1. THE NATURAL ENVIRONMENT

2. 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

3. 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

4. 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

5. 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

6. Connected modules
Road surfaces
Labour-based works

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