290 Sustainable Farming
Contour Barriers
If you could make a path
across a slope that would
let you travel from one end
to the other while always
staying at the same level,
you would be following the
slope’s contour line. Barriers
built to follow contours,
such as walls, mounds, lines of grass or brush, or trenches, prevent soil from
being carried away by wind and rain. They also help slow the downhill
movement of water, spread it over the soil, and sink it into the ground. Plowing
along contours, rather than up and down the slope, slows surface runoff and
directs water toward your crops. A tool called an A-frame level can help you
find your land’s contour lines so you can build contour barriers.
How to make an A-frame level
An A-frame level is a tool that can help you find contours. Use these materials:
• 2 sturdy sticks about 2 meters long and 2 cm thick to form the legs,
and 1 stick about 1 meter long for the crossbar.
• 3 nails long enough to go through 2 sticks with a little sticking out.
• A bottle with a twist cap or cork, or a stone to use as a weight
(about ½ kilo, or 1 pound).
• A string 2 meters long with a knot tied at one end.
• A pencil or pen, a hammer or stone, a machete or saw, and a tape measure.
➊ Fasten the 2 legs together in a triangle shape with about 2 meters
between the feet. If you nail them together, leave the head of the
nail sticking out because you will use it later.
➋ Fasten the crossbar to the legs.
➌ Attach the weight (bottle or stone) to the string.
Tie the other end of the string to the head of
the nail so the weight hangs about
2 cm below the crossbar. If the bottle
is plastic, fill it with water, sand, or soil
and put on the cap or cork. The string
with a weight on the end is called a
plumb line.
A Community Guide to Environmental Health 2012