Stick to updated guidelines to minimise urban flooding in India

When we talk about the monsoon today, the first image that comes to mind is waterlogged urban roads. Flooded streets have become a common sight in urban India, leading to increased demands from the public for additional grey infrastructure, such as concrete drainage systems. Experts in the field of urban flooding attribute this issue to the repercussions of climate change, advocating significant alterations in urban planning practises, including the adoption of ‘sponge cities’, which can entail substantial capital investments.

This article aims to shed light on the shortcomings of our drainage planning systems and policymaking.

In 18th-century road construction models like the Tresaguet (France, 1764), Metcalf (France, 1717-1810), and Macadam (in England), drainage systems alongside roadways were built to remove water from pavements and protect roads from water damage. It was intended to capture runoff from highways, not the entire watershed. When the concept of concrete drainage systems was adopted in India after Independence, the availability of open spaces in our urban areas facilitated rapid post-rainwater drainage. However, today, the concrete jungles have diminished the permeability of our urban environments, causing water to flow from catchment areas to road-based drainage systems, causing water logging.

Like other states, Kerala’s building rules (Kerala Panchayath Building Rules 2019 and Kerala Municipal Building Rules 2019) mandated the need for rainwater harvesting systems in all new buildings (except hazardous occupancy buildings). Still, they were to make exceptions for housing units in a plot of less than five cents and/or having a built-up area up to 300 sqm. As the average floor area in Kerala is 90.1 sqm (NSSO report), the amendment exempts a major share of housing units from the rule. While the rule mandates rainwater harvesting systems for new buildings, there are no retrofitting programmes for existing buildings to minimise the stormwater outflow into the roads.

Another significant challenge lies in the design of road drainages. While city stormwater drainage systems adhere to the Indian Roads Congress’ IRC:SP:050, many still adhere to earlier versions of this code. The outdated approach (IRC:SP:50-1999) channels stormwater from road surfaces to water bodies outside city limits, necessitating the construction of extensive drainage channels. The revised code (IRC:SP:50-2013) recommends using open areas and traffic islands to manage stormwater. However, the major challenge lies in the retrofitting of green spaces and traffic islands, which are often elevated compared to road surfaces, hindering effective water drainage. The IRC:SP:50-1999 required higher curbs and traffic islands near roads to avoid water penetration. Even flyover construction uses outdated drainage methods; water from flyovers is collected and linked to manholes to flow into the city's drainage system. This obsolete approach has endured in many cities, leading to the buildup of substantial volumes of stormwater during every rain shower.

The 2013 revision of IRC:SP:050 emphasises rainwater harvesting and offers a complete stormwater management system. The revised code aims to make cities more resilient and sustainable by adopting modern drainage practises, rainwater harvesting, and reassessing outdated design standards. It also requires traffic islands and curbs to include planters and tree trenches for stormwater ground-level drainage, minimising road runoff. The amended rule requires flyover downpipes to be connected to rainwater harvesting systems and excess water to enter the city's drainage system.

The presence of multiple governing agencies responsible for urban space development in our cities makes integrated drainage difficult. Each of these agencies prepares its own plans, such as smart city plans, development area plans, non-motorised transport plans in the metro corridor, and more. These plans often prioritise the development of drainage systems separately, without considering their interrelation. Redesigning these drainage systems, which may not comply with the updated code (IRC:SP:50-2013), is complicated.

To address the issue of urban waterlogging, we must adopt a more sustainable and forward-thinking approach to urban/rural planning and drainage systems. Policymakers and planners should recognise that minimising runoff from built-up areas onto roads is the best method to decrease city waterlogging. Water should move from one location to another, replicating a natural drainage system; therefore, converting all rainwater into stormwater and directing it into the drainage system is not ideal. City stormwater management should begin with individual residences; each building/plot should constitute a rainwater harvesting system, regardless of the plot’s scale. Retrofitting programmes are to be hosted for the existing buildings by providing incentives for incorporating a rainwater harvesting system.

The reconstruction of existing drainages, traffic islands and open spaces along the roadways, aligning with the principles outlined in IRC:SP:50-2013 is necessary. The effectiveness of the practises endorsed in the revised code can only be analysed through practical implementation. A change is required at an administrative level too, aiming to improve transparency among government bodies and ensure that officials are well-versed in the importance of complying with updated codes while designing physical infrastructure.

Nikhil Ali is Research Associate, CPPR.

(Disclaimer: The views expressed above are the author's own. They do not necessarily reflect the views of DH).