Glossary - Afforestation, Reforestation and Forest Restoration in Arid and Semi-arid Tropics - page 253

most cases conservation forestry provides enough secondary benefits to the com-
munity to justify it as an economic activity even while not taking into account the
intangible benefits of conservation.

Container bed ⇒ Bed

Containerised plants Plants raised or potted in containers, in contrast to the bare-
root plants.

Contingency charges In a project, or estimate of a work, provision kept for unfore-
seen, or uncertain or contingent items of expenditure that cannot be listed in advance.
Often this kind of charge is not more than 5 % of the estimated total cost of a work.

Contour bund An embankment of earth constructed on contour to check flow of
water. A bund has a definite section, usually trapezoidal in shape, with sectional area
ranging from 0.50 to 2.50 m 2 .

Contour dyke A wall of short height made of dry-stone masonry running on a
contour line, and designed to retain soil being washed down with runoff on rocky
steep slopes. Often the wall is provided with coping in mud mortar to make it stable
over a longer period. Soil is filled on the upstream side of dyke to make it into a
terrace with a little reverse slope. This then is called a contour dyke-cum-terrace.
Contour dyke-cum-terrace ⇒ Contour dyke

Contour furrows Furrows made by ploughing ground on contour line. These can
also be made by manually excavating ground where a tractor cannot be used or is not
available. The contour furrows are meant to harvest surface runoff and to conserve
soil. These are used in areas with a ground slope less than 1 %, and where grass or
legumes are to be sown on a large scale, such as in silvipastoral plantations.

Contour line An imaginary or real line marked on ground running through points
with the same elevation. The slope along a contour line is always zero, and slope in a
direction perpendicular to the contour line is the maximum slope of the ground. All
soil and water conservation structures must be aligned on the contour.

Contour terrace ⇒ Bench terrace

Contour trench A trench of square or rectangular cross section excavated on a
contour line for the purpose of arresting flow of water in sloping ground. Its section
depends upon depth of soil and its excavatability. Usually sectional area ranges
from 0.10 to 0.30 m 2 . Spacing between two contour lines for c-trench is so designed
that the runoff resulting from the average expected precipitation can be effectively
intercepted.

Contour V-ditch Same as contour trench, except that the geometric shape of the
section excavated is flattened on the upstream side so that it provides greater surface
for percolation of water into the ground. It should be preferred to a contour trench
where ground slope is less than 1 %. Space between two contours for V-ditch is kept
from 20 to 50 m depending upon permeability of the soil and slope of the ground.