Amphibious Chennai: Systemic Approach to Water Sensitivity by Amreen Imtiaz

Author: AMREEN IMTIAZ M.Sc- Sustainable Architecture & Landscape Design Politecnico di Milano

Supervised by: Prof. LAURA POGLIANI Department of Architecture & Urban Studies Politecnico di Milano Prof. PAOLO DEBIAGGI Department of Architecture, Built Environment & Construction Engineering Politecnico di Milano

INTRODUCTION The aim of the thesis is to explore the relevance of green infrastructure in imparting water resilience of Chennai and propose strategies that allow for the integration of green infrastructure, following a strategic approach- proposing interventions at various scales rather than tackling issues at the symptomatic level. Chennai, like most Asian cities, totters between instances of cloudbursts and dry spells, the worst of which were experienced in the recent past2015 and 2019 respectively. These problems if not addressed immediately, pose a serious question of water security that may be exacerbated exponentially given the threat of Climate Change. Therefore, this thesis proposes solutions for water-sensitizing Chennai, and revitalizing the Cooum river while elevating the public realm along the river within the city. The project adopts a holistic approach giving due consideration to ecological parameters which is lacking in the city’s current developmental planning. Why the Cooum river? Chennai(Madras) was established on the banks of the Cooum river, and as such has great historical significance for the city.

1 2

3 4

1. 2. 3. 4. 5. 6. 7. 8.

5 6

Gummidipoondi Araniyar Nagariyar Nandhiyar Kosasthalaiyar Cooum Adyar Kovalam

Bay of Bengal

Chennai sub-basins The Cooum river basin is a linear basin stretching across the city extent, with a much smaller drainage area and hence the planned interventions can be realised in comparatively lesser duration, serving as a pilot project for similar interventions in the rest of the city.

As a result, the project will inherently also address problems pertinent at the city-scale such as Urban Heat Islands, depletion of ground water resources, and solutions to social issues of housing.

ACKNOWLEDGEMENTS This project is an outcome of persistent effort while the result of which would have been beyond imagination if not for everyone who has been part of my journey. First and foremost, I am ever grateful to the Supremacy for enabling me to undertake this complex subject. I express my heartfelt gratitude to my family and friends for providing me with the moral and material support. I am honoured to be a part of the institution of Politecnico di Milano, and I earnestly thank my supervising professors for their continued guidance and support throughout the project. I am also thankful to the plethora of research and resources that has been made available as open data, that form the basis of this project. I specially thank Prof. Chella Rajan for sharing some resourceful content from his research team and also Mr. Palanichamy for sharing GIS material. Last but not the least, I am appreciative of the attempts and instances that did not materialise as these experiences enabled me to learn new tools to self develop, and by eventually leading me to paths and people who have today been an active part of my journey in creating this project.

CONTENTS

CONTEXT

9-48 Global Water Crisis Territorial Scale Regional Scale Local Scale Basin Scale

SOLUTION

47-48 Water-Sensitive Urban Design

PRECEDENTS

47 51-68

Principles & Methodologies adopted by Kongjian Yu (Turenscape) Case Studies: Sabarmati Riverfront Development, India Cheonggyecheon Stream Restoration, S.Korea Defensive Strategy: Deltaworks, Netherlands Adaptive Strategy: Room for the River, Netherlands Cascading Semarang, Indonesia Summary

51 57 60 61 62 64 67 71-76

STRATEGY Regional Scale Basin Scale City Scale Building Scale

71 72 73 75 79-108

INTERVENTIONS Regional Scale Basin Scale City Scale Timeline for Implementation ICRERP vs. Amphibious Chennai REFERENCES

9 11 15 18 34

79 85 92 106 107 110

1. GLOBAL WATER CRISIS: Water is a critical natural resource as it is crucial for not just survival of humans, but also necessary for sustaining ecosystems. Water covers 70% of the Earth and is often presumed to be available in abundance. However, freshwater, which is used on a daily basis, is incredibly rare. Only 3% of the world’s water is fresh water, and two-thirds of that is entrapped in frozen glaciers. Currently, the world’s water resources are increasingly under stress threatening ecosystems, economies, and society. According to the World Economic Forum, water crises have been among the top five global risks in each of the last seven years, which is further exacerbated by the global threat of climate change. Research demonstrates that the global demand for water has tripled since the 1950s, while there is decline in the supply of fresh water (Gleick, 2003). About 50,000,000 people live in countries that are water-stressed or water-scarce. By 2025, this number is projected to grow to 3 billion with the increasing population. [1,2]

Oceans 97.5% Freshwater 2.5%

Glaciers 68.7%

Surface & atmosphere 0.4% Wetlands 8.5% Rivers 1.5% Vegetation 1.5%

Permafrost 0.8% Fresh lakes 67.5% Soil moisture 12% Atmosphere 9.5%

Fig.1 Earth’s Water Distribution Source: World bank, raconteur.net

Fig.2 Projected Water Stress across the World by 2040 Source: World Resources Institute (Aqueduct), raconteur.net 9 | Context- Global Water Crisis

Groundwater 30.1%

Asia is home to about 4.5 billion people (approx. 60% of world population), who account for the consumption of around 65% of the world’s water supply. With approximately 30% of the Asian population already facing water scarcity, Asia is one of the regions that is challenged by both- water abundance and scarcity. Two of the largest Asian countries- India and China have witnessed double-digit GDP growth in recent years, coupled with booming population. With the improved socio-economic conditions, the demand for water continues to increase. Many river basins are already unable to cope with the demands of their inhabiting population. [3, 4] The impacts of Climate Change are pertinent with unpredictable and unprecedented seasonal variationsseasons of enormous precipitation followed by drought leading to an unreliable supply of surface water. Most Asian cities witnessing rapid urbanisation while majority are being coastal inhabitations makes them increasingly vulnerable to Sea Level Rise (SLR) associated with Climate Change. Short of steady supply of water through rivers, extraction of ground water is prevalent, further increasing their vulnerability to flooding by the resulting land subsidence. Cities having a high surface water runoff reduces the opportunity natural recharging of aquifers in an effective way. A systemic approach is necessary to tackle these problems to ensuring a steady source of water supply. [5]

Context- Global Water Crisis | 10

2. TERRITORIAL closer Taking a closerSCALE: look Taking at thea Indian look at the Indian context: context: Population Distribution- Fig. 3 shows the Population DistributionFig. country’s 3 shows Approximately 50% of the that approximately 50% of the country’s population lives in areas with an population oflives in areas with Sea an elevation upto 165m Above Mean elevation of upto 165m Above Mean Sea Level (ASL), while 25% of the population Level in (ASL), the population lives areaswhile below25% 60m of ASL. lives in areas below 60m ASL. Coastal metropolitan cities of IndiaCoastal metropolitan of IndiaMumbai, Chennai, andcities Kolkata have Mumbai, Chennai, and Kolkata witnessed rapid urbanization over have the witnessed rapid urbanization over the ……..

years, years, and and the the population of these cities is is projected projected to to increase increase as there is an increasing increasing trend trend of people abandoning their their dependence dependence on primary occupations and and move move to to urban urban areas in search of livelihood. livelihood. [6] [6] This trend trend has has led to urban sprawl, This putting ecological ecological systems systems at risk, and putting the population population vulnerable vulnerable to natural the hazards caused caused by by anthropogenic reasons hazards as the the cities cities grow in an unplanned, as poorly managed managed fashion. fashion. [7, [7, 8, 8, 9] 9] poorly

321m – 8611m ASL 165m – 321m ASL 60m – 165m ASL <60m ASL

Delhi

Kolkata

Mumbai Arabian Sea

Bay of Bengal

Chennai

Indian Ocean

Fig.3 Map showing areas of equal population

Source: GHSL POP (EU-JRC); SRTM (USGS) | Raj Palanichamy 11 | Context- Territorial Scale

Ecological Stress- Fig. 4 shows the ‘baseline water-stress’ in India which is an indicator that measures total annual water withdrawals expressed at a percentage of the total annual available flow. Areas with withdrawals >40% are considered as under High Baseline WaterStress.

