Combination of Traditional Knowledge and Industrial Techniques to Successfully Control Erosion in a Mountainous Environment in Guinea, West Africa

This paper will review of combination of traditional and modern techniques that are used to manage erosion and sediment control at a developing mine. The mine has the combined challenges, high gradient, high rainfall, and large areas of disturbance. The ESC practices presented in the session are critical for long-term protection of water quality and conservation of soils. They also set the foundations for successful site rehabilitation after disturbance.

Full Abstract: Combination of traditional knowledge and industrial techniques to successfully control erosion in a mountainous environment
Effective erosion control is essential when on a mountain peaking at more than 1200 m above sea level, in an ecosystem rich in valuable biodiversity, with an average annual rainfall of more than 2000 mm per year, and being surrounded by waterways and riparian communities that are deeply dependent on waterways for socio-economic activities. Minimizing erosion and protecting water quality are some of the challenges for the Simandou project (Guinea). A combination of native species, civil engineering techniques, local traditional knowledge, and best industrial practices are used to achieve this. To be able to control erosion and sedimentation in this region, the Simandou rehabilitation team carries out the following activities:
Methodology
1 – Development of stone settling and sedimentation basins: We maximize the use of stones in drains and the construction of rock walls along waterways. This traps sediment and reduces the speed of water runoff. In certain critical locations, we combine this technique with the construction of gabions combined with a geotextile membrane to better control water and enable settlement of suspended sediments.
2 – Traditional Knowledge: Africans have controlled erosion using the following techniques:
The construction of mounds of 60 cm at the base and 35 cm in height to reduce the speed of water runoff and promote infiltration. These are used to create terraces, by referring to the contour curves of the land. The walls are partitioned by secondary walls and together form compartments. In each compartment the earth is flattened and rainwater runs off is slowed. Stone lines, bunds or low walls, basins, ridges as well as natural Secko woven into mats are among other traditional erosion control practices used in Africa.
3 - Spreading a layer of arable soil: Land rich in plant matter is carefully moved to a depth of 10cm to 20cm during the work. It is then respread on bare surfaces to allow vegetation to reestablish and reduce the impact of sediment on watercourses during rains. In some applications soil is allowed to germinate from the natural seedbank in the soil, or it is hydroseeded to provide quick stabilization.
4 - Hydroseeding: A mixture of water, mulch, Hydropam, organic fertilizers and seeds of different grass species (primarily Pennisetum, Melinis) are applied on the embankments to encourage the return of local vegetation in three weeks. The seeds used in these operations are harvested in the Pic de Fon and Ouleba regions, as well as in surrounding villages, thanks to the support of local communities, which also provides economic benefit to local communities and businesses that participate in the seed collection.
5 – Planting Vetiver: Vetiver is a herbaceous plant that is particularly useful for combating erosion, thanks to its dense root system, which extends up to 3 to 4 meters into the soil. This plant has existed in Simandou for more than 15 years, stabilizes the soil within a radius of 4 m, allowing vegetation to develop quickly. This is why vetiver is planted on steep embankments to stabilise slopes.