Importance of Highway drainage system

Provision  for  adequate  drainage  is  of  paramount  importance  in  road  design  and  cannot  be overemphasized. The  presence  of excess  water  or  moisture  within  the  roadway  will  adversely affect  the  engineering  properties  of  the  materials  with  which  it  was  constructed.  Cut or fill failures,  road  surface  erosion,  and  weakened  sub-grades  followed  by  a  mass  failure  are  all products  of  inadequate  or  poorly  designed  drainage.  As has been stated previously, many drainage problems can be avoided in the location and design of the road: Drainage design is most appropriately included in alignment and gradient planning.

 

Importance of Drainage

Water has a number of unhelpful characteristics which impact on highway performance.

1. It is a lubricant reducing the effectiveness of tyre grip on the carriageway wearing surface which can increase stopping distances.
2. Spray from rainwater being thrown up by car tyres can reduce visibility which can lead to delays in reacting to events on the carriageway.
3. Drag on car tyres from local rainwater ponding can alter the balance of vehicles traveling at speed which can be alarming or cause skidding.
   
   
4.  It is incompressible therefore standing water effectively acts as a jackhammer on the wearing course right through to the sub-base when vehicles pass over head.
5. It expands when frozen pulling apart the carriageway construction which then falls apart when it warms up.
6. In extreme storms, rainwater can simply wash away roads on embankment should the culvert become blocked or lack capacity.