Inferences: Along with he Delhi-Mumbai Industrial Corridor, majority of the deccan plateau, and the eastern coast of India is under High Water Stress. Heavy population inhabitation, coupled with the water stress related to mismanagement warns of looming crises. [10, 11, 12]

Delhi

Kolkata

Mumbai Arabian Sea

Bay of Bengal

Chennai

Indian Ocean Extremely High (>80%)

High (40-80%)

Medium-High (20-40%)

Low-Medium (10-20%)

Low (<10%)

Arid & Low Water Use

Fig.4 Map showing areas of baseline water-stress (2020) Source: World Resources Institute Aqueduct

Context- Territorial Scale | 12

Green vs. Grey- Fig. 5 shows an overlay of the major proposed/existing economic corridors of India with the regions of significant tree cover.

Inferences: ……………. The regions along the industrial corridors are seen to be along minimal-no tree cover. This less tree cover extent can be correlated with the development of infrastructure. It can be further noticed that these regions coincide with high baseline water stress.

Amritsar

Delhi

Kolkata

Mumbai Arabian Sea

Bay of Bengal Vizag

Chennai

Kanyakumari Indian Ocean Significant tree cover

Amritsar-Kolkata Industrial Corridor (1839km)

Delhi-Mumbai Industrial Corridor (1504km)

Bengaluru-Mumbai Economic Corridor Chennai-Bengaluru Industrial Corridor

East Coast Economic Corridor

Fig.5 Map showing major proposed/existing economic corridors of India, overlayed with areas of significant tree cover (2010) Source: GLAD UMD 13 | Context- Territorial Scale

Natural HazardFig. 6 shows the ‘Riverine flood risk’ in India which is assessed taking into account the hazard (inundation caused by river overflow), exposure (population in flood zone), and vulnerability. The existing level of flood protection is also considered into the risk calculation. This indicator represents flood risk not …...

Arabian Sea

in terms of maximum possible impact but rather as average annual impact. Inferences: The coastline of India is under risk from riverine flooding. As inferred from the previous maps, heavy population and baseline water stress exacerbate the flood risk in these regions. [13]

Bay of Bengal

Indian Ocean Extremely High

High

Low-Medium

Low

Medium-High

Fig.6 Map showing riverine flood risk (2019) Source: World Resources Institute Aqueduct

Context- Territorial Scale | 14

3. REGIONAL SCALE: Population Densitypopulation density peninsula region.

Fig. 7 shows the in the southern

Inference: In cities like Chennai which is already highly prone to the water-related stresses, looking at the population density, the extent of damage that the city’s inhabitants are prone to can be understood. [7]

Arabian Sea

Bay of Bengal

River basin boundaries Low

Indian Ocean High

Fig.7 Map showing the population density in the deccan plateau (2015) Source: European Commission, JRC; Columbia University, CIESIN

15 | Context- Regional Scale

Ecological Stress- Fig. 8 & 9 demonstrate the reduction in tree cover over a decade, while Fig.10 points the areas of loss in tree cover and deforestation alert........ Inference: Since the coastal areas are already prone show a risk of

riverine flooding, decrease in tree cover means increase in run-off due to decreased infiltration. Vegetation essentially works as a sponge, and forest cover upstream enables in retaining water; loss of tree cover thereby influences peak run-off. [14]

Fig.8 Map showing tree Deccan plateau in 2000

Fig.10 Map showing loss in tree cover 2020

cover

Source: Global Forest Watch

the

Source: Global Forest Watch

Tree cover River basin boundaries Loss in tree cover Deforestation alerts *BoB- Bay of Bengal

Fig.9 Map showing tree cover in 2010 Source: Global Forest Watch

Context- Regional Scale | 16

Green vs. Grey- Fig. 11 shows Chennai city to be devoid of any significant tree cover, whereas the presence of tree cover in the elevated regions outside the Chennai region.

Inference: The highways originating from the green areas outside the Chennai region have the potential to become bio-corridors entering the city.

Fig.11 Map showing the green & grey infrastructure in the vicinity of Chennai region Source: GLAD UMD, ESRI

17 | Context- Regional Scale

4. LOCAL SCALE: Urban Sprawl- Chennai which was founded along the Cooum river has grown rapidly over the years in an unplanned, uncontrolled fashion, indiscriminately encroaching and building upon water bodies within the city, or polluting them and making them an eyesore rather than a resource. Inference: Fig. 12 shows transporta

the

growth

city in a radial fashion along transportation infrastructure. [15] The reinforcement/addition of transportation infrastructure came at an ecological cost of a drastic reduction in the infiltration surface and a decline in the number of surface water bodies. [16] From 1980-1991, the built-up Chennai increased 3 folds.

area

Chennai

Bay of Bengal

1973

1980

1991

2006

Water-bodies

Fig.12 Diachronic map showing the growth of Chennai (1973-2006) Source: Chennai Metropolitan Development Authority

Context- Local Scale | 18

3.50 M (1971)

5.82 M (1991)

Ecological Stress- Fig. 14 shows a series of maps overlaying the urban expansion with the green infrastructure illustrating how the tree cover has declined in <15 years and disappearance of waterbodies in the greater Chennai Metropolitan Area (CMA).

12.58 M (2026- projected)

Fig.13 Population expansion in Chennai

Source: Chennai Metropolitan Development Authority Map A: 1991

Map B: 2006

Map C: 2013

Map D: 2015

Built-up area

Agricultural lands

Tree cover

Fig.14 Maps showing urban sprawl impacting the green infrastructure in Chennai Source: Care Earth Trust

19 | Context- Local Scale

Water-bodies

It has emerged that as the city expanded, >150 water bodies that were part of a flood mitigating system in the city and its suburbs, were encroached and turned into human habitation.

Natural Hazards in the recent past-

The IT boom in Chennai at the turn of the millennium, triggered massive expansion in the south of the city. In 1980, 85% of Chennai was wetlands, while this has declined to 15% by 2016. [16] It is evident what is the kind of impact such a change would have on a river basin.

