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decreasing to 0.2 m at the tips. The technique can be used for trees and grass but it
is best suited for row crops where manual work is the mode of cultivation. The stan-
dard design method is used to size the required catchment area (Oweis et al. 2001 ).
4.2.5 Contour Stone Bunds
These are made of stones laid on the contour on up to 2 % slope in areas with
200–750 mm rainfall. They are suitable on stoney land, and are used to slow down
runoff and filter out the soil, and to increase infiltration of runoff water. Contour
stone bunds can be used without spillways and have low construction and mainte-
nance requirements. This technique is well suited to small-scale application on
farmer’s fields and, given an adequate supply of stones, can be implemented quickly
and cheaply over large areas.
The spacing between stone bunds is normally 15–30 m but should be decreased
as the slope increases. The minimum height is 25 cm with a base width of 35–40 cm
set into a 5–10 cm deep trench which acts as a key. On slopes less than 1 %, bunds
are spaced at 20 m and on 1–2 %, 15 m. Bunds are made with a good mix of large
and small stones to ensure that the runoff is allowed to pass through slowly (Fig. 7 ).
The small stones are normally placed upstream and the large stones downstream
(Hai 1998 ).
Fig. 7 Contour stone bunds in Kenya (left) and Syria (right) (Source: http://www.infonet-
biovision.org/EnvironmentalHealth/introduction-soil-conservation-measures; Akhtar Ali)
A. Yazar and A. Ali