System failure in Asian cities: Chennai, India
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CONTENT 1.
Abstract
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2.
Introduction
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3.
3.1 The Degradation of the hydrological system
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3.2 The Degradation of the ecological system
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3.3 The impact of the degradation of the blue and green systems
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4.Discussion
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5.Conclusion
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1.0 Abstract The mutual yet conflicting relationship between natural hydrological and ecological systems and manmade interventions has been studied in this paper. Chennai, a city located in the South of India, has been studied to understand the degradation of these systems due to various factors and their impacts. Chennai was earlier mostly swamps, marshes and waterways and they formed the natural drainage patterns. However the transformation of this land due to urbanization adversely affected its efficiency and caused flooding, contamination and eventually reduction of the systems in terms of area and richness. The urbanization of Chennai has been rapidly increasing, from 34.15% in 1991 to 48.45% in 2011. Chennai being one of the metropolitan cities in India, has seen rapid transformation and urbanization through the years. It stands as the fourth largest metropolis in India .Developments including residential, commercial and industrial, along with slums have taken a toll on the hydrological and ecological systems. Pollution of the water due to dumping of solid waste, increase in settlements along the river banks and release of effluents from industries are some of the major causes. The hydrological networks consists of the river, its tributaries an interesting rapport between temples and the hydrological system can be distinctly seen in the city. The city was once home to 39 temple tanks that formed a part of the hydrological system. These tanks apart from being sacred, acted as rain water harvesting measures, curbed flooding and recharged ground water. The city is left with only a few that have not dried up or been covered. The city’s wetlands that covered large expanses of land, were once the natural aquifers of the city and acted as detention basins, recharged the ground water as well as a flood mitigation measure. These wetlands today face threat to extinction due to rapid urbanization.
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2.0 Introduction Chennai, one among the four largest metropolitan cities in India, has an area of 1189 km2, with a population of approximately 9 million people, including the city and suburbs, as of 2016.The central areas of the city are rapidly increasing in density, while the peripheral areas are expanding with low density developments. As mentioned in the paper by Murawski (2015), the high density area in the central part of the city increased from 81.32 sq.km to 330.30 sq.km in 2014, while the peripheral areas increased from 53.79 to 303.14 sq. km. Growing at 25% per year, including urban sprawl, its ecological and hydrological systems faced threat of fragmentation and inefficiency, leading to flooding, water contamination and clogged sewers.
Figure 1 Urban developement from 1989 to 2014
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This paper studies the degradation of the hydrological and ecological systems from 1989 to 2012. An estimate of how the systems could be affected in the year 2024 can be taken to understand the impact this will have if the right measures are not taken. Chennai’s hydrological network comprises of both natural and manmade systems. Three rivers, Kosasthaliyar, Cooum and Adyar and one wetland marsh, Pallikaranai, which connects to 31 other water bodies, comprise the natural systems. The manmade systems comprise of the Buckingham canal which connects all the rivers. Additionally there are four reservoirs, Chembarambakkam, Cholavaram Poondi and Red hills, which have a total capacity of 314 cubic meters Chennai was home to a large number of temples, which comprised of stepped temple tanks. The temple which is central in location, acted as a focal point, with settlements developing around it. The city currently has 39 temple tanks. These tanks are for storage, flood mitigation and ground water recharging purposes.The residents depend on these tanks for water supply and for sacred purposes. Many of these tanks have dried out and diminished in use, due to urbanisation and withdrawal of water. As examples, the Mylapore Temple tank and Thirupporur temple tanks have been studied by Madhavi Ganesan in her paper, “The temple tanks of Madras, India: Rehabilitation of an ancient technique for water storage.” Chennai is one of the least green metropolitan cities in India, with only 4.5% of the city’s area being green cover as of 2011. The green network consists of wetland marshes, national parks, street planting and private green areas. The wetlands comprise of Pallikaranai (80 sq. km), Pulicat Lagoon (184 sq. km), Madhavaram and Manali jheels (0.28 sq. km), along with other smaller marshes. The Guindy National Park with an area of 270.57 hectares, which is under reserve forest category. These wetlands face threat to extinction due to new developments, solid waste disposal into these areas, encroachment of informal settlements, industrialisation and extension of the road network. Silting of these areas also led to further depletion of the ground water levels
