Semi-circular bunds are usually made of earth or stone and have commonly a diameter of 2-8 m (up to 12 m). The bund tips are set on the contour line, facing upslope. Bunds are 30-50 cm high. They are built in a staggered sequence over a plot; that is the second line catches runoff that flows between the structures in the line above; and so on. The C:A ratio ranges between 1:1 and 3:1. In dry conditions, the bunds are bigger. In wetter conditions, more bunds of smaller radius are constructed per hectare. They are applied on slopes up to 15%, however earthen bunds are rarely used on slopes steeper than 5%, receiving more than 300 mm/y of rainfall. Larger and more widely spaced half-moons, as these bunds are called (French: demi-lunes) are mainly used for grazing land rehabilitation or fodder production. Small and closely spaced half-moons are used to grow trees and shrubs. In the Sahel they are often used to produce pearl millet. Where they are employed to grow trees for agroforestry systems with a single pit excavated at the lowest point, they effectively act as negarim. (Mekdaschi & Liniger 2013)