Fig.16 Photo showing the aftermath of 2004 Tsunami in Chennai Source: Press Trust of India

Tsunami 2004 Losses: 8835 India)

human

lives

(in

mainland

Inundation distance: Upto 1.5km from the coast Cause of disaster: Impact was heightened due to lack of adequate safety measures

Fig.15 Photos showing Pallikaranai marsh Source: R. Padmanaban

encroachment

of Fig.17 Photo showing the aftermath of 2015 Floods in Chennai Source: Press Trust of India

Floods 2015 Losses: >400 human lives Cause: Cloudbursts bringing unprecedented amount of rainfall (1049mm) in ~100 years. The flood was caused and the damage was magnified due to anthropogenic reasons.

Context- Local Scale | 20

2015 Floods causesFollowing an extreme rainfall event, Chennai experienced massive floods in 2015 causing heavy damage to life and economy. Historical return period of the event

Fig.15 Photos showing Pallikaranai marsh

encroachment

Source: R. Padmanaban

Drought 2019 Cause: Low rainfall, water resources

mismanagement

Though Chennai is blessed with ecological resources- 3 rivers running across the city, joining the Bay of Bengal on the east, and multiple wetlands, and urban forests, the city teeters between floods and droughts, and continues to lose out on its water resources due to mismanaged urbanisation and encroachments. With Climate Change and imminent Sea Level Rise, the city needs to adapt, developing its Water Resilience, securing the water needs of the inhabitants while ensuring the ability to resist to natural hazards without letting them become a disaster.

21 | Context- Local Scale

Event/ Station Data

Considering the 2015 event

Without considering the event

Minambakkam

68 years

93 years

IMD 10 x 10 grid point 13.5N 80.5E

86 years

115 years

Large Scale Factors causing the extreme rainfall event: The important large scale characteristics of 2015 are very strong El-Nino phenomenon and very warm BoB, which have the probability of causing this extreme event. The El-Nino of 2015 was one of the strongest reported, which started developing in 2014. The extreme rainfall event was an outcome of a depression generated over a warm Bay of Bengal (BoB) which brought huge moisture from BoB and resulted in heavy precipitation over the South-East coast of India. The Sea Surface Temperature (SST) over BoB has statistically significant increasing trend, attributed to global warming. Small Scale Factors magnifying the extreme rainfall event: Urbanization is another factor which is reported to intensify the extreme precipitation, either through generation of convection due to urban heat island (UHI)- Fig.16 or through the uneven urban terrain resulting in wake diffusion and turbulence. Chennai is reported to have significant urban heat island and there is a possibility of such UHI-extremes link. Though local temperature variations do not have the capacity to organize such a huge extreme events with high moisture flux, but it can increase the intensity of a severe extreme event. [17]

Bay of Bengal

•

reduction in the vent way caused by the construction of bridges,

•

sand bar formation at the mouths of rivers,

•

clogging of the drains due to indiscriminate dumping of solid waste and construction debris,

•

inadequate design capacity

•

lack of connectivity of storm sewers with macro drainage, and

•

encroachments.

Although a road network of about 6000 km exists in the Greater Chennai Corporation, only about 1660 km of storm drains exist. With a rapid increase in the built up area of the city, a major consequence is the reduction in the infiltration component of the hydrologic cycle, which would increase the peak run-off discharge. Another consequence of urbanization is the disappearance of many minor and medium water bodies (Fig.17). These water bodies served as detention basins and resulted in decrease in the peak discharge. Urbanization has reduced the detention effect.

> – 3.65 °C

1.50° to 3.65 °C

-3.65° to - 1.50 °C

3.65° to 7.30 °C

-1.50 ° to 0 °C

7.30° to 11.50 °C

0° to 1.50 °C

Fig.16 Change in LST of Chennai city from 1990 to 2010 Source: USGS, NASA | Raj Palanichamy

Causes for the magnified impact of the extreme rainfall event: There are three major tanks in the Chennai Metropolitan Area (CMA), apart from which existed several other water bodies, the number of which has come down significantly in the last three decades due to urbanization and encroachment of lake beds. The drainage system of Chennai suffers from problems such as:

Inappropriate urbanization may also lead to the encroachment of the waterways, which reduces their vent way. A glaring example of this is the construction of Mass Rapid Transit System (MRTS) along and in some locations in the Buckingham canal. The new runway of the Chennai airport has been built on the Adyar River. [17, 21] Another undermined effect of urbanization is the “compound wall effect”. Compound walls alter the local overland flow paths. This in turn changes the local flooding pattern, protecting some areas while flooding the others. In several cases, the compound wall and roads have affected the natural flow and the lack of

Context- Local Scale | 22

adequate cross drainage has led to much of localized flooding and water logging. Another major factor, though not influential in the 2015 Chennai floods, to be taken into consideration is the ocean tidal levels. Flooding would be exacerbated and recession would be delayed if an intense rainfall event coincides with the occurrence of high tidal levels. [17]

Flooding in various parts of south Chennai as the water that the city received, far exceeded the flood carrying capacity of the Adyar river. All water bodies were completely full from the above-normal November 2015 rainfall and the catchment was completely saturated, resulting in heavy runoff. [17] This clearly signifies the need for resilient river corridors and urban typologies that function as water sponges.

Prevailing extent of surface water (Nov. 2020)

Originally existing water bodies

Fig.17 Existence of surface water bodies Source: Bhuvan WBIS

The city of Chennai has 4 major reservoirs/lakes that cater to majority of Chennai’s water demand: 1.Cholavaram (25M cu.m), 2.Redhills (93M cu.m), 3.Chembarambakkam (103M cu.m), and 4.Poondi (91M cu.m). (Fig.17) These drinking water reservoirs double up as flood control reservoirs in case of emergencies, and the multitude of water bodies should ideally perform the detention function to reduce the peak discharges. When the Chembarambakkam tank is full, excess water is released into the Adyar river (2- Fig.18). Excess water from the Poondi reservoir flows into the Cooum river (1- Fig.18). The release from the Chembarambakkam reservoir caused massive

23 | Context- Local Scale

Fig.18 Maps showing inundation after Dec. 2015 floods Source: IMWI, JAXA

Chennai Droughts causesChennai teeters between floods and droughts as a consequence of its mismanaged urbanization, decreasing the detention as well as the infiltration capacity. Fig. 19 & 20 show some of the many examples where the city has lost its water bodies to urban sprawl.

Fig.19 Map showing a comparison of the waterbodies in a historical map (1814) vs. current satellite image Source: raremaps.com, Google

Thus the ‘blue water’ storage capacity is tremendously impacted- reduced number of surface water bodies, and receding water table levels. (Fig.21) Consequently, when the city receives less rainfall, the impact is imminent, and Chennai faces water shortage. Fig.21 shows the evident fall in water table levels for Chennai over a period of 10 years. Over the years, the regions with deeper water tables has increased excessively.

