Rebuilding Haiti must start from the ground up, with agricultural education
I am in Haiti for the fifth time, and the third time in the past 13 months. I’m still appalled by the state of the dirt roads out in the countryside. It really isn’t all the difficult to design, build, and maintain a dirt road even with labor based methods. So here, finally, is my road rant, drafted between 2 and 3 am night before last when I woke up and couldn’t get back to sleep. A thought is a terrible thing to mind!
This road needs erosion protection badly as most in mountainous Haiti
The construction and maintenance of dirt roads is based on one simple fact and one simple rule. The fact is “Water runs downhill”. The rule is “Get the water off the road”. All the rest is details.
In order to minimize the damage that water does to a dirt road we need to get the water off the road. In order to do this we either 1) crown the road – build up the center and make the water drain to ditches on both edges, or we 2) pitch the road – slope the road surface toward one side so all water from the road runs to one ditch. Unless a pitched road is along a ridge, an upper ditch will be required to handle water coming from land above the road. A crowned road is generally preferred.
If we allow water to run down the length of the road itself, when it rains, the road will become a riverbed. A riverbed has a meandering course with single or multiple channels. This makes for a bad road with a very irregular surface. With heavy rains such a road surface can experience severe erosion and further degradation.
Ditches must be constructed to contain the flow of water off the road and from adjacent land during rains. Since water runs downhill all water from land uphill from the road will flow toward the road. This water must be kept in ditches and not allowed to run down the road. Where there are large amounts of water in ditches, the ditches will need to either 1) be reinforced with concrete or 2) lead to drains to get the water quickly
away from the road. The choice between these will depend on the surrounding terrain and the willingness of adjacent landowners to allow drains. In general, drains are preferred as they are generally the less expensive. Ditches and drains must be wide enough and deep enough to handle the flow without excessive erosion. As the speed of flowing water increases, it moves larger objects from silt, to sand, to gravel, to larger stones. We do not want the ditches to continuously deepen themselves as this will eventually undermine the edge of the road. A broad shallow ditch is preferred. Vegetation in ditches is acceptable as long as the edge of the road is maintained so that water can flow off the road into the ditch. Vegetated ditches may require regular cleaning to remove accumulated dirt and plant debris. Dirt can be removed to adjacent land or used to build up the center of a crowned road or high edge of a pitched road. Organic debris should be removed.
Puddles in the road should be filled with stones, gravel, and dirt as soon as possible. Puddles only get worse with time. As mud (water and dirt) is splashed out the puddle only gets deeper. Low spots in the road will become puddles or mud holes. These will need to be built up with rocks and dirt to force the water to flow off the road into ditches and drains.
There are situations where it is necessary to have the water flow from one side of the road to the other in order to get it to a drain. There are several ways this can be done effectively. The first is a culvert – a large pipe that allows the water to flow under the road. A culvert need to be large enough to handle anticipated flow and strong enough to withstand the heaviest vehicles that use the road. Culverts are best made of concrete. Concrete culverts are generally stronger and require less burial depth than metal or plastic culverts. It is possible to build a concrete culvert in place using thin pipe, (or even plastic buckets or barrels with ends removed and arranged end to end) to form the inside of the culvert. Concrete with proper reinforcement is poured under around and over this core to form a culvert. Another possible water crossing is a slot, generally of durable wood or concrete. If very narrow, it can be possible to drive directly over the slot without any cover. A wider slot will require a grating or solid cover. As the slot becomes wider we end up needing what is properly called a bridge. Narrow slots are prone to clogging and must be cleaned often to maintain proper flow. Another possibility is a stone paving or concrete drain across the road. This is a wide shallow “V” that is the surface of the road which allows the water to flow across the road without causing damage. Stones must be of sufficient size to stay in place at maximum flow and need to be carefully laid.
There are situations where the road must cross existing bodies of water such as rivers or even small lakes. This will generally require a bridge. A bridge is a serious undertaking that requires proper engineering.
In some situations, the riverbed is the road, or at least the road repeatedly crosses through the river. Little can be done to improve such a road short of obvious removal and placement of stones to smooth river entries and exits.
For more detailed information on building and maintaining dirt roads see: Earth Roads: Their Construction and Maintenance, Jack Hindson, revised by John Howe and Gordon Hathway. 1983.
A practical manual for non-engineers which describes the design and construction of earth roads with a usage of up to 50 vehicles per day. Covers drainage, road planning, the actual construction, and subsequent maintenance operations.
Rural Roads Manual, 1977. Papua New Guinea’s Dept. of Public Works recognizing the importance of well-constructed and maintained roads, has published this manual in an attempt to promote self-help road construction all over PNG. Written purposely in very simple English (the national language), it is a complete guide to road design, construction and maintenance using low-cost local materials and tools, and local skills. Covers subjects such as surveying, laying out a road, drainage, building in swampy areas, maintenance and upgrading, plus information on building bridges, culverts and low-level crossings.
Road Maintenance and Regravelling (ROMAR) using Labour-Based Methods Handbook &
Workbook, 1996 Claes Axel Andersson, Andreas Beusch, and Derek Miles
Labour-Based Road Construction: A State-of-the-Art Review
Edited by Paul Larcher, 1998
Roads and Resources:Appropriate Technology in Road Construction in Developing Countries,
G. Edmunds and J. Howe, 1980
Understanding Low-Cost Road Building, David K. Blythe
Outlines planning, equipment, and maintenance requirements for building simple roads.