The importance of road drainage

As we know water is the most important compound ensuring life on this planet; But on paved roads the presence of water is usually trouble and can be very dangerous.  One of the main causes of road damage, longevity and serviceability of road systems, is presence of excess water filling the pores of road materials.  It is known that road structures perform better in dry conditions, because of this roads historically have been built on dry terrain.  On occasions where roads have had to be built on wet terrain, drainage structures have been designed to keep the road structures as dry as possible.

The first roads in Europe were built about 3,500 years ago.  Already at that time engineers designed the road structures to account for the importance of drainage.  They paid attention to cross-fall (helping water to flow to the lateral ditches), grade line (the road surface should be above the groundwater table and the surrounding ground) and lateral ditches (to convey water away from the road structure and prevent water table rise).

Poor drainage creates many problems for both users and road owners.  Typically these are:

1) Traffic safety (hydroplaning and ice), poor drainage is a safety issue.  Water may accumulate on the road like it does in ponds. Any accumulated water creates a risk of hydroplaning when the roads have rain on them.  A wet road surface reduces friction which leads to longer distances needed to brake vehicles.  Surface water can freeze during the night which can create an ice covered road. When this happens roads may become very slippery and hard to drive vehicles on.

2) Uncontrolled water flows and Culverts on roads can cause erosion.  Small diameter and clogged culverts can cause water to flow towards the road and produce erosion.  Water exiting from culverts can similarly cause erosion when it discharges directly on to erosive soil.  The sensitive soil types for erosion are silt, silty moraine and sand.  Vegetation can actually reduce erosion.

3) Reduced bearing capacity in the sub grade and road structures causing permanent deformation.  Poor drainage and moisture is a main contributor to permanent deformation on roads.  The earlier road projects in the United States have shown that in the Northern Climates permanent deformation is the main cause of undesirable rutting on low travel volume roads.  This can result in reduced traffic safety, increased driver health issues, lowed bearing capacities, and higher costs for road owners and users.

4) Differential frost heaves tend to exhibit poor drainage when the road is not maintained as it should be.  Frost heaves themselves cause unevenness and cracking on road systems.

5) Reduced pavement life time and increased pavement management costs.  The most important factor triggering the need for paving is poor quality drainage.

By improving the drainage conditions during construction and in critical sections of road systems; By maintaining these road systems it will increase the pavement lifetime by 1 ½- 2 times the life span of an unmaintained road.  The conclusion is that if drainage maintenance and  preventative maintenance is done properly it can lead to major savings for owners of roads and parking lots. Saving time and money by annual maintenance costs for paved road systems benefits everyone who comes in contact with these paved roads.

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