Fig.20 Map showing a comparison of the waterbodies in a historical map (1814) vs. current satellite image Source: raremaps.com, Google

Context- Local Scale | 24

Climate in ChennaiChennai has tropical climate and the city relies predominantly on the monsoon for the replenishment of its water sources. Scientific theories and model studies (Emanuel, 1987; Knutson and Tuleya, 2004) suggest an increase in tropical cyclones during recent decades. It has been witnessed that the potential destructiveness of cyclones, defined as the total dissipation of power, integrated over the lifetime of the cyclone has increased, is increasing and will increase in a warming environment. [17] 450

400

350

300

250

200

150 100

(mm) the rainfall is With ClimateRainfall change, Average Low Temperature expected to be less distributed across Average high temperature the year, meaning greater peaks resulting

90%

80%

70%

60%

50%

Fig.21 Maps showing a comparison of the groundwater levels of Chennai city in 1991 vs. 2001 Source: rainwaterharvesting.org

40%

30% 20%

10%

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Avg. low temperature °C Avg. high temperature °C Relative Humidity

25 | Context- Local Scale

With Climate change, the rainfall is expected to be less distributed across the year, meaning greater peaks resulting in cloudbursts or extreme rainfall events (example- Chennai rains Nov/Dec 2015), and troughs resulting in dry spells (example- drought 2018/2019).

Sources of Chennai water supplyChennai relies on the following sources to fulfil its water requirements: 1. Surface water sources: lakes, tanks/reservoirs, and rivers of neighbouring states. Water from the tanks (Poondi, Red hills, Cholavaram, Chembarambakkam) are major surface water sources from within Chennai. Additionally, from 2019, the city has expanded its reliance on from new sources- Veeranam lake and quarries of Sikarayapuram and Eraimayur. 2. Ground water: through borewells 3. Sea water desalination plants 4. Tertiary treatment reverse osmosis plants: treats the sewage water generated in the central and western parts of the city. This treated water is supplied to industries.

Fig.22 Maps showing large variations in the reservoirs

seasonal

Source: thenewsminute.com

Context- Local Scale | 26

Chennai Metropolitan Area (1189 Sq.km) Kosasthalaiyar river (90000 c/s) Cholavaram tank

Cooum river (21500 c/s)

~20km

~46km

Redhills tank (Puzhal lake)

Chembarambakkam tank Adyar river (55000 c/s) Chennai city (176 Sq.km) Bay of Bengal

~29km

~12km

Fig.23 Map showing the 3 rivers and reservoirs of Chennai Source: adapted from CMDA

Buckingham canal (48km within CMA)

Kodungaiyur drain (6.9km long) Captain Cotton canal (4km long) Otteri nullah (38.4km long) Virugambakkam-Adambakkam drain (6.9km long) Mambalam drain (9.4km long) Velacheri drain (2.1km long) Veerangal odai (2.8km long) Pallikaranai marsh

Fig.24 Maps showing the macro-drainage network of Chennai Source: adapted from CMDA

27 | Context- Local Scale

Ongoing water-related initiatives-

programmes

and

Among the water-supply/water-saving programmes in Chennai (Fig.25), some of the initiatives are mentioned below: •

Rain Water Harvesting:

Starting from the 1990s, provision of rain water harvesting structures was made obligatory for construction of major developments. Provision of rainwater structures in all types of developments, irrespective of size or use was made mandatory by amending the Building Byelaws in the year 2001. This was applicable for new constructions as well as existing buildings. In 2001, it was mandated that all centrally air-conditioned buildings shall

have their own wastewater reclamation plants and shall use reclaimed wastewater for cooling purposes. •

Check dams & Injection wells:

In order to keep the sustainable yield of the aquifers and to arrest sea water intrusion long term measures such as (i) construction of check-dams across River Kosasthalaiyar and (ii) construction of Injection wells in Minjur Aquifer have been initiated. Construction of check dams was implemented in order to harness the flood waters available during the monsoon periods to recharge the ground water. To arrest sea water intrusion in a coastal aquifer, 15 injection wells of 350mm dia. and 45m depth were constructed to create an artificial barrier of fresh water. [18]

Fig.25 Map showing the water supply system of Chennai Source: CMWSSB

Context- Local Scale | 28

•

Integrated Cooum River Eco Restoration Plan (ICRERP):

The Integrated Cooum River EcoRestoration Plan proposes to tackle the restoration/rejuvenation of the Cooum river from Paruthipattu (as pollution sources are predominant downstream of Paruthipattu), in the densely populated urban area. Some of the objectives of ICRERP are:

Waste management: To collect the floating debris on the river surface, boom systems are proposed to be installed in 10 points along the river. In areas where the existing network does not have enough capacity to handle the sewage, in situ treatment is proposed. For this purpose six modular sewage treatment plants are proposed.

- Pollution abatement. - Maintaining minimum ecological flows in the river - Improving and maintaining the floodcarrying capacity of the river. - Riverfront development within urbanised areas, wherever possible. Proposal: Fluvial corridor: Only river channel improvement solutions are proposed by the plan. As shown in Fig.26, these are categorized into 3 segments: 1. From Paruthippatu to Virugambakkam 2. From Virugambakkam to Aminjikari 3. From Aminjikari to mouth (zone of tidal influence)

river

Fig.27 Photo showing boom barriers to entrap floating debris Source: tuffboom.com

Social Assessment: 14,257 families will be affected by the restoration project. 76 slums have been identified along the banks of the Cooum river that will be resettled. [19]

Fig.26 Extent of the Integrated Cooum River Eco-Restoration Plan Data Source: Executive Summary- ICRERP

29 | Context- Local Scale

Context- Local Scale | 30

Virugambakkam-Aminjikarai

Source: Executive Summary- ICRERP

Fig.28 Map showing areas of intervention of the ICRERP

Paruthipatti-Virugambakkam

Aminjikarai-Mouth of river

Segment 1: Paruthippatu to Virugambakkam

Proposed STPs Chennai City extent

Flood control strategy: In this stretch of the river which lies within the CMA (outside the city limit), the ICRERP proposes the regularization of the riverbed’s slope and creation of a 3m wide canal (Fig.29).

Encroachments to be resettled New residential zones to be developed Slums to be developed in-situ Mangrove plantation

The main function of the canal is to convey water during low flow season and avoid stagnation along the river.

Existing canals draining into Cooum river

Biodiversity: Due to the highly polluted state of the soil along the banks, plant species of commercial value- timber yielding terrestrial tree species are proposed be planted in this stretch. [19]

Canal draining off the seasonal low flow

Timber-yielding tree species

Flooded extent of river during extreme events

Drainage interceptors

Fig.29 Interventions in segment 1 of ICRERP implementation extent Source: adapted from Executive Summary ICRERP

31 | Context- Local Scale

Segment 2: Virugambakkam to Aminjikarai

Flood control strategy: The Virugambakkam to Aminjikarai stretch starts from within the CMA and transitions to within the city limits in Aminjikarai. Regularization of the riverbed’s slope

Canal draining off the seasonal low flow

and creation of a 8m wide canal is proposed by the ICRERP for this stretch (Fig.30). Biodiversity: Flora species of commercial value- timber yielding terrestrial trees are proposed be planted in this stretch. [19]

Timber-yielding tree species

Flooded extent of river during extreme events

Drainage interceptors

Fig.30 Interventions in segment 2 of ICRERP implementation extent Source: adapted from Executive Summary ICRERP

Context- Local Scale | 32

Segment

Aminjikarai

river

mouth

Flood control strategy: The last stretch of the Cooum river from Aminjikarai to the river mouth, lies well within the city limits, majority of which falls within an area of tidal influence. The ICRERP, for this stretch, proposes regularization of the riverbed’s slope and deepening of the riverbed. creation of a 8m wide canal is proposed by the ICRERP for this stretch (Fig.31).

