Urban Flooding and Climate Change
Raghu
FLOODING due to heavy rainfall in major urban centres, which used to be witnessed once in a while, has of late become commonplace, occurring almost annually. Citizens may have thought the situation would improve with economic growth and higher investment in urban infrastructure, but the scenario has clearly worsened.
This is, of course, partly due to climate change which is known to cause extreme rainfall events, an expected outcome of climate change in large parts of the world including South Asia, when large quantities of rain fall in very short periods, overwhelming existing natural and built drainage systems. Reports of the Intergovernmental Panel on Climate Change (IPCC), World Meteorological Organisation (WMO) and the Indian Meteorological Department (IMD) have all predicted that extreme rainfall events are likely to occur more often and also intensify.
However, deeply flawed and structural failures in urban planning and governance are equally if not more responsible for urban flooding. Many experts, urban planners and civil society organisations agree that urban flooding is a result of poor urban planning, worse implementation, patterns of urbanisation driven by dominant real estate and construction interests ignoring all other considerations, rampant degradation of natural drainage and blue-green water absorption systems, and outdated infrastructure with little or no upgradation in step with urban growth. With natural drainage channels blocked, water bodies and green spaces in rapid decline, and non-permeable built-up area now around 90 per cent in most Indian cities, rainwater has no place to go except on to the streets.
Urbanisation has accelerated in India in recent decades, both driving and reflecting economic growth. Urban centres in India generate around 63 per cent of GDP, expected to rise to over 73 per cent by 2030, with an estimated around 35 per cent of the total population in these relatively concentrated areas. Urban flooding especially in the large metros and Tier-1 cities results in heavy and recurrent economic losses from damage to public and private infrastructure, loss of property and productivity, and substantial loss of income, habitat and health status due to higher incidence of vector-borne diseases. These problems affect all sections of the population, but have worse impact on low-income groups and workers in the unorganised sector residing in informal settlements.
Since climate change is a reality and extreme rainfall events are the new normal over the foreseeable future, focus should therefore clearly be on putting in place measures and governance systems for climate resilient urbanisation. Unfortunately, India is far from even acknowledging the structural nature of the problem or initiating meaningful reforms in urban infrastructure and governance. And as the saying goes, it you don’t identify the problem, you can’t fix it!
PLANNING
UNDERMINED
India was expected to follow a planned process of urban development governing land use for residential, industrial, commercial and common purposes, infrastructure and provision of civic services, so that urban growth and development take place in a manner as to provide for peoples needs as per the carrying capacity of the urban area and its hinterland. Most large cities are therefore supposed to develop and institutionalise Master Plans of, say, 20 years duration with provision for revision through a consultative process involving all stakeholders. It is estimated that 38 per cent of state capitals do not have Master Plans, as is the case with 50 per cent of statutory towns. However, the status and actual working of the Master plan process in India is a mixed bag of virtually no plans, weak plans, and plans with poor implementation.
While there are many broader issues involved, for purposes of this article, we will look at those aspects impinging on a city’s ability to cope with urban flooding and climate change.
Delhi’s Master Plan 2041, considered to be among the leading planned urbanisation processes in the country, which was supposed to take a holistic view covering environmental aspects, is currently hanging fire and is yet to be notified. This means that Delhi, with one of the oldest Master Plans in India, is essentially operating without a plan since over a decade or two with urban development taking place through ad hoc bureaucratic decision-making. Meanwhile, large-scale changes of land use are taking place with huge infrastructure such as new arterial roads and elevated stretches, expanding metro rail network, other new infrastructure and accompanying land-use changes, apart from the growing unauthorised and informal settlements amounting to close to half the city, without proper water and sanitation infrastructure and services.
It was expected that in MPD 2041, green spaces and water bodies would be notified and protected to absorb rainwater and reduce run-off contributing to urban flooding as well as to assist groundwater recharge, but this is not happening with any statutory backing. It is evident, however, that the plan itself has very weak provisioning for drainage systems, protection and conservation of natural drainage lines, design of built-up spaces and infrastructure that utilises natural drainage and slope to prevent water-logging. The number and area of water bodies have shrunk and, while plans are being made to conserve at least some of the remaining water bodies, this process is ad hoc.
Chandigarh is fortunate in having been designed as a planned city and zoning is being quite firmly adhered to although strains are beginning to show. However, efforts at conserving and protecting Sukhna Lake, into which most of the city’s storm water drains, has largely prevented Chandigarh from suffering the fate of other large cities.
