use a topographic map for timber harvest planning

This web article explains how loggers, landowners, and foresters can use topographic maps to plan a timber harvest.

Topographic maps are an important source of information for all forest owners. Developed and updated by the US Geological Service, they provide a graphic portrayal of hills, valleys, wooded property, and other natural features.

There are many places to buy topographic maps on-line, but you'll get better service if you simply call an outdoor outfitting store, a camping store, or your county Soil and Water Conservation District office. Support these local offices and businesses. They will help you select the right map and answer questions about how to use these useful maps. You may need to change the scale of your map (by photocopy enlargement) to match your existing property maps.

Compare the way a flat topographic map can be seen as a 3-dimensional picture:

For timber harvesting operations, consider the following ways a topographic map should be used:

Use the map to designate the location of the forest and harvesting zone. With road names, bridges, and an easy-to-read scale, topographic maps provide excellent location information.

Identify "blue lines" in the vicinity of the harvest site. Blue lines are streams with a well-defined course and year-round flow. Topographic maps use a thin blue line, interrupted by dots, to designate these streams. The term implies a stream large enough to warrant special protection if you are logging in the area. Even if a "blue line" stream is not in the harvesting zone, there is probably one close by. Make an effort to prevent sediment from your harvest operation to enter these streams.

Identify invisible streams and dry washes. By noting the way topographic lines curve, you will be able to plan better water quality protection during timber harvesting. In areas where topographic lines curve to form layered, nearly parallel "v" or "u" shapes, very small stream courses can be found. These are very sensitive to disturbance. By protecting these channels, loggers will be avoiding future erosion problems. They seldom include blue lines, but are just as important to forest health and erosion control.

Get a feel for terrain. Learn to look at brown topographic lines in three dimensions, seeing hills, valleys, and drainage areas. If the lines form a confusing jumble in your mind, ask for help from someone who is familiar with these special maps.

Locate existing roads. Topographic maps show dirt roads, old railroad grades, and even small jeep trails. The map will indicate the direction and slope of the old roads, saving field time spent hiking up or down the hills. If these are properly constructed, they can be used for logging equipment movement without harming forest soils. These existing roads can also provide options for entering the property. Field check the condition of the road and build new roads correctly rather than using erosion-prone roads.

Plan new roads to follow contours. Use the brown lines as a gauge of the steepness of the terrain. New roads should follow gentle slopes. On steeper hillsides, a series of planned switchbacks will help avoid long, straight runs. On a topographic map, count the number of contour intervals crossed by a potential forest road. The fewer contour line crossings are better.
Click each image to enlarge:

Propose log landings and roadway access. Some possible sites for log landings and fairly level terrain, close to truck access roads can be identified on topographic maps. These always need to be field checked. However, the topographic map will eliminate a lot of unnecessary labor in the field.

Identify property features on adjacent land. A neighboring property may have better access points for the timber harvest site. Consider accessing a harvest area though adjacent land to avoid steep slopes or stream crossings. If a neighbor's property is involved somehow, get written, dated permission from the neighbor allowing the logger to move their equipment accordingly. In some cases, a neighbor may be willing to sell you a permanent right-of-way.

Follow drainage patterns downstream. Some of the forest soil that may erode away from a timber harvest site could pollute important trout streams or reservoirs. Forest owners are partly responsible for ensuring logging activities do not cause environmental harm to streams and lake waters.