Soil and Water Bioengineering (SWBE) in Africa: First experience and lessons-learned in Burundi

Abstract

Burundi's landscapes are threatened by land degradation and erosion, like many other countries in Central Africa. Environmentally, socially, and economically sustainable technologies should be investigated to address the issue, and Soil and Water Bioengineering (SWBE) represents a suitable solution. This study describes the first-ever application of SWBE in the country, realized within the World Bank's Burundi Landscape Restoration and Resilience Project (PRRPB). An experimental installation of SWBE was implemented in the hilly Isare municipality (Colline) using the training sites method. The overall feasibility of the installation was evaluated through an analysis of the growth of the plants used – a botanic analysis - a transferability analysis and a cost analysis. The botanic monitoring highlighted that a relatively good survival rate was achieved at the site of the experimentation. The transferability analysis results showed minor constraints (mainly know-how on SWBE techniques and the availability of materials, qualified labor, and equipment and mechanical instruments) but no major ones. On the other hand, the presence of high botanical knowledge, jointly with the local biodiversity, and the economic advantages of SWBE, represent decisive factors that can guarantee successful transferability. In terms of costs of a sample SWBE technology (double crib wall), our results show a reduction of 42 % and 72 % in terms of Purchasing Power Parity $ (PPP$) for mechanical and manual excavation respectively, with reference to the cost of the same work in an EU country (Italy). In addition to this, such technology is much cheaper than a gabion wall (−25 % if the crib wall is installed with mechanical excavation; −105 % if with manual excavation) and a concrete wall (−326 % with mechanical excavation; −598 % with manual excavation). The results of this paper show that SWBE is potentially transferable to Burundi, allowing the solution of some of the land degradation problems in the country, specifically targeting small- to medium-sized landslides, and also to countries with similar landscapes and social settings. More experimental installations and more research on the barriers should be realized. The proposed approach can be replicated in any central African country endangered by erosion and landslides.