Gully stabilisation in Mafumba after intervention
UNEP
Gully and soil erosion control
Reducing gully erosion was important to reduce siltation of springs and streams in low lying areas and destruction of infrastructure. In order to treat and arrest the formation of gullies, the project implemented a bioengineering technique using vetiver, a grass known for its deep roots that can effectively control soil erosion. In this method, soil-filled bags are compacted in gullies to arrest progression of gullies. Vetiver are planted in the top soil-filled bags (filled with fertile soil). The bags will normally deteriorate and breakdown under the sun, but the roots of vetiver keep the soil in place.
River banks were also stabilised with vetiver grass after removing uneven projections and smoothing the slope. Vetiver nurseries were set up to supply the two working areas (near the water treatment plant and near Kinshasa).
A local charity near Kinshasa, where limited land is available for community projects, provided space for a vetiver nursery.
The use of vetiver for gully and soil erosion control was also very successful, because local residents immediately perceived the protection value provided by the vetiver, especially when sites are located near their homes, schools or public roads. Prior to the project, communities in the basin did not know about the effectiveness of vetiver grass as an erosion control measure. Now neighbouring communities have shown great interest in replicating the bioengineering methodology.