Tree species of commercial value

Drainage interceptors

Biodiversity: Closer to the mouth of the river, from Chetpet, which is the area of tidal influence, Mangrove plantations are proposed for their ability to withstand salinity, wave action and possibility to grow in poor soils, preventing ground water pollution . Flora species of commercial value- timber yielding terrestrial trees are proposed be planted in this stretch. [19]

Mangrove tree species In areas of tidal influence

Slums to be rehabilitated

Fig.31 Interventions in segment 3 of ICRERP implementation extent Source: adapted from Executive Summary ICRERP

33 | Context- Local Scale

Flooded extent of river during extreme events

4. BASIN SCALE:

Present state:

The Cooum river and its basin- Cooum is a seasonal river in a heavily polluted state which drains into the Bay of Bengal river on the east coast. The river is about 72km long, originating in the Thiruvallur district, upstream of Chennai.

Fluvial Corridor: The Cooum is a shallow and wide river in the peri urban zone of Chennai, transitioning into a narrow, deep and wall protected channel in some parts within the city limits of Chennai.

On basis of the simulated annual water balance for the base year 2020, the Cooum basin is water deficit by 74% (Fig.32).

Water demand

From Paruthipattu to the city limit, several contractions impact the flood carrying capacity of the river. Transverse structures (causeways- Fig.34) and encroachments reduce the hydraulic capacity of the river leading to a backwater effect.

Water sources potential

Fig.32 Simulated annal water balance in the Cooum river basin (2020) Source: Study of Chennai River Basin- PWD 2007

Over 20% of the water demand irrigational purposes (Fig.33).

for

Fig.34 Photo of a causeway obstructing flow of the Cooum river Source: The Hindu, M. Vedhan

Water Quality: Upstream, the flow in the river is seasonal, whereas, within the city limits the water quality drastically changes, transparency is lost, colour changes and morbidly reeks of sewage. Sewage outfalls in the river consisting of domestic and industrial waste, along with solid waste dumped into the river. Soil Quality: The soil is found in a degraded state, but not categorized as ‘hazardous’ as per local parameters. [19]

Industries

Irrigation

Livestock

Others

Fig.33 Water river basin

consumption

Domestic

the

Cooum

Source: Study of Chennai River Basin- PWD 2007

Encroachments: They are identifiable along the entire river corridor though more prominent within the metropolitan area. Outside the CMA, encroachments are more inconspicuous, for instance, in the form of agricultural fields in the fluvial corridor, or landfills in the floodplain (Fig.42).

Context- Local Scale | 34

Watershed delineation-

Present state:

Using GIS, the Cooum basin extent and the hydrologic pattern of the basin was delineated (Fig.35) from Digital Elevation Model (DEM) of 30m spatial resolution.

Overlaying the delineated watershed with the satellite image of the city (Fig.36), it is evident how the urban typologies and planning have very little correlation with the hydrologic pattern of the basin.

From Paruthipattu to the city limit, several contractions impact the flood carrying capacity of the river. Transverse structures (causeways- Fig.34) and encroachments reduce Fig.36 Map showing infrastructure cutting across natural inundation areas the hydraulic capacity of the leading to a backwater effect.

Fig.35 Map showing the delineated Cooum watershed and its hydrological pattern

35 | Context- Local Scale

river

Cooum river environsCooum river is about 72 km long, flowing eastward towards the Bay of Bengal. 1.At the origin: The Cooum river branches out from the Kosasthalaiyar river, at the bifurcation of which is located the Kesavaram Anicut/Dam (Fig.37 & Fig.38).

Correlating this with the increase in the number of farmers abandoning agriculture due to lack of water, it is evident that the agricultural practices involve cultivation of water-intensive crops. The upstream area of the Cooum basin, outside Chennai, is predominantly crop fields with agricultural tanks/retention ponds/lakes (Fig.39 & Fig.41). The overflow of these water bodies form a stream that joins the Cooum river 10km downstream of its origin, near Satharai village.

Fig.37 Kesavaram dam across Cooum river Source: Google Maps contributor DJ Tamil

Fig.38 river

Check

dam

across

Kosathalaiyar

Source: Google Maps contributor Ram Mohan

This dam which was built along with the Poondi reservoir (a major source of water supply to Chennai), diverts the water to the bifurcated arm of the Kosasthalaiyar river (Fig.40), directing the water to the Poondi reservoir. Therefore, barring periods of heavy rain spells, the water from the parent river doesn’t enter the Cooum river at its origin. Inferring from the simulated annual water balance of the Cooum river (Fig.33), over 20% of the water demand is consumed for irrigational use.

2.In the Metropolitan Area: Mid-course of the river, around 27km downstream its origin, the Cooum river enter the Chennai Metropolitan Area (CMA). There is increase in the density of the settlements and a decrease in the extent of crop fields with incidences of fallow/barren land. This land surrounding water bodies is prone to inhabitation, and consequently, the water body is prone to pollution or eventual disappearance, similar to the other surface water bodies that once existed in Chennai. Lakes Y (Kolathur lake) and Z (Retteri lake) may have been a single water body in the past stretching across 4km, now encroached upon (Fig.43 & Fig.44). The increase in the settlement areas marks the start of the sewage outfalls in the river, and landfills in flood plains.

Fig.42 Landfill in the floodplain Source: Google Earth

Context- Local Scale | 36

Cooum watershed

Agricultural reservoirs

Canals

Tree cover/ plantations

Fig.39 Map showing the Cooum river basin at its origin

Kesavaram dam: Located at the origin of Cooum river diverting water away from it Kosasthalaiyar river: Branching out as Cooum river

Fig.40 Section A (~60m ASL)

37 | Context- Local Scale

Water diverted to Poondi reservoir through the Kosasthalaiyar river

Agricultural fields with water-intensive crops

Low density developments

Tree cover prone to felling

Absence of any significant tree cover

Non-perennial Cooum river; Seasonal waterflow diverted to Kosasthalaiyar river upstream

Fig.41 Section B

Cooum watershed

Slums along the river

Railway line

New residential zones allotted

Extent of CMA

Lakes/areas of inundation

Drainage channels

Tree cover

Medium density developments

Fig.43 Map showing the Cooum river basin in the CMA

Context- Local Scale | 38

Flood plain undergoing encroachment

Medium/low density settlements prone to grow Flood plain prone to risk of encroachment

Barren land surrounding waterbody prone to inhabitation

Waterbodies vulnerable to encroachment

Fragmented settlements

Start of sewage outfalls into the Cooum river River undergoing pollution

Disappearing tree cover Agricultural fields with water-intensive crops

Disappearing tree cover

Fig.44 Section C (~30m ASL) 3.Within the city: About 47km downstream its origin, the Cooum river enters Chennai city where there are extremely dense settlements. The river course becomes highly constricted, in some parts as a narrow, deep and wall protected channel (Fig.45).

