Fanya juu bund is similar to soil bund in many aspects. However, fanya juu bund is constructed by throwing the soil uphill to form an upside embankment and can easily develop to bench terraces as compared to level bunds.
Figure 55. Cross-section of trapezoidal fanya juu.
Fanya juu construction requires higher labour than soil bunds because of uplifting of soil material. It is suitable for slopes between 15 and 30 %, soils deeper than 1 meter and medium rainfall areas. Fanya juu can be either a rectangular or trapezoidal in cross-section.
It is easy for farmers to make rectangular one but trapezoidal fanya juu is more stable.
Furthermore, fixed values for dimension of fanya juu are given based on the following schematic representation of a trapezoidal cross-section (Figure 55):
A 20-25 cm Berm is required between the embankment and the channel in order to prevent sliding of the soil into the channel. However, a fanya juu bund portrayed in Figure 56 is without a Berm. In this case there is a high risk for the embankment to slide into the channel. Moreover, the excavated soil should be placed in proper space, levelled and compacted when it is moist by people walking on it or using locally available material.
Figure 56. Fanya juu bund without Berm, FFA Kitui District, Kenya.
A good grass cover should be established on the embankment, and a strip of grass should be planted along the upper edge to prevent the inflow of sediment and reduce land lost too crop production due to the structure. The plants can be used for different purposes such as fodder, food, soil fertility enhancing (composting) and mulching. Some farmers plant bananas in the channel beds of Fanya juu bund. This is practiced for two reasons. Firstly, to economise space reduced for crop production due to construction of this structure. Secondly, to effectively use moisture stored in the channel.
Fanya juu without Berm
Work norm elements: Same as for soil bunds except that a Berm in this case should be slightly greater than that of soil bund.
Work Norm: 200 person days per kilometre.