Page 180 - RoadCem Manual - PCT BV

6.6 Erosion 6.6.1 Introduction
Any disruption to the natural flow of water carries a risk of erosion that may lead to environmental, degradation, silting, damage to roads, damage to buildings and services, destruction of farming land and loss of fertile soil.
Thus, there is a responsibility to ensure that the construction of the drainage system for a road receives the same attention to good practice as the construction of other roads. Indeed, avoidance of erosion can be more critical in the case of roads because of the greater challenges faced in maintaining the drainage system in remote areas where these roads are often located.
6.6.2 Scour Checks
There are many examples of inexpensive and effective methods that are used to protect drainage channels and side drains by the use of scour checks that are easily constructed by labour-based methods. The scour checks can be made of wooden sticks, rocks, concrete or in situ material stabilized with RoadCem depending on the most economical source of materials. The frequency of scour checks needs to be properly adjusted according to slope gradient in order to prevent erosion between the checks causing damage to the system. The following table can be used as a guide:
Table 6.1 Gradient of the ditch
Gradient of the ditch
Scour check spacing
4% or less 5 %
8 %
10 %
6.6.3 Erosion of Culverts
Not required 20 m
10 m 5 m
Short culverts requiring high headwalls and wing walls are built to avoid erosion around both inlets and outlets, especially along the wing walls. Constructing culverts that are sufficiently long to reach the toe of the embankment will minimise necessary protection measures, future maintenance and the risk of damage to the embankment around the openings. It is necessary to carefully assess the additional cost of lengthening culverts against these benefits, especially in the case of roads that are often located in remote areas where regular maintenance is a challenge.
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