THE NATURAL ENVIRONMENT

Environment: sustainability conflict Sustainability of rural roads depends on harmonious relationship with the environment Rural road design is largely water management: main agent of destruction is flowing and standing water Sustainability depends on durability and maintenance Rural roads very vulnerable: traffic cannot justify big investments so durability must be sacrificed Technical standards must be modest to keep maintenance costs down

Environment: water damage (1) Roads are most vulnerable when slopes and curves make water speed up or change direction And when they are low-lying or with many water crossings In tropical countries gravel is poor so the surface, vital to keep the foundation dry, is easily washed away

Environment: water damage (2) Evacuation of water in the wrong places can cause erosion and crop damage: carefully study what is at the receiving end Borrow pits for gravel form loci for erosion and stagnant water: contractor must restore them

Principles for minimal mutual interference Raise service quality of roads only to that needed by traffic Ensure that they are maintainable at that level Concentrate on drainage, especially structures Use labour-based methods to minimise footprint of construction works Use durable materials on steep slopes Think again about using gravel especilally if it is distant or poor quality Do not neglect or under-finance preventive maintenance

Connected modules Road surfaces Labour-based works

References Environmental protection.doc Environmental impact of road projects.pdf