How to use a topographic map for timber harvest
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
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.
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.
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.
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.
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.
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.