Best Management Practices: Forest
Preharvest Planning: Opportunities to Prevent Non-Point Source (NPS) Pollution
To limit water quality impacts caused by forestry, public and private
forest managers have developed and followed site-specific forest management
plans. Following properly designed preharvest plans can result in
logging activities that are both profitable and highly protective of water
quality. Such plans address the full range of forestry activities that
can cause NPS pollution. They clearly identify the area to be harvested;
locate special areas of protection, such as wetlands and streamside vegetation;
plan for the proper timing of forestry activities; describe management
measures for road layout, design, construction, and maintenance, as well
as for harvesting methods and forest regeneration.
Factors Considered in the Preharvest Plan
Surveying the Site. Pre-activity surveys can help identify areas
that might need special protection or management during forestry operations.
Sensitive landscapes usually have steep slopes, a greater potential for
landslides, sensitive rock formations, high precipitation levels, snowpack,
or special ecological functions such as those provided by streamside vegetation.
Forestry activities occurring in these areas have a high potential of affecting
water quality.
Timing. Because most forestry activities disturb soil and contribute
to erosion and runoff, timing operations carefully can significantly reduce
their impact on water quality and aquatic life. Rainy seasons and fish
migration and spawning seasons, for example, should be avoided when conducting
forestry activities.
Establishing Streamside Management Areas (SMAs). Plans often
restrict forestry activities in vegetated areas near streams (also known
as buffer strips or riparian zones), thereby establishing special SMAs.
The vegetation in an SMA is highly beneficial to water quality and aquatic
habitat. Vegetation in the SMA stabilizes moderates water temperature by
shading surface water and provides habitat for aquatic life. For example,
large trees provide shade while alive and provide aquatic habitat after
they die and fall into the stream as large woody debris.
Managing Road Construction, Layout, Use, and Maintenance. Good
road location and design can greatly reduce the transport of sediment to
water bodies. Whenever possible, road systems should be designed to minimize
road length, road width, and the number of places where water bodies are
crossed. Roads should also follow the natural contours of the land and
be located away from steep gradients, landslide prone areas, and areas
with poor drainage. Proper road maintenance and closure of unneeded roads
can help reduce NPS impacts from erosion over the long term.
Managing Timber Harvesting. Most detrimental effects of harvesting
are related to the access and movement of vehicles and machinery, and the
dragging and loading of trees or logs. These effects include soil disturbance,
soil compaction, and direct disturbance of stream channels. Poor harvesting
and transport techniques can increase sediment production by 10 to 20 times
and disturb as much as 40 percent of the soil surface. In contrast, careful
logging disturbs as little as 8 percent of the soil surface. Careful selection
of equipment and methods for transporting logs from the harvest area to
areas where logs are gathered can significantly reduce the amount of soil
disturbed and delivered to water bodies. Stream channels should be protected
from logging debris at all times during harvesting operations.
Managing Replanting. Forests can be regenerated from either seed
or seedlings. Seeding usually requires that the soil surface be prepared
before planting. Seedlings can be directly planted with machines after
minimal soil preparation. In either case, the use of heavy machinery can
result in significant soil disturbance if not performed carefully.
From
EPA
Pointer
No. 8
EPA841-F-96-004H
