Q: My
crew is in the middle of thinning a 15 year old pine plantation. In the middle of the tract, leading down to
an intermittent stream is an old legacy road that has washed out over time. It is very apparent that the when all the
timber was harvested over 15 years ago that no BMPs were used. As this gully approaches the stream it gets
deeper and deeper. Where the gully meets
the stream it is deep enough to swallow a pickup! For the most part, the gully hasn’t eroded
any more in quite some time. There is
little to no evidence of recent soil movement, and there is a pretty heavy
layer of pine straw and other litter on top of the soil. We have kept all our equipment out of the
gully and haven’t cut any trees on the edge of the gully in order to keep things
from washing out anymore than they already are.
What is our next move here? How
should we treat this highly eroded legacy road in future management
operations?
A:
Excellent question, and one that addresses an issue that I am sure other folks are
experiencing out there. First and
foremost, good job staying out of the gully and not harvesting the trees along
the edge. Even though the gully started
out as a poorly placed road, it is now acting as an ephemeral drain and should
be treated as such.
The
best way to keep this gully from eroding further is to keep equipment out
entirely and to maintain a buffer of trees around the edge and above the head
of the gully. Now you may remember that
Texas Forestry BMP guidelines do not require an SMZ on ephemeral drains, but
depending on the situation, some protection is needed. This is certainly a situation where some
protection is needed. The amount of
protection, the width of the buffer, will depend on the soil type and
topography of the site, based on your professional judgment.
The
buffer will accomplish several goals in the name of erosion prevention and
protecting water quality. The first goal
is interception. The canopy of the trees
comprising the buffer will intercept rainfall and reduce the resulting soil
movement from raindrop impact. The
second is root structure. The roots of
these trees will hold the soil in place, reducing the chance of the gully
getting wider. Since you are in the
process of harvesting timber on site, the amount of water traveling to the
gully is going to increase. This surplus
of water is a result of the harvested trees not being there to use it
anymore. The trees making up the buffer
will intercept the bulk of this water, preventing further erosion.
Maintaining
a buffer also limits equipment intrusion.
Remember, since water is naturally draining towards the gully and in
more abundance with less timber around to utilize it, the area around the gully
is going to be much more prone to rutting.
Even in dry conditions it is important to minimize equipment operations
immediately adjacent to the gully as this can cause soil disturbance that will
eventually lead to further erosion issues.
While
it may seem like a good idea to place hay bales, slash, or silt fences in the
gully, this should be avoided. In a case
such as this, where everything seems to have stabilized relatively well,
putting something in the gully would likely cause further erosion on the side banks
causing the gully to widen. Placing hay
bales or silt fences in the gully would not only enhance erosion, but also
costs time and money. Time and money
that you could be devoting to other aspects of your operation, such as
installing BMPs elsewhere!
*This article was published in the September 2013 edition of the Texas Logger