Slums and other encroachments dominate the riverfront which also discharge their refuse directly into the river (Fig.46). About 118 outfalls are reported in the Cooum river, out of which 106 are just within the city limits. [19] Within the city limits, the water quality drastically changes; transparency is lost, colour changes and morbidly reeks of sewage. With a disparity between the demand and supply of water in Chennai, there is dependence on groundwater to supplement the city’s water requirement. In addition to receding water tables, closer to the coastline, groundwater extraction has resulted in saltwater intrusion. With the global climate change, sea level rise is another major threat to Chennai. [20]

Fig.45 Photo showing a constricted and heavily polluted section of Cooum river Source: veethi.com

The high density urban fabric, coupled with minimal tree cover has resulted in sealed surfaces, consequently making the infiltration negligible. Sewage outfalls in the river consisting of domestic and industrial waste, along with solid waste dumped into the river, reduce the river into an open sewer.

39 | Context- Local Scale

Fig.46 Clearing of encroachments Source: Theo Whitcomb

High density developments

Chennai city extent

Drainage channels

Slums along the river corridor

Fig.47 Map showing the Cooum river basin within the city Informal settlements Constricted river course

Highly dense urban fabric + Heavy run-off

Disappearing Water bodies Disappearing tree cover

Fig.48 Section D (~15m ASL) Heavily polluted river course Poorly planned infrastructure

Ground-water extraction + Saltwater intrusion

Island prone to inundation

Threat of sea level rise

Fig.49 Section E (~5m ASL)

Context- Local Scale | 40

Various edge conditions of river within the city extent:

the

Cooum

ImpermeabilityHeavy runoff + Flooding

Fig.51 Scenario 1- Key plan

3.Within the city: About 47km downstream its origin, the Cooum river enters Chennai city where there are extremely dense settlements. The river course Pollutionbecomes highly constricted, in some parts Solid waste + Sewage as a narrow, deep and wall protected channel (Fig.45).

Fig.52 Photo showing the river condition near Nungambakkam bridge Inaccessibility + Encroachments

The high density urban fabric, coupled with minimal tree +cover has resulted in Groundwater extraction Receding water table +consequently making the sealed surfaces, Saltwater intrusion infiltration negligible. Sewage outfalls in the river consisting of domestic and Fig.50 Diagrams the industrial waste,enumerating along with some solidofwaste problems in the Cooum river-basin dumped into the river, reduce the river into an open sewer.

41 | Context- Local Scale

edge

Source: Google contributor

Fig.53 Photo showing the river edge condition near Nungambakkam bridge (looking upstream) Source: Google contributor

Fig.54 Section through the Cooum river near the Nungambakkam railway bridge (looking upstream)- Scenario 1

Encroachments Debris

Fig.55 Scenario 2- Key plan

Fig.56 Photo of a walled portion of the Cooum river near Chetpet Source: Google contributor

Fig.57 Photo of a walled portion of the Cooum river near Chetpet Source: Google contributor

Context- Local Scale | 42

Fig.58 Section through a walled portion of the Cooum river near Chetpet (looking upstream)- Scenario 2

Offices/commercial establishments Nungambakkam bridge (located downstream)

Fig.59 Scenario 3- Key plan

Fig.60 Photo near Chetpet showing construction of the elevated expressway within the Cooum fluvial corridor Source: andamansaravanan.blogspot.com

Fig.61 Photo near Chetpet showing construction of the elevated expressway within the Cooum fluvial corridor Source: andamansaravanan.blogspot.com

43 | Context- Local Scale

Elevated expressway on the fluvial corridor

Fig.62 Section through the Cooum river near Chetpet showing the elevated expressway (looking downstream)Scenario 3

Encroachments

Fig.63 Scenario 4- Key plan

Fig.64 Photo showing low income housing along the Cooum river near Chindadripet Source: Google contributor

Context- Local Scale | 44

45 | Context- Local Scale

Fig.65 Section through the Cooum river near Chindadripet (looking downstream)- Scenario 4

Transportation infrastructure along fluvial corridor

Slums/low income housing in dilapidated condition

Concluding from the context, it is evident that Chennai is unequipped to confront the periodic water stresses and the unprecedented shocks from extreme rainfall or cloudbursts which are imminent with Climate Change. The city faces multiple water-related risks — from flooding to sea level rise to receding water table levels, and yet, the urban typologies and city planning are indifferent to the region’s ecological realities and challenges. To reduce the impact of these events, traditional approaches to rainwater management are not only an economic liability but are also inadequate, owing to their inability to evolve with the changing climate.

Natural ground cover 40% evapotranspiration

10% run-off

25% deep infiltration 25% shallow infiltration

10-20% impervious surfaces 38% evapotranspiration

Currently, the world’s water resources are increasingly under stressthreatening ecosystems, economies, and society. This calls for a holistic approach, cashing in on the intrinsic ability of green infrastructure to perform as “water sponges” and to transform cities as “sponge cities”. [22] ‘Sponge cities’ offer a wide benefits:

range of

1. Improved water quantity and quality 2. Reduction in flood risk 3. Decreased dependence on engineered systems and grey infrastructure 4. Improved public realm [23] Integrating infrastructure:

green

with

The multiple benefits of green infrastructure with systems include-

20% run-off

21% deep infiltration 21% shallow infiltration 75-100% impervious surfaces 30% evapotranspiration

grey

55% run-off

integrating engineered

1. Technical and environmental benefits: Green infrastructure can boost infrastructure system resilience due to its natural adaptive and regenerative capacity.

47 | Solution- Water Sensitive Urban Design

5% deep infiltration 10% shallow infiltration

Fig.66 Relationship between the surface runoff, infiltration and nature of the ground surface

2. Social: Green infrastructure empowers communities through participation in project operations. This enhances project sustainability as long-term viability is highly dependent on community support. 3. Green infrastructure can be low-cost, and cost-effective, helping enhance the economic efficiency of infrastructure investments. Its multiple benefits can generate both monetary values and nonmarket benefits. Numerous studies and scenarios demonstrate how nature’s innate ability can be harnessed to substitute for or enhance infrastructure systems, and design development projects in ways that both address development challenges and curb ecosystem degradation. These types of strategies are collectively called nature-based solutions, while solutions explicitly designed to deliver a service are termed “green infrastructure”. [24]

Green:

Grey:

Green with grey:

Fig.68 Advantages of integrating green infrastructural components with grey infrastructure

Source: Integrating the grey, green and blueYaella et. al

Green roof

Green walls & street trees

Bioswale

Rain-garden

Fig.67 Examples of green infrastructure components Source: ontheplatform.ork.uk

Water Sensitive Urban Design | 48

Deep form vs. shallow formAs explained by John T. Lyle, a “deep form” is shaped by the interactions of inner ecological process and human vision (Fig.69) which can make the underlying order visible and meaningful in human terms. Contrasting to this is the “shallow from”, which only has the surface perceptual order and lacks the solidity of coherent process beneath the surface (Fig.70). In deep form is a meeting of appearance and reality, mind and nature, art and science.

