Fencing Work - Afforestation, Reforestation and Forest Restoration in Arid and Semi-arid Tropics - page 78

Outlets for drainage at the base of the wall should be left at appropriate places.
Liberal space should be left, so that no damage is caused even during unexpectedly
heavy rains. Size of each individual gap should be small since small animals may
find these holes convenient for entering into the plantation.
Correct section of a wall can be ensured by measuring its height and top width us-
ing a tape but its base width cannot be measured easily after construction. Therefore,
the marking of lines on ground before starting the construction of the wall is impor-
tant. While measuring height, allowance should be made for the sloping ground. The
outside height should not be less than the prescribed height since it is this side that
acts as a barrier to animals.
For plantations that would need to be fenced for longer than 5 years, it is better
to lay a layer of binding material on top of the wall. This could be done by laying
a coping in soil-cement mortar with two strands of barbed wire running through the
length. Mud mortar, lime-sand mortar, or bituminous mortar may also be used if
deemed cheaper or convenient. This will effectively prevent falling-apart of stones
from the top, and give the wall a stable and long life. Afforestation works involving
natural regeneration in arid climate may require more than a quarter of a century
to establish, and in such cases this is a desirable technique for ensuring prolonged
fence life.
A dry stone wall will require constant maintenance. A small section of the wall that
is damaged and not repaired for a long time can lead to destruction of the plantation.
Constant vigil must be kept over damaged sections of the wall and the same must be
rebuilt immediately. A wall may fall due to rain and storm, animal or human activity,
and soil movements.

4.2 Ditch-Cum-Bund Fence

The success of a ditch-cum-bund fence (Fig. 4.2 ) will depend upon its suitability
at the site. Sites with excessive slopes—more than 2 %—or with light soils are not
suitable for this type of fence. On a sloping ground, rainwater will run in the ditch
and make it into a gully, destroying its section and alignment. In sandy soils, neither
the ditch nor the bund will be stable. Sites with inadequate soil depth or varying
depths should not be fenced with this method since the required depth will not be
excavated and the purpose of protection will not be served.
Alignment of a ditch-cum-bund fence should be first marked on ground with two
parallel lines at a spacing equal to the top width of the fence. Stretches, however short,
that run across a stream draining the area should be excluded from such alignment.
These stretches may be fenced with barbed wire. Similarly, if sloping stretches are
suddenly encountered, these too should be omitted in favour of the barbed wire fence.
Soil should be excavated with the help of proper tools and formed into a bund
on the inside of the plantation. Side slopes of the bund should be neither too steep
nor too flat. Steep slopes will collapse and the soil will spread out whereas too flat a
bund will not be an effective barrier to animals. Soil texture will decide the optimum