What Are The Different Types Of Road Drainage Systems? . Roads play a critical role in connecting people, goods, and services. Yet, their durability and usability largely depend on proper drainage systems. Without effective drainage, roads are prone to water damage, erosion, and eventual failure. In this article, we’ll explore the various types of road drainage systems and their significance in infrastructure development.
The road drainage system is used for the removal and disposal of water from the surface as well as subsurface water. It maintains the stability and durability of the road, by keeping it dry as possible. The longer water sits on a surface, the more susceptible it is to contamination. The installation of suitable surface and sub-surface drainage systems is an essential part of highway design and construction.
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Understanding Road Drainage Systems
Definition and Functionality
A road drainage system refers to the network of structures and designs created to collect, transport, and dispose of water from roads. The primary goal is to prevent water accumulation, reduce erosion, and maintain the structural integrity of the road.
Key Functions:
- Redirect excess water from road surfaces.
- Prevent water infiltration that weakens the road base.
- Reduce risks of hydroplaning for vehicles.
Sources of water ingress on roads;
- Capillary action of water
- Rainwater falling on the road surface
- Water accumulated from the surrounding area
- Sub-soil water collection
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Why do we need road drainage?
Road drainage systems are installed to capture surface water run-off to alleviate flooding and protect the surface and sub-surface of the road. It is required for the following reasons:
- Prevent flooding, ponding and seepage
- Keep the carriageway, cycleway and footway free of water
- Keep the underlying road structure as dry as possible.
- Prevent damage caused by hazardous surface water
- Stopping surface water flooding adjacent properties
Defects caused due to improper road drainage
The improper highway drainage leads to the deterioration of the road in the form of the following defects:
- The formation of erosion, causing disembarkment along the roadsides
- Dislocation of pavement edge due to the presence of excess water.
- Stripping of bitumen from aggregates like loosening or detachment of some of the bituminous pavement layers
- Formation of potholes
- Failure of soil slopes because excess moisture causes an increase in weight and
- Formation of waves and corrugations in flexible pavements.
- Softening of subgrade soil bearing capacity
- Reduction in soil mass
- Shoulders are pavement edge distress
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Types of Road Drainage Systems
There are many different types of drainage systems with different design features and attributes that can be used to manage flows and treat water quality. Each of them is discussed below;
1. Surface drainage system
Surface drainage system refers to the drainage wherein surface water is collected and disposed of. It is useful to carry rainwater away from the carriageway. It is applicable in heavy rainfall areas. The water in this drainage system is removed by providing a camber and cross slope to the pavement. The camber and slope depend upon the type of pavement and the intensity of rainfall. This type of drainage system prevents the infiltration of rainwater. includes interception and diversion of water from the road surface. Different types of drainage used for surface drainage systems are :
1- Closed drains
They vary in size and length and can be categorised as:
- Drains provided with gratings
- Jelly drains
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2- Ditches or open drains
They vary in size and length and can be categorised as:
- Shallow surface drains
- Medium-sized drains
3- Side drains
4- Catch basins
5- Inlets
2. Subsurface drainage system
Subsurface drainage is used to remove water that has infiltrated into the soil in excess of the amount. It is useful to carry ground water away from the subsoil. It is feasible in water-logging areas. This type of drainage system helps to keep the pavement layers in dry conditions by avoiding a rise in the groundwater table. Different types of drainage used for surface drainage systems are;
- Subgrade Drain
- Longitudinal Drain Trenches
- Subsurface pipes
- Interceptor drains
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3. Cross drainage system
Cross drainage is provided whenever streams have to cross the roadway facility. The water from the side drains is also often taken across these structures to divert the water away from the road to a water course or a valley. The need for constructing cross-drainage structures arises to ensure that the water flows beneath the road without causing any inconvenience or instability to the highway structure. If you’re intrigued by highway structures, we recommend checking out articles on the topic by Melinda Mcgaughey.
Types of Cross-drainage Structures:
- Box Culverts
- Aqueduct
- Syphon Aqueduct
- Super passage
- Canal Syphon
- Level Crossing
- Canal Inlets and Outlets
- Minor and major bridges
- Causeways
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Requirements of Road Drainage System
Following are the essential requirements of a good highway drainage system:
- The surface water from the carriageway and shoulder should effectively be drained off
- The surface water from the adjoining land should be prevented from entering the roadway.
- The side drain should have sufficient capacity and longitudinal slope to carry away all the surface water collected from the roadway.
- The flow of surface water across the road and shoulders and along slopes should not cause erosion or form cross ruts
- Seepage and other sources of underground water should be effectively intercepted and drained off
- In water-logged areas, special precautions should be taken
- The road surface should be provided with suitable camber to drain off quickly
Defects Caused by Improper Road Drainage
Inadequate highway drainage results in the degradation of the road, manifesting in various defects such as:
- Erosion Formation: Improper drainage contributes to erosion, leading to the disintegration of the road’s edges.
- Pavement Edge Dislocation: Excessive water presence can cause the displacement of the pavement edge, affecting the road’s structural integrity.
- Bitumen Stripping: Inadequate drainage may result in the stripping of bitumen from aggregates, causing loosening or detachment of certain layers in bituminous pavement.
- Pothole Formation: Poor drainage increases the likelihood of pothole development, compromising the road surface.
- Soil Slope Failures: Excess moisture stemming from improper drainage can lead to the failure of soil slopes due to increased weight.
- Wave and Corrugation Formation: Flexible pavements may exhibit waves and corrugations due to insufficient drainage, impacting the smoothness of the road surface.
- Softening of Subgrade Bearing Capacity of Soil: Inadequate drainage can soften the subgrade soil, reducing its bearing capacity and compromising the overall road stability.
- Reduction in Soil Mass: The presence of excess water can lead to a reduction in soil mass, further compromising the road’s structural integrity.
- Shoulder Distress: Improper drainage contributes to distress along the pavement edges, affecting the road’s shoulders.
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FAQs
1. What is the purpose of a road drainage system?
Road drainage systems prevent water accumulation, protect road structures, and enhance safety.
2. How do culverts differ from side drains?
Culverts channel water beneath roads, while side drains collect and divert surface water along road edges.
3. Why are French drains important?
French drains help manage both surface and subsurface water, preventing waterlogging.
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