To generate a deep form requires rational understanding of natural systems in combination with intuitive imagery, and thus a design process that combines high levels of both analytical and creative thinking. The Author proposes we take the underlying complex and elegant ecosystematic order of nature as the essential and fundamental inspiration for design. [25] In correlation with this, Landscape Architect Kongjian Yu of Turenscape recommends 2 levels of actions to create “deep forms”: 1. Planning to create configurative deep forms, 2. Designing to deep forms

create

transformative

Principles and Methodologies adopted by Kongjiyan Yu-

Fig.69 Example of “deep form” at small scale Source: treehugger.com

To design to create transformative “deep forms”, some of the principles implemented by the Landscape Architect in his projects are: - Accepting & living with the floods - Using the landscape productively - Value the ordinary- Reuse & Recycle - Minimize intervention - Porous landscape: pond-dyke model - Let nature do the work (remediation) - Designed ecologies for water cleansing; using abstracted terraces - Green solutions for recovering mother rivers

Fig.70 Example of “shallow form” at small scale Source: readersdigest.ca

51 | Precedents- Principle & Methodologies

- Small solutions impacts [26]

cumulative

for

big

1. Living with the floodsTHE FLOATING GARDENS (21.3 Ha)

vegetation, but also to promote continuity of the design with the surrounding ecosystem.

An ecological approach for the stormwater management is proposed as an alternative to the engineered, grey infrastructure approach. It provides an alternative flood control and storm water management solution to be used as a model for the entire river valley.

Fig.73 Layers of the natural matrix Source: turenscape.com

The upper layer for humans which "floats" above the seasonally flooded natural matrix, is composed of groves of native trees, a network of paths extends from the urban fabric downwards the park.

10 year flood

50 year flood

20 year flood

Location of the park

Fig.71 Flooding extent along the Yongning river Source: turenscape.com

Fig.72 Bank of the river- Before & After Source: turenscape.com

The park situated along the Yongning river is composed of two layers: the natural matrix overlapped with the human matrix-the floating gardens. The natural matrix is composed of wetland and natural vegetation designed for the natural processes of flooding and native habitats. Above this natural matrix, float the gardens of humanity composed of a designed tree matrix, a path network, and a matrix of story boxes. Native wetland plants, trees and bamboos are massed along the riverbank and throughout the design not only to ensure successful establishment of the

Fig.74 Layers of the human matrix Source: turenscape.com

Fig.75 Overall floating gardens

masterplan

the

Source: turenscape.com

Precedents- Principles & Methodologies | 52

2. Productive use of landscapeSHENYANG ARCHITECTURAL UNIVERSITY (21 Ha)

vegetation, but also to promote continuity of the design with the surrounding ecosystem.

Fig.78 A view of the rice fields Source: turenscape.com

1- Central pond 2- Dry crop area

3- Rice fields 4- Library

Fig.76 Masterplan of the University Source: turenscape.com

The upper layer for humans which "floats" above the seasonally flooded natural matrix, is composed of groves of native trees, a network of paths extends from the urban fabric downwards the park.

China’s rapid urbanisation is inevitably encroaching upon limited arable terrain, raising issues of sustainable land use. With 20% of the world population and only 18% of cultivable land, China is in the danger of squandering one of its most important and limited resource. The project demonstrates how agricultural landscape can become a part of the urbanized environment and create a cultural identity. This concept is implemented in the design by the use of rice, native plants and crops to keep the landscape productive (Fig.76,78,79) while fulfilling its new role as an environment for learning.

Fig.77 Spaces alongside cultivated land Source: turenscape.com

53 | Precedents- Principles & Methodologies

Fig.79 A view of the dry crop area Source: turenscape.com

3. Porous landscape: Pond-dyke modelQUNLI STORMWATER PARK (34.2 Ha)

Skywalk, pavilion & towers

Ground level path network & platform

Fig.80 Masterplan of the stormwater park Source: turenscape.com

In 2006, a new urban district, Qunli New Town (2733 Hectares), was planned to be developed at the east outskirt of Haerbin City of North China, a region where flooding and water-logging were seen often. While only about 16.4% of the developable land was zoned as permeable green space, the majority of the former flat plain will be covered with impermeable concrete. The site to be developed as a park, was a former wetland, that was later surrounded by roads and dense development on all sides. The design solution was the use of simple cut-and-fill technique to create a necklace of ponds-and-mounds surrounding the former wetland, while leaving a major core of the wetland untouched and left alone for natural evolution and transformation (Fig.81). The pond-andmound ring surrounding the periphery of the wetland creates a storm water filtrating and cleansing buffer zone for the core wetland, and a welcoming landscape filter between nature and city. Native wetland grasses and meadow are grown in the ponds of various depths and the natural evolution process is initiated. Through the transformation of this dying wetland, showcasing an approach of watersensitive urbanism, stormwater that frequently causes flood in the city become a positive environmental amenity for the city.

Fill ring (mounds)

Cut ring (ponds)

Existing wetland

Fig.81 Layers of the stormwater park Source: turenscape.com

Fig.82 An aerial view of the park Source: turenscape.com

Precedents- Principles & Methodologies | 54

4. Designed ecologies for water cleansingLIUPANSHUI MINGHU WETLAND PARK (60 Ha)

The strategy implemented is to slow the flow of water from the hillside slopes and create a water-based ecological infrastructure that will retain and remediate the stormwater (Fig.85), and make water the active agent in the regeneration of a healthy ecosystem that will provide natural and cultural services in order to transform the industrial city into a liveable habitat.

Fig.83 Masterplan of the wetland park Source: turenscape.com

The holistic strategy for the project targets to address some serious problems: - Water pollution: Situated along with one of the major heavy industrial cities. From its industrial chimneys, decades of air pollution deposits have fallen onto the surrounding slopes and been washed into the river along with stormwater runoff that carries chemical fertiliser runoff from the farm land on the slopes and sewage from the scattered settlements in the area

Fig.85 Concept of the wetland park Source: landscapeperformance.org

- Flood and stormwater inundation - Channelization of the main river - Lack of public space (Fig.84) Fig.86 Terraced bioswales- water filters Source: turenscape.com

Fig.84 Before and after the intervention Source: turenscape.com

55 | Precedents- Principles & Methodologies

Fig.87 Levels of the wetland park Source: turenscape.com

5. Recovering mother riversSANLIHE GREENWAY

6. Small impacts-

solutions

cumulative

for

big

Industry Transport Commercial & public Households Agriculture, forestry & fishing Other

Fig.88 Dechannelizing the river- Step 1 Source: turenscape.com

Fig.92 Energy consumption by sector Source: Eurostat

With buildings being the major source of energy consumption (Fig.92), small scale interventions at the building level will cumulatively bring about a major impact. Fig.89 Recovering the natural hydrological pattern- Step 2

Fig.90 Wetlands at nodes for cleansingStep 3

Treated greywater to kitchen

Fig.91 Adding ponds further increasing the “sponges”- Step 4

Nutrient-rich water

Rainwater

Urine collection

Treated greywater

Fig.93 An example of energy/water management at the building scale Source: re-thinkingthefuture.com, biome-solutions.com

Fig.94 system

natural

greywater

filtrating

Source: colourbox.com

Precedents- Principles & Methodologies | 56

SABARMATI RIVERFRONT Ahmedabad, India

DEVELOPMENT,

The Sabarmati river which was once a source of drinking water and informal recreational activities for Ahmedabad, with rapid and haphazard urbanization became neglected, inaccessible and polluted. Over time, as the city grew, the natural course of the river was encroached upon. Unrestricted flow of industrial and domestic waste polluted the river. Informal settlements sprung up along the river added to the problem and these settlements were prone to flooding during the monsoon.

