Improved paths and tracks: Part 3
Practical Action
Combating erosion
Erosion becomes more of a risk to paths and tracks as the terrain steepens, because the
erosive power of water increases with the increased speed of flow. As paths and tracks are not
covered by a protective layer of vegetation, such as grass, they are particularly prone to
erosion. They can even become
waterways themselves, resulting
in an accelerated cycle of gulley
Rise
0.15 – 0.25m
5 - 7%
Wood or
bamboo poles
about 0.15m
diameter
formation, rapidly destroying the
surface of the path. To reduce
the risk of erosion on paths and
tracks it is necessary both to
Wooden
stakes 0.5m
long
control surface run-off and to
avoid excessive concentrations
of water flowing over their
surface. One common and
Tread
0.5m or 1m
inexpensive method of diverting
surface water off paths is to
construct water bars across the
path. Similar methods can be
Figure 6: Construction detail of timber pole or bamboo
steps
used on tracks, but water bars
are less convenient for the
passage of wheeled traffic. The
principle of the water bar is that
it intercepts surface water
flowing along the path and diverts it off the path to one side. Water bars can be constructed in
stone or timber. The desirable angle of the water bar to the path varies with the steepness or
longitudinal gradient of the path: the steeper the path, the greater the angle necessary. A
typical timber pole water bar is illustrated in Figure 7.
3 logs
1 x 200m diameter
2 x 100 – 120mm diameter
Edge of path
25 - 45º
(see table)
Stakes
Edge of path
Water
Figure 7. A timber pole water bar
Gradient
of path %
5
10
>15
Angle of
Water bar
25º
35º
45º
4