Waterlogging in Indian cities: Each monsoon, a downpour is adopted by the identical scene taking part in out throughout most of city India — knee-deep water on roads, lengthy visitors jams, stranded automobiles afloat within the waterlogged areas and generally even the loss of life of commuters and pedestrians. Only a single bout of heavy rain exposes the large hole within the very foundational infrastructure of Delhi-NCR or any metropolis throughout India — their roads and drains. In suburbs reminiscent of Gurugram, touted as a showpiece of India’s financial prowess, most roads periodically flip into waterways.
Whereas there are lots of elements that result in water logging in an space, whether or not the development of the highway and its drainage system was achieved in a scientific method holds prime significance. Indian Highway Congress (IRC), the premier technical physique of freeway engineers, has laid down codes and requirements for highway, freeway and drainage development.
In keeping with the IRC, a highway drainage system should fulfill two fundamental standards for it to be efficient all through its design life — it should drain floor and subsurface water away from the roadway and dispose it off in a means that stops extreme assortment of water in unstable areas and subsequent downstream erosion. The drainage system needs to be designed according to the IRC codes specifically IRC:SP:42-2014 (Pointers on Rural Drainage), IRC:SP:50-2013 (Pointers on City Drainage) and IRC:SP-90-2023 (Handbook for Grade Separators and Elevated Buildings). As well as, the Ministry of Highway Transport and Highways’ (MoRTH) specs for Highway and Bridges (fifth Revision) below clauses 309 and 704 present the framework for efficient floor and subsurface drainage.
Put collectively, these clauses and standards function a complete guideline for designing, establishing, and sustaining city highway drainage programs.
Key buildings to keep away from waterlogging
The IRC tips for city drainage, which had been first printed in 1999 and revised in 2013, listing out a complete of seven key buildings and their parameters or specs for an efficient drainage system built-in with the roads and highways. These parts are:
- Highway floor drainage
- Storm water administration practices
- Storm water drainage system and appurtenances
- Sub floor drainage
- Drainage of particular places
- Rain water harvesting (RWH) in buildings
- Drainage via pumping.
Within the highway floor drainage component, based on the IRC, the minimal fascinating longitudinal gradient for passable drainage of pavement shall not be lower than 0.50 per cent. A 0.50 % gradient signifies that for each 100 m of horizontal distance, the elevation modifications by 0.5 m. In sensible phrases, a 0.50 per cent gradient is a comparatively light slope. It’s sufficient to permit water to empty off the pavement floor.
The rules additional say {that a} minimal longitudinal gradient of 0.30 per cent is important to facilitate the movement of water inside drains, with retailers (reminiscent of bridges, culverts, ponds, nallas) supplied at required intervals to limit drain depth.
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Equally, in case of transverse ‘Gradient of Pavement or Camber’, a stability is required between steep gradients for fast dispersal and flatter gradients for driver consolation and security. The report says {that a} cross slope of two per cent — a mild tilt of the highway floor from the centerline to the sting — can have a minimal impact on driver consolation or car stability. It means for each 100 ft of highway width, the elevation change could be 2 ft.
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It additionally says that shoulders needs to be sloped to empty away from the pavement, with cross-falls of at the very least 0.5 per cent steeper than the pavement and paved footpaths ought to have a cross-fall of three to 4 per cent, sloping away from the carriageway. The cross-fall on a highway, or the camber, is basically the transverse slope of the highway floor, or the slope from the middle of the highway in the direction of the perimeters.
When water degree will increase on the highway, the drainage capability of the tyre tread sample and pavement floor is exceeded and the water begins to construct up in entrance of the tyre, the incidence of this phenomenon is named hydroplaning. Hydroplaning can happen at speeds of 80-90 kmph with a water depth of two mm, and might power automobiles to skid and set off accidents. The report says that the efficient drainage development will scale back the hydroplaning potential of the highway floor.
Within the highway floor drainage component, based on the IRC, the minimal fascinating longitudinal gradient for passable drainage of pavement shall not be lower than 0.50 per cent.
Significance of city drainage
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City drainage programs, an official mentioned referring to the IRC Code, needs to be designed to advertise infiltration of storm water into the bottom ranging from street-level drains and persevering with via tertiary, secondary, and first drains. This may be achieved by redesigning current drainage cross-sections and offering filter mediums (e.g., gravel, sand, perforated polyester cloth like geotextile) or filter beds at alternate junctions, based on the rules.
“For environment friendly functioning of the storm water drainage system, sure appurtenant buildings are important. Storm water drain inlets are used to gather run-off and discharge it to the drainage system. These are the gadgets meant to confess the floor runoff to the drain and kind an important a part of the system. Their places and design shall, due to this fact, be given cautious consideration. Inlets are usually situated in gutter sections, paved medians, roadside and median ditches,” says the IRC code.
Rainwater on flyovers needs to be drained via an environment friendly piping community (down-take pipes or pipes embedded in piers) to rainwater harvesting programs or drains, avoiding direct discharge onto the highway under. Valley curve areas the place ramps meet floor degree ought to have finger plate drains throughout the pavement.
The underlying pavement ought to have a downward longitudinal gradient in the direction of the valley junction for environment friendly discharge into the sting drain. The junction degree needs to be barely increased than assembly roads to direct water to visitors islands (which might act as rain gardens) after which to the principle drainage system.
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The IRC code additionally suggests drainage via pumping in low-lying areas, underpasses, roads below bridges, and sure flyovers the place storm water can’t movement by gravity.
Function of native authority
Highway development is a posh course of because it includes a number of stakeholders and clearances from many departments. The coordination between the related departments, particularly native our bodies, is important to eliminate the issue of waterlogging.
India has the second largest highway community within the World of about 63.45 lakh km, comprising nationwide highways (1.46 lakh km), expressways, state Highways (1.79 lakh km), Main District Roads, different district roads and village roads. These roads come below the jurisdiction of a number of authorities such because the Nationwide Highways Authority of India (NHAI), Nationwide Highways & Infrastructure Improvement Company (NHIDCL), and the Public Work Departments (PWDs), amongst others.
Thus, the function of native authorities reminiscent of municipal firms turns into necessary as a result of they need to hyperlink the drainage alongside these highways and roads to the principle drainage system of the town.
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The matter was additionally raised in the course of the deliberation of the Parliament’s Public Accounts Committee (PAC) for its report on Levy and Regulation of Charges, Tariffs, Person Fees and so forth. on Public Infrastructure and different Public Utilities.
In keeping with the report — on being requested whether or not poorly designed or non-continuous drainage programs trigger recurrent waterlogging and submergence of adjoining houses and repair roads — the MoRTH in a written reply mentioned, “The drainage programs are designed in accordance with MoRTH specs and IRC tips. As per these tips, the drains are constructed parallel to the service highway to keep away from the waterlogging on the highway floor and to make sure that the floor water drains off from the Principal carriageway and repair highway with out creating waterlogging. Nevertheless, the reliance is on the native authority to hyperlink the drains alongside the NHs with the grasp drainage plan and issues happen the place the native authority is unable to assemble the grasp drainage for the realm.” The PAC report was offered in Lok Sabha and tabled in Rajya Sabha on August 12.