The past two decades in India have been witness to recurrent episodes of urban floods. Extreme weather events, coupled with the intensified phase of urbanisation in 2001-11, which has contributed to spatial expansion of urban extents, has greatly increased their frequency (AMRUT, 2017). One can recall the floods that occurred at the beginning of the 21st century, in the month of August 2000 in Hyderabad. Following the floods in Hyderabad, urban floods were recurrently reported across the cities of Delhi in 2002 and 2003, Mumbai in 2005, Surat in 2006, Kolkata in 2007, Jamshedpur in 2008 and Guwahati in 2010 . The most recent urban floods were recorded in Srinagar in 2014 and Chennai in 2015 (AMRUT, 2017). During the 2014 floods in Srinagar, over 200 people lost their lives and water reportedly stood at a depth of 12 feet in low-lying areas. In 2015, floods in Chennai brought the entire city to a standstill, with a death toll of 280 (Iyengar, 2015).
Urban flooding is fast becoming one of the most frequently occurring human induced disasters. The problems posed by urban floods can range from localised or contained incidents, where the damage to life and property is minimal to far reaching that cause widespread inundation and brings life to a standstill. This leads to temporary relocation, threats of outbreak of epidemics, loss of livelihoods and impacts civic infrastructure adversely. Urban floods are likely to be more severe as compared to those occurring in rural areas, as urbanisation can increase the risk of flooding by up to three times (Rafiq et al., 2016). Dense population clusters in cities impact a larger number of people and severe losses are incurred by industrial and commercial establishments.
Urban Floods: The Causes and Effects
Floods are defined as the submergence of a usually dry area by a large amount of water that comes from sudden and excessive rainfall, overflowing of river or lake, melting of snow or exceptionally high tide (AMRUT, 2016). When occurring in urban areas, the effects of floods increase manifold, causing massive damage to life and property—crippling commerce and basic civic facilities.
By their very nature, urban floods can be categorised as human induced disaster, caused by constant meddling with natural streams, watercourses, encroachment of water bodies, and unchecked urbanisation (NDMA, 2010). Factoring in climate change, the effects of urban floods are likely to be exacerbated in the near future. Research suggests that climate change will lead to increase in short duration precipitation, cause short bursts of intense rainfall and pose major challenges to storm water design (Ali, Pai and Mishra, 2014). In the years between 1901 and 2010, only four of the total 57 urban areas have shown a significant trend in monsoon maximum rainfall (MMR). However, in the period between 2010 and 2060, MMR is likely to increase significantly at 1 to 3 day durations. The number of urban areas where increased rainfall is likely to occur is far larger than the number of areas that experienced these changes between 1901 and 2010 (ibid). The current practices of urbanisation in India are not conducive to prevent or mitigate urban floods.
The relatively flat terrain on either side of the river channel that get submerged during floods—the floodplains, are areas where a variety of riverine features are built by sediments which are derived from the upper reaches of the drainage basin and deposited further downstream. Floodplains are also responsible for groundwater recharge. Unchecked construction of buildings, temples and highways has transformed the natural soil cover into concrete surfaces, considerably reducing groundwater recharge. This in turn creates impervious surfaces that obstruct natural floodways and increases the rate and volume of runoff (Raymahashay and Sinha, 2016). Increased frequency of floods is a direct consequence of fields or woodlands turned into roads and parking lots—concretised surfaces do not have the capacity to absorb rainfall. Conversion of water bodies to residential layouts has intensified this problem by removing the interconnectivities of water terrain.
A case study in the city of Bengaluru has noted that the lack of planning and unchecked urbanisation has caused the filling up of floodplains, reduction in catchment area and narrowing of waterways (Ramachandra, Aithal and Kumar, 2012). This has subsequently caused recent flooding in areas that do not show any earlier records of being flooded. Further, lakes in the city have been appropriated for developmental activities, disrupting the natural movement of water between different areas of the city. Analyses of drainage networks between Ulsoor and Bellandur, for instance, revealed that after the Challaghatta Lake was converted into a golf course, the drainage network between these two localities had been lost (ibid). In the 1960s, 262 lakes existed in the city, but presently, not even 10 are in a healthy state (Sengupta and Sengupta, 2016). Field surveys of lakes in the city have shown that over 66 per cent of them are sewage fed, 14 per cent are surrounded by slums and 72 per cent have shown a significant loss of catchment area (ibid). Last year, the Indian Space Research Organisation (ISRO) overlaid maps of the city from 1965 over those from 2017 and found that while earlier there were at least 1,397 km of drains in the City, the figure had been later reduced to 1,105 km (Rao, 2018). While effects have not yet been felt at a large scale in Bengaluru, experts have warned that this unchecked urbanisation is likely to have major repercussions. During the recent floods in Karnataka, Kodagu district was ravaged by 1,657 mm (till August 21, 2018) of rainfall (TNN, 2018). On August 17, 2018, the district received 300 mm of rainfall in a single day. If Bengaluru receives even 10 per cent of this rain, it could potentially devastate the city; in fact a mere 30 mm of rainfall for 30 minutes is likely to cause flooding, especially in the low lying areas (Rohith, 2018).