3.0 The degradation of the hydrological network
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Figure 2 Chennai's hydrological system
Urbanisation has had many consequences on the hydrological and ecological systems. This can be clearly seen in the case of Chennai city. The infiltration component of the hydrological has seen reduction, and therefore increase in run off discharge. Water bodies, which were once detention basins have also dried up causing reduction in detention capacity. Some examples, clearly showing the result of urbanization in the city. The construction of the Mass Rapid Transit System along the Buckingham canal.Construction interrupts the network and causes fragmentation, thereby leading to a lack of efficiency of the navigation canal. The Kamaraj Port, has built large expanses of parking space on the canal’s banks, which disrupt the flow of water through the canal, especially when there is an increase in volume during the monsoon season. This also increases the impervious surface, reducing detention capacity of the wetland. The Buckingham canal has been reduced in width from 25 m to 10 m in the south of its length. The Adyar River has a length of 40 km and it flows into the Bay of Bengal to the south of the city, to Adyar creek. Kallampadu, Pillapakkam and Kavanur are three main tanks that originate from the river, while its sub basins include Chembarambakkam, Sriperumpudur and Pillapakkam and about 100 minor tanks. The river is seasonal and can carry discharge during the monsoon seasons for four months from October to December. A part of the runway of the Chennai airport has been built over the Adyar River and faced severe damage during the floods in 2015. The river has a sand bar at its mouth, curbing free flow of the river. Two check dams on the river were constructed with the intention of recharging ground water. This however is only helpful during drought and not during floods. Interruptions in the hydrological network were also noticed in the Koyambedu drain and the channels from Korattu and Ambattur tanks are missing. Some vital retention tanks namely the Virugambakkam, Padi and Villicakkam tanks have been left abandoned.
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Figure 3 The flooded runway in Chennai a portion of which was built across Adyar river
Adyar Estuary and Creek with its low salinity and abundant plankton, made it fit for fish breeding, making it a rich ecological area. The sand bar located at the Adyar creek also made it difficult for the exchange of water between the river and the estuary takes place only during the peak tides. The estuary however gets contaminated due to untreated waste water from the drains in the city flowing into effluents from the Pammal region and waste from the slums that have developed along the river. Some more manmade interventions that have caused damage are, the culverts, with low capacity built across the newly built roads. The other is construction of the compound walls built around each development of land for privacy and safety reasons, pose threat by altering the flow of water and local flooding pattern. Sometimes the walls also collapse during heavy rains due to pressure exerted by the water.
Figure 4 Buckingham canal in the early days
Figure 5 The MRT line built along the Buckingham canal
It also faces issues of pollution, taking in 60% of the untreated sewage on a daily basis, from the settlements and industries along the canal. Earlier, Tamil Nadu, where rainfall was relatively low, consisted of “erys�, temple tanks and ponds that were measures for storm water detention and rain water harvesting. Temple tanks apart from being sacred, were also used for storage of rainwater, recharging ground water, a flood control measure preventing soil erosion and retaining run off, while also retaining the ecosystem. The surface area of these tanks varies from 2000 sq. m to 30,000 sq. m. Due to development of residential and commercial areas on the catchment areas of the tanks, these areas get blocked and storm water is lost into sewers. Most of these erys are lost, as they were built over.
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The temple tanks were designed with inlets and outlets, such that they were connected to the neighbouring tanks, to take in any excess run off. The only water resources available to the temple tanks in the urban locality are rain water from roof tops, roads and platforms. In actual, the area was previously 70% to 80% open space through which rain water recharged into the ground. Now 90 % of the urban area around the temple is impervious surface.
