The potential of sand dams road crossings
In many African dryland regions, culverts are traditionally built under low-volume rural roads (LVRRs). Rainfall in dryland regions is characterised by short intense rainfall that quickly flows into ephemeral rivers carrying large sediment loads. Such rivers typically flow for just a few days or even hours each year. Culverts or vented fords allow water to flow underneath the road. Often their capacity is inadequate to accommodate the peak flows and over time upstream sedimentation reduces this capacity further. As a result, culverts are vulnerable to being washed away and often require regular expensive repair. Sand dams that incorporate a river ford crossing are a viable alternative to culverts that offer significant additional benefits. Correctly designed sand dams manage flood flows and in many circumstances are a robust and cost-effective alternative to culverts. Amongst the additional benefits, sand dams recharge the aquifer, reduce downstream flood risks and provide a reliable, year round water supply in water scarce environments. This paper documents a case study from Kenya where a sand dam is used as such a road crossing as well as acting as the source for a water pipeline and kiosks. The paper describes the principles for siting, design and construction of sand dam road crossings and defines under what circumstances this approach is appropriate. It discusses the barriers and enablers to wider adoption and proposes pathways to scale-up the approach.
Neal, I. The potential of sand dams road crossings. (2012) 25 pp.