Past experiences strengthen these dire predictions. In July 2005, when Mumbai received >200mm rainfall (classified as ‘very heavy’ by the Indian Meteorological Department), various parts of the city were inundated to varying degrees and 419 human lives were lost. The underlying causes for the rapid flooding in the city were the erection of slums along places of outfalls and loss of detention ponds to development (Gupta, 2007).
The case of flooding in Chennai in the year 2015, where the death toll was 218 and economic losses computed at INR 15,000 crore serves another example of the dangers of rapid urbanisation (Thangavelu, 2015). The rainfall received by the city in the month of November 2015 was ~48 inches, with mismanaged urban development compounding the effects of an extreme weather event caused by warm seas and long distance effects of the El-Nino (NASA Earth Observatory, 2015). In the years between 2006 and 2016, Chennai has witnessed seven episodes of urban floods (Sengupta and Sengupta, 2016). In 2014, an analysis conducted by the Indian Institute of Science (IISc) found that since the 1970s, urbanisation in the city increased almost 20 times. Consequently, the city has lost over one-fifth of its greenery (Aithal and Ramachandra, 2015). Green areas were converted to concrete surfaces that increased the runoff and created water logging in the absence of proper drainage. The primary floodwater sink in the city, the Pallikarni marsh, which was around 5,000 hectares (ha) at the time of independence had been reduced to a mere 600 ha by 2011 (Gopalakrishnan, 2016). A complete disconnect between hydrology and urban planning were found in Chennai, which caused steady drop in the water table. Moreover, recharge structures like lakes, tanks, ponds and other wetlands have been disregarded and the natural course of water has been stymied. This has been one of the major causes of flooding in the urban and peri-urban areas (Sengupta, 2015).
Speaking with G’nY, Anant Maringanti, Director of Hyderabad Urban Lab, notes, “The problem arises with the unchecked development of real estate in cities and infrastructure creation that does not take into account gradient and topography. Older agricultural practices have disappeared—wetlands serve no economic purpose today and we have been unable to find an alternative use for them. Since it is not possible to bring in older practices into the city, it is pertinent that we develop newer practices that can reinforce recharge and minimise risk.”
There is an urgent need to preserve city catchments to curb incidents of urban flooding. Corrective measures need to be taken immediately—else urban floods are likely to become a norm rather than an exception (Bhushan, 2016). The first step to check incidents of urban flooding is the preservation of urban lakes and catchments, which needs a robust legal framework. At present, no such framework exists to challenge encroachment of lakes, floodplains, or other catchments in urban areas, despite the fact that this issue has been raised by the Supreme Court, most significantly in the case of Vasundhra Pathak Masoodi vs Union of India, where it was observed that massive encroachments and erection of many structures and hotels have led to the reduction in the size of lakes in Srinagar. The River Regulation Zone, conceptualised on the lines of Coastal Regulation Zone in 2012, is still to see the light of the day. There have been numerous judicial interventions where the Courts have ordered to declare a no development zone in floodplains and riverbeds. In July 2017, the National Green Tribunal (NGT) ordered that an area of 100 m from the edge of the Ganga between Haridwar and Unnao was to be a no development zone. Dumping of waste within 500 m of the river and into the river was prohibited and any violators were to be fined INR 50,000 (NGT, 2017). Despite this ruling, the practice continues uninhibitedly—over 1.3 billion litres of waste flows into the river everyday (Jadhav, 2018).
But examples of courts noting the importance of floodplains and wetlands are not recent. In 1992, a proposal for the construction of World Trade Centre was challenged in the Calcutta High Court (HC). It was held that bheris—as wetlands are termed in Bengal—are important for maintaining ecological equilibrium and the state government was directed to stop all encroachment occurring in wetlands in order to preserve their nature and character (Calcutta HC, 1992). Judicial orders, however, can only intervene in individual incidents of encroachment. To put an absolute check on encroachment of floodplains and wetlands, a legal framework needs to be put into place.
But the law alone will not suffice. “We also need a change in our institutional framework to ensure preservation of wetlands. Certainly, a law needs to be developed to set up this framework, but this will be only the first step. We need to rethink our culture of governance and institutions, which, in their present state are completely incapable of dealing with the problems. Take the example of accountability for wetlands—there is no one institution from whom this can be sought. The irrigation department is responsible for drainage in the city, the revenue department maintains land records and there are similar bodies that are assigned different functions. This practice needs to change,” Maringanti adds.
It is therefore safe to conclude that the central problem, as far as urban floods are concerned, is the rapid disappearance of wetlands and catchments. Urbanisation and development, which includes the setting up of concrete structures and buildings, paying no heed to the spaces in cities responsible for maintaining ecological equilibrium, needs to be challenged. New practices, including that in governance and city planning need to be developed. In the absence of these, as extreme events occur due to climate change, the occurrence of urban floods is bound to increase.
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