3.1 The degradation of the green system The city with least green cover, Chennai, was once home to large expanses of wetlands and nature reserves, which now face the threat of extinction. The Pallikarnai wetland marsh, covers an area of 80 sq.km, and is the natural aquifer of the city. It is also the only surviving wetland ecosystem. This wetland is home to 337 species of flora and fauna, as stated by Dr. Jayshree Vencatesan, in her paper, Protecting Wetlands. The marsh also provides habitat space for migratory birds for foraging and breeding. Some endangered birds, for example, the gloss ibis, the grey headed lapwings and pheasant tailed jacanas can be spotted here. Also some endangered reptiles, like the Russel’s viper, can be spotted. Fish that are widely bred like dwarf gaurami and chromides. The mud crab, mullet, the window pane oyster, half beak and green chromide can also be found here can also be found in the wetland naturally.
Figure 6 Pallikaranai wetland,home to the Purple Suamphen Figure 7 Pallikaranai wetland,home to the Russel’s viper Moorhen
This wetland which is amongst the urban sprawls from the Velachery, Pallikaranai and Navalur areas is at risk of dissappearing. As described by ecologist Shekar Dattatri, in a newspaper article (The Hindu, Jan 2012), “The water is severely contaminated with untreated city sewage, and the mountains of unsegregated garbage contain a deadly cocktail of organic and poisonous waste. Leaching toxins build up in the food chain, poisoning the birds. Undoubtedly, many of these innocent winged visitors die prematurely from the effects of these poisons.” The Madhavaram and Manali Jheels, located 16km north of Chennai has an area of 0.28 sq. km. These marshes are home to fish namely tilapia, freshwater gastropod, apple snail and some insects such as dragonflies, water skater, and keel back water snakes. Some migratory species and other birds like the pheasant tailed jacana, sandpipers, snipes and stints to name a few. This wetland has an inflow of effluents flowing into it from the Madhavaram Dairy, causing oxygen depletion in the water, leading to high mortality rates of the fish due to asphyxiation. The wetland had a sloping terrain in the mid-1990s, but with digging by locals for harvesting fish, it uprooted vegetation and no more provided a habitat for the jacanas. The Pullicat Lagoon with an area of 184 sq. km is the second largest brackish water lake in India. It receives fresh water from the Swarnamukhi, the Kalangi, the Araniar and the Royyala Klava rivers and 8
sustains a diverse variety of flora and fauna. Aquatic species like the, mud and lagoon crabs, mullets, white and tiger prawns, oysters and clams along with over 50 species of birds are found here. Other than these, mangrove species and some crops like paddy and cashew can be found here. This lagoon is being damaged due to the development of the North Chennai Thermal Power Station and the Encore Satellite Port and a petrochemical complex. Toxic fly ash, from the power station, in the form of slurry and hot water are let out into the Buckingham canal, causing siltation in the lagoon. The lagoon supports a fishery, however there has been a drastic decrease in production due to loss in ecological balance. The Guindy National Park has an area of 270.57 hectares, and falls under the nature reserve category. It has tropical dry evergreen vegetation. The biodiversity rich park boasts of 350 species of flora, 100 species of birds, 60 species of butterflies and spiders. This nature reserve in recent times, has a potential danger of loss due to institutions wanting to take up the land and build over it. Indian Institute of Technology (IIT-M), Chennai has already built over 52 acres, felling up to 8000 trees. In 2010, environmentalists managed to stop the construction of a hospital in the premises of the park, averting further damage. More development would only mean loss of habitats and species.
Informal settlements along these water bodies and around marshes contribute to solid waste being dumped into the water and eventually the river.
3.2 The impact of the degradation of the blue and green systems The degradation of the hydrological systems has had many impacts on the environmental and safety front. One of the biggest impacts has been the floods that has affected the city causing havoc. The causes of flooding are urban sprawl that has spread uncontrollably, along with loss of natural drainage. The city which only has 855 km of storm drains as compared to 2847 km of urban roads. This extent of roads also increases the area of impervious surface, along with paving of pathways, parks and open areas. The authorities also play an important role to avert these situations, but lack of effort and integration between authorities further worsens the condition. As seen in the figure 7, maps from 1997 to 2001, green cover of Chennai city saw a significant decrease, due to replacement of dense urban settlements. Due to this, the water holding capacity also went down, and along with increase in impervious surfaces, there was 89% increase in peak flow at certain areas. Ground water recharging reduced drastically due to reduction in retention capacity and increased run off. This brought the ground water level down by 10m from 1997 to 2001. Some parts of the city saw up to 33% decrease in ground water reduction. The Figure 8 shows the situation of flooding in the year 1976 and the year 2005. The inundation map of the Adyar River clearly indicates an increased risk of flooding, around the river banks.
