© The Indian Express Pvt Ltd
Tags:
Journalism of Courage
Waterlogging in Indian cities: Every monsoon, a downpour is followed by the same scene playing out across most of urban India — knee-deep water on roads, long traffic jams, stranded vehicles afloat in the waterlogged areas and sometimes even the death of commuters and pedestrians. Just a single bout of heavy rain exposes the big gap in the very foundational infrastructure of Delhi-NCR or any city across India — their roads and drains. In suburbs such as Gurugram, touted as a showpiece of India’s economic prowess, most roads periodically turn into waterways.
While there are many factors that lead to water logging in an area, whether the construction of the road and its drainage system was done in a scientific manner holds prime importance. Indian Road Congress (IRC), the premier technical body of highway engineers, has laid down codes and standards for road, highway and drainage construction.
According to the IRC, a road drainage system must satisfy two main criteria for it to be effective throughout its design life — it must drain surface and subsurface water away from the roadway and dispose it off in a way that prevents excessive collection of water in unstable areas and subsequent downstream erosion. The drainage system should be designed in line with the IRC codes namely IRC:SP:42-2014 (Guidelines on Rural Drainage), IRC:SP:50-2013 (Guidelines on Urban Drainage) and IRC:SP-90-2023 (Manual for Grade Separators and Elevated Structures). In addition, the Ministry of Road Transport and Highways’ (MoRTH) specifications for Road and Bridges (5th Revision) under clauses 309 and 704 provide the framework for effective surface and subsurface drainage.
Put together, these clauses and criteria serve as a comprehensive guideline for designing, constructing, and maintaining urban road drainage systems.
Key structures to avoid waterlogging
The IRC guidelines for urban drainage, which were first published in 1999 and revised in 2013, list out a total of seven key structures and their parameters or specifications for an effective drainage system integrated with the roads and highways. These elements are:
In the road surface drainage element, according to the IRC, the minimum desirable longitudinal gradient for satisfactory drainage of pavement shall not be less than 0.50 per cent. A 0.50 percent gradient means that for every 100 m of horizontal distance, the elevation changes by 0.5 m. In practical terms, a 0.50 per cent gradient is a relatively gentle slope. It’s enough to allow water to drain off the pavement surface.
The guidelines further say that a minimum longitudinal gradient of 0.30 per cent is necessary to facilitate the flow of water inside drains, with outlets (such as bridges, culverts, ponds, nallas) provided at required intervals to restrict drain depth.
Similarly, in case of transverse ‘Gradient of Pavement or Camber’, a balance is required between steep gradients for quick dispersal and flatter gradients for driver comfort and safety. The report says that a cross slope of 2 per cent — a gentle tilt of the road surface from the centerline to the edge — will have a minimal effect on driver comfort or vehicle stability. It means for every 100 ft of road width, the elevation change would be 2 ft.
It also says that shoulders should be sloped to drain away from the pavement, with cross-falls of at least 0.5 per cent steeper than the pavement and paved footpaths should have a cross-fall of 3 to 4 per cent, sloping away from the carriageway. The cross-fall on a road, or the camber, is essentially the transverse slope of the road surface, or the slope from the center of the road towards the edges.
When water level increases on the road, the drainage capacity of the tyre tread pattern and pavement surface is exceeded and the water begins to build up in front of the tyre, the occurrence of this phenomenon is called hydroplaning. Hydroplaning can occur at speeds of 80-90 kmph with a water depth of 2 mm, and can force vehicles to skid and trigger accidents. The report says that the effective drainage construction will reduce the hydroplaning potential of the road surface.
Importance of urban drainage
Urban drainage systems, an official said referring to the IRC Code, should be designed to promote infiltration of storm water into the ground starting from street-level drains and continuing through tertiary, secondary, and primary drains. This can be achieved by redesigning existing drainage cross-sections and providing filter mediums (e.g., gravel, sand, perforated polyester fabric like geotextile) or filter beds at alternate junctions, according to the guidelines.
“For efficient functioning of the storm water drainage system, certain appurtenant structures are essential. Storm water drain inlets are used to collect run-off and discharge it to the drainage system. These are the devices meant to admit the surface runoff to the drain and form a very important part of the system. Their locations and design shall, therefore, be given careful consideration. Inlets are typically located in gutter sections, paved medians, roadside and median ditches,” says the IRC code.
Rainwater on flyovers should be drained through an efficient piping network (down-take pipes or pipes embedded in piers) to rainwater harvesting systems or drains, avoiding direct discharge onto the road below. Valley curve areas where ramps meet ground level should have finger plate drains across the pavement.
The underlying pavement should have a downward longitudinal gradient towards the valley junction for efficient discharge into the edge drain. The junction level should be slightly higher than meeting roads to direct water to traffic islands (which can act as rain gardens) and then to the main drainage system.
The IRC code also suggests drainage through pumping in low-lying areas, underpasses, roads under bridges, and certain flyovers where storm water cannot flow by gravity.
Role of local authority
Road construction is a complex process as it involves multiple stakeholders and clearances from many departments. The coordination between the relevant departments, especially local bodies, is necessary to get rid of the problem of waterlogging.
India has the second largest road network in the World of about 63.45 lakh km, comprising national highways (1.46 lakh km), expressways, state Highways (1.79 lakh km), Major District Roads, other district roads and village roads. These roads come under the jurisdiction of multiple authorities such as the National Highways Authority of India (NHAI), National Highways & Infrastructure Development Corporation (NHIDCL), and the Public Work Departments (PWDs), among others.
Thus, the role of local authorities such as municipal corporations becomes important because they have to link the drainage along these highways and roads to the main drainage system of the city.
The matter was also raised during the deliberation of the Parliament’s Public Accounts Committee (PAC) for its report on Levy and Regulation of Fees, Tariffs, User Charges etc. on Public Infrastructure and other Public Utilities.
According to the report — on being asked whether poorly designed or non-continuous drainage systems cause recurrent waterlogging and submergence of adjacent homes and service roads — the MoRTH in a written reply said, “The drainage systems are designed in accordance with MoRTH specifications and IRC guidelines. As per these guidelines, the drains are constructed parallel to the service road to avoid the waterlogging on the road surface and to ensure that the surface water drains off from the Main carriageway and service road without creating waterlogging. However, the reliance is on the local authority to link the drains along the NHs with the master drainage plan and problems occur where the local authority is unable to construct the master drainage for the area.” The PAC report was presented in Lok Sabha and tabled in Rajya Sabha on August 12.