NATURAL DRAINAGE
CHANNELS BLOCKED
At the opposite end of the scale, Gurugram outside Delhi, which prides in calling itself the “Millennium City” housing leading multi-national IT companies, is a complete disaster and a model of unplanned development. The whole city was actually built on the assumption that the state would take on no responsibility for civic services, and that each private sector developer would take the responsibility for providing electricity and water utilities, as well as providing sewage, drainage and garbage clearing infrastructure and services. The absurdity of numerous developers building and managing their individual infrastructure and services soon became obvious. With no thought given to natural drainage, the city has come up with swanky high-rises but which drown under rainwater mixed with sewage every monsoon. Arterial roads have been built precisely where natural drainage channels used to exist many decades ago, which therefore now become rivers in heavy rains.
Mumbai and Bengaluru are cases of almost total failure of planned urban development. Mumbai is characterised by urban sprawl, blocked pathways of natural drainage, such as the Mithi river leading to the Arabian Sea, and new constructions also interfering with natural drainage, further exacerbating urban flooding. Mumbai has been witnessing extreme rainfall of over 200-300 mm in a day, often falling in just a few hours. As with almost all other cities in India, Mumbai’s stormwater drainage system is under-designed and totally inadequate to cope with such extreme rainfall events.
Bengaluru, the so-called Silicon Valley of India, is being submerged almost every year. Planning is virtually non-existent, with the main city being covered by its own plan while most of the new development, now several times larger than the main city, now not covered by any planned process at all. Once known as the garden city, most new development has witnessed denudation of green cover and open spaces, decreasing ability to absorb rainwater. Bangalore which drains three watersheds once used to have 800-1000 lakes but is now left with only 200-300 which too have shrunk substantially in size. Bengaluru is now starved of water, many areas being dependent on tanker supply and deep-aquifer groundwater, and these lakes no longer have the capacity to store run-off water.
These lakes used to be inter-connected in a large network which stored rainwater and also used to supply water to the city. These inter-connections have been cut off by unplanned or poorly planned development and natural drainage channels have been blocked. Many of these lakes have actually been built over by residential and commercial towers which also discharge untreated sewage and other waste water into these water bodies. The city has no process to regulate these buildings. It has been reported that no government body regulates the height or number of floors or flats in these high-rise towers, with multi-story underground parking that blocks pathways for groundwater recharge. Civic authorities state they do not regulate these structures except for routine building permits and, shockingly, state that there is no method to determine the infrastructure or services, flying in the face of known carrying capacity estimations!
LOW CAPACITY
STORMWATER DRAINS
Another problem common to all cities in India is that stormwater drains are much smaller than required under conditions of extreme rainfall.
Most cities have drains to handle what used to be classified as “heavy rainfall” of 12-20 mm/hour, although in actuality the capacity is much less due to blockage, lack of maintenance and problems in linking up with other drains in the system. However, with climate change bringing extreme rainfall which often sees downpours of 50-100mm/hour, these earlier drains are clearly inadequate.
There is no solution to this except to replace the stormwater drains with larger ones.
Chennai, which has been plagued by urban flooding over the past two decades, is one of the few cities to have embarked on this gigantic task and is planning expenditure of several thousand crores on new stormwater drains of 600x750 size. This task is on-going, and facing complaints from residents, mostly about improper local linkages between drains and a continuing problem of mixing sewage and stormwater drainage lines. Chennai is blessed with three rivers running through the city but has a huge problem of blockage of these rivers, reduction of depth due to silt and garbage.
Delhi’s stormwater drainage system is clearly under-designed and efforts to prepare a Drainage Master Plan have been hanging fire for more than two decades.
No doubt all the above are gargantuan tasks: re-thinking urbanisation and urban planning and governance, work towards city-scale drainage maximising use of natural drainage channels, upgrading stormwater drains delinked from sewage systems, and conserving and ring-fencing blue-green infrastructure. This requires an integrated approach and not knee-jerk or piece-meal measures. It is also clear this will be a costly task. Some estimates have suggested that India will need to spend about many billions of dollars over the next couple of decades to become resilient to climate-related urban flooding in such a way as also assists in other aspects of climate-proofing Indian cities. This is undoubtedly a lot of money. But it will save the estimated losses of $4-5 billion India is incurring annually, likely to go up to $30 billion over the next few decades. And these costs will only keep increasing with each passing year. There is no time to lose.