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Figure 7 Urban development from 1989 to 2012
As per the study done by Vijayalakshmi Rajendran and Toshiyuki Kaneda. Chennai was mapped from 1989 to 2012 to understand the changing land cover. The Figure 7 indicates the changing land use and from computations and from computations, the results indicate that in 1989, the urban areas increased from 16% to 44% in 2012. Cropland has decreased from 38% in 1989 to 31% in 2012.
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Figure 8 the above 2 maps indicate the flood inundation change from 1976 to 2005
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Figure 9 Mapping of the Pallikaranai wetland indicating (1) Location (2)Decrease in area (3) Landform (4) Water holding capacity of the wetland
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As studied by Prem V, of CareEarth Trust, Chennai over the span from 1980 to 2010, the city’s wetland percentage has dropped from 80% to a miserly 15%. The built up area computed was only 47.62 sq.km in 1980 with 186.30sqkm of wetlands. Then a drastic change was seen in 1991, where the built up area went up to 152.33 sq.km and the wetlands were now 159.41 sq.km. In 2000, the built up area further increased to 250.58 sq.km, while the wetlands saw a steady decrease going down to 117.48 sq. km. In 2010, the built up area rose to 402.10 sq.km (85%) and the wetlands fell to a measly 71.05 sq.km (15%)
(1)
(2)
http://www.frontline.in/the-nation/rain-ruin/article7911881.ece
(3) Figure 10 (1) People being ferried by boats (2) Buildings submerged (3) Pollution and contamination of the canals
4.0 Discussion The natural hydrological and ecological systems have seen profound change in their life journey and with time have only deteriorated in the case of Chennai. This extensive, fast growing metropolitan city is seeing roadblocks in its planning of manmade interventions to improve the conditions. The measures taken by agencies are not in adherence with adequate planning of the consequences. The airport which was flooded during the 2015 floods, is a clear example of why the city’s planning needs to be done in a sensitive manner to avoid these disasters from striking. Water management and waste water treatment needs to be given Madhavi Ganesan in her paper, “The temple tanks of Madras, India: Rehabilitation of an ancient technique for water storage”, discussed how the temple tanks could ideally harvest 1,300,000 cubic meter of rain water and thereby conserve it. And these could act as potential storage in Urban settings as well, assuming the catchment areas to be ten times the size of the tank itself. The calculation for the rain water collected, taking 1200mm as the normal rainfall, could be 0.6 meters, while the rest of the water could be the run off from the catchment areas. The Adyar estuary, the Pallikaranai wetlands and other ecological areas need attention to be restored. Currently these areas are only moving towards becoming potential backyards of the city.
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Figure 11 A predicted 2024 plan of Chennai city
As per the study done by Vijayalakshmi Rajendran and Toshiyuki Kaneda, the projected scenario,in the year 2024,(Figure 11)shows that with Chennai growing at its current alarming rate, the urban will increase from 44% to 74%. This result can give insights into several possibilities that can occur in the future, and predictions of how the hydrological and green systems of the city will be affected.
5.0 Conclusion Chennai like most other rapidly urbanizing cities is facing issues, leading to a fragmented network and inefficient natural and manmade systems. The impacts of these were clearly seen in the year 2015, when it faced flooding, displacing homes, people and livestock. Land use can play a vital role to deeply examine retention areas, rain water harvesting potential and help in flood risk mitigation. Biodiversity hotspots and ecologically rich areas need policies and regulations to be conserved and protected from invading development and improper waste management methods. Awareness about these issues amongst the residents and authorities of the potential risks involved in urban planning must be carried out, as some existing settlements cannot be demolished or relocated. Instead a constructive framework of regulations will lead to sustainable change.
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References
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