Roadside drainage is those structures that are made along the side of the road to drain the rainwater. Drainage helps the road to remain workable by restricting water to enter through the base or sub-base of the road.
Why do we provide roadside drainage?
- To prevent water logging beside the road.
- To prevent seepage above the road.
- To prevent roads from covering with rainwater in the rainy season.
1) Rural highway drainage
The roadside drains of highways passing through rural areas are generally open unlined of trapezoidal shape, cut to the suitable longitudinal slopes.
On plain terrain with embankments, longitudinal drains are provided both sides & in clopping terrain, it may be provided on one side only.
There is a restriction of space in this case drainage trenches of suitable depth & cross-section are dug & properly filled with layers of filter material consisting of coarse sand & gravel to form the covered drain as shown in the figure below.
2) Urban highway drainage
On urban roads because of the limitation of lane width & also due to the presence of footpaths, dividing islands & other road facilities, it is necessary to provide underground longitudinal drains.
Water drained from the pavement surface can be carried formed along the longitudinal drains. This water may be collected in catch pits at suitable intervals. The section of the side drain of the urban highway is shown below.
3) Drainage in hill roads
The efficient diversion & disposal of water flowing down the hill slope is carefully chosen & numerous intercepting catch water drains should be provided which is an important part of the hill drainage system.
If the drainage in hill roads is not adequate & efficient, it will result in complex maintenance problems.
Disadvantages of Road Side Drain
- It increases the cost of road construction
- More formation width of the road is required to construct the road
- Skilled human power as well as equipment will require to lay out the flow of water through the drain.
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