Silviculture and Cinegetics Review - Societatea Progresul Silvic

FORESTRY BELTS SILVICULTURE AND CINEGETIC REVIEW XVII/30/2012
Principles of creating the communication ways protection forest belts
and their implementation in the current design practice
1. Introduction
Ilie Muşat
The communication ways protection forest belts (we
will call them hereinafter snow protection forest belts)
form a separate chapter in the domain of protection
forest belts.
Their main characteristic is the great economic role
which they play, they have to ensure unimpeded
movement of vehicles, whether road or rail, heavy
snow falls involving enormous expenditures for
removing their consequences, consequences that may
include even loss of lives. Hence the clear
implications that lies in the appropriate design of this
type of belts.
In terms of weather, in a paper of 2006 I stated that
heavy snow falls the most powerful and most
frequently occur in the case of the combination of
height the so called blizzards, when the snow
transport takes place during its falling, with blizzards
when it surface does not snows but, at wind speeds
exceeding 4 m/s (the phenomenon reaches maximum
intensity at speeds of 6-7 m/s), the already fallen snow
is engaged and moved to the surface. Note that the
involvement of the already fallen snow can occur even
in clear but dry weather. Accumulation takes place in
compact layers with high specific gravity. Once an
obstacle is met deposit as drifts occurs. Their shape is
characterized by asymmetry of slopes, more steep in
the lee of the obstacle, the slope being more
pronounced the more the obstacle, in our case the
forest belt, will be wider.
Between the width of the forest belt and the amount of
snow retained there is, as expected, a close
connection. Thus, if at a forest belt width of 30 m
there is a deposit of up to 50 m 3 of snow at linear
meter length, at a blizzard of the same strength, a
forest belt of 70 m wide holds over 300 m 3 /m.
Therefore for the design it is necessary to know, first,
the amount of snow that can accumulate on the
section of the studied passageway. For this, the
authorities of our country that manage the various
types of roads have maps of heavy snow falls on those
roads.
It should be noted, however that is not considered
justified taking into account as an element of
assessment of the width of the forest belt the
maximum possible height of drifts. Such a solution
would lead to production of large-scale snow breaks
inside of the forest belt. To reduce, perhaps avoid this
danger, it is recommended to consider the so-called
"working height" regarded as being the one that does
not lead to snow breaks within the forest belt.
Research has concluded that the most intense snow
breaks occur at a height over 3 m of the drifts at the
age of 8-10 years of the of the forest belt.
I.Z. Lupe considers necessary to be taken into account
the elements of wind, namely his strength and speed.
Another element that must necessarily be taken into
account is the transverse profile of the passageway.
From this point of view, various authors (Bodrov
V.A., Sus N.I.) distinguish three categories of
snowcapped routes:
I - cuttings with a depth of 0.4 to 8.5 m, railway
stations, land with quota 0 compared to the
passageway, but located on plateaus.
II - cuttings with depth below 0.4 m and land with
quota 0.
III - embankments with heights below 1.0 m and
highland areas with height up to 1.0 m.
Other categories of land can be considered not
snowcapped. We must draw attention that currently
there are many roads that have on the edge shrub and
even tree vegetation, which changes the profile of the
passageway and can build snow. It should also be
considered the depth of the fallen snow that is evenly
accumulated in the area and that changes the
difference in level between the passageway’s platform
and the neighboring land.
2. Width of snow protection forest belts
The lack of special research in our country (though
belts snow protection forests were planted in 1914-
1916 and then again after the World War I); require
the use of the same data of the mentioned foreign
authors. According to our theme the width of the
forest belt is determined by the ratio between the
recorded maximum transverse surface of the drifts in
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