Fig.95 Formerly inaccessible riverfront Source: smartnet.niua.org

1. Enabling public accessibility- A twolevel, continuous promenade at the water’s edge along each bank of the river is enabled by opting for changes to the river profile through channelization. (Fig.97)

Fig.97 Areas to be reclaimed along the Sabarmati river Source: smartnet.niua.org

Fig.91 Adding ponds further increasing the “sponges”- Step 4 Fig.96 Accessible riverfront (after) Source: smartnet.niua.org

Objectives of the Sabarmati Development Project:

Riverfront

- Enabling public accessibility - Keeping the river pollution-free - Reducing risk of erosion and flooding - Rehabilitating slum dwellers - Providing public spaces and sociocultural amenities - Rejuvenating riverfront neighbourhoods - Generating a self-finance model - Giving the city a memorable identity

57 | Precedents- Sabarmati Riverfront Development

Fig.97 Enabling public accessibility by channelizing the Sabarmati river withing Ahmedabad- an engineered approach

Source: smartnet.niua.org

The area reclaimed along both banks comprise of parks and green spaces constituting about 50% of the land reclaimed to facilitate the riverfront access (Fig.98).

Fig.100 Routing the interceptor sewage lines to sewage treatment plants Source: smartnet.niua.org

275m

The river has been channelized to a constant width to maintain the flood carrying capacity uninterrupted, to provide protection from periodic flooding and prevent erosion of the river banks. 3. Providing public spaces and sociocultural amenitiesThe formerly unorganized activities happening along the river, such as the ‘Sunday market’ and ‘dhobhi ghats’ are accommodated in formal facilities (Fig. 101). Riverfront Market

Fig.98 Areas reclaimed along the river

Exhibition Centre

Laundry Campus

Source: smartnet.niua.org

2. Keeping the river pollution free and reducing the risk of flood/erosion- To stop untreated sewage from flowing into the river, the riverfront development includes two interceptor sewer lines on both banks of the river (Fig.99, 100), capturing 38 sewage discharge points and routing sewage with new pumping stations in the reclaimed banks.

Events Ground

Fig.101 Amenities along the riverfront Source: smartnet.niua.org

The historic Sunday market, has been refurbished as Riverfront Market adjacent to its previous location (Fig.102). A laundry campus has been created to provide facilities for the washing community that used the river banks for laundering (Fig.103).

Fig.99 Intercepting sewage outfalls Source: smartnet.niua.org

These lines carry untreated sewage to the two recently augmented sewage treatment plants (Fig.100). The treated water from these plants will be used in the future to replenish the river.

Fig.102 An impression of the market Source: smartnet.niua.org

Precedents- Sabarmati Riverfront Development | 58

5. A self-financing model for the riverfront development- to achieve its objectives without relying on any government funding, a small portion of the reclaimed land is sold for commercial development to generate adequate resources to pay for developing the riverfront and managing it (Fig.106).

Fig.103 A formal laundry campus Source: smartnet.niua.org

Trade-fair facilities for the business community are integrated with outdoor vending areas, situated all along the length of the project accommodating informal vendors. 4. Rejuvenation of the riverfront neighbourhoods18 precincts are identified which will undergo gradual ‘upgradation’ promoting integrated and high-density growth (Fig.104).

Fig.104 18 precincts for rejuvenation Source: smartnet.niua.org

Fig.105 Precinct 5- existing vs. proposed

Source: smartnet.niua.org

59 | Precedents- Sabarmati Riverfront Development

Fig.106 Saleable land along the river Source: smartnet.niua.org

The project still under realisation has already led to increased land values, thus reducing the percentage of land for sale from that originally thought necessary. The private developments that will be built on the riverfront will be subjected controlled by volumetric regulations to ensure that the built environment along the riverfront is harmonious and has a memorable skyline. [27, 28]

CHEONGGYECHEON STREAM RESTORATION, Seoul, South Korea The Cheonggyecheon stream, a channel that joins the Han river, runs through the downtown area of the densely populated Seoul. Following rapid urbanization, the stream was completely covered with a roadway. Additionally, another elevated highway was added over the roadway, burying the stream out of sight.

is reserved for biodiversity with limited human interference (Fig.108, 109). UPSTREAM:HISTORY

CULTURE

NATURE

Fig.108 Zoning of the restored stream Source: seouldsolution.kr

Over the years, Cheonggyecheon area had become a shabby industrial area, suffered from chronic, massive traffic volumes with high levels of congestion, pollution and elevated temperatures (urban heat island). The roadways exhibited structural disintegration. Considering the above factors, the highway was proposed to be removed (Fig.107), and the stream to be restored.

Fig.109 Stream scenarios: zone 1, 2 & 3 Source: urban-regeneration.worldbank.org

The source of water entering the stream is majorly water pumped from the Han river, and also the water from the subway stations. To maintain the water quality of the stream, and to overcome the heavy levels of contamination that is typically constituent in the initial discharge stormwater, a double canal/sewage system is adopted to suffice even during extreme rainfall events (Fig.110). Fig.107 Dismantling of the roadways Source: seoulsolution.kr

The priority of the restoration project was flood control. The intervention leans more towards the urban/engineered approach: the stream was opted to be channelised to secure a flood carrying capacity of 200 years. The up-stream area of the restored park is dotted with public spaces while the down-stream area

Fig.110 Measures to regulate the water quality entering the stream Source: Seoul Metropolitan Government

Precedents- Cheonggyecheon Stream Restoration | 60

DEFENSIVE Netherlands

Outcome of the restoration project: - Increased in number of pedestrian visitors

STRATEGY:

DELTAWORKS,

- Reduction in land surface temperatures

The Deltaworks is the largest engineered flood protection system, comprising of dams, storm barriers, dykes and levees. In the densely populated areas near the river mouths of the Rhine, the Meuse, and the Schelde, it proved very difficult to build new dikes or strengthen the original ones. The solution resolved was to close all the river mouths, the ‘Deltaplan’. By doing so, 700km of dyke length would be reduced.

- Corridor for wind passage created

The necessity:

- Increased biodiversity with greater number of bird, fish and insect species

With around 17% of the country’s current land area claimed from the sea or lakes, about 26% of the country’s area below sea level (Fig.112), 21% of population living in areas below sea level, 66% of the country is vulnerable to submergence in the absence of any protective measures.

- Reduction in use of private vehicles entering the Cheonggyecheon area, increase in use of public transportation - Improved air and water quality - Reduction in noise level

- Increase in price of land by 30-50% for properties within 50m of the restored area. This is double the rate of property increases in other areas of Seoul. [29, 30]

Fig.111 Surface temperature Cheonggyecheon (post-restoration) nearby street

of vs.

Source: seoulsolution.kr

N.A.P. is the Amsterdam Ordnance Level which is the reference plane for sea level height in the Netherlands.

Fig.112 Map showing areas of Netherlands

the

flood

prone

Source: Research Publication- Haasnoot Et. al

Posing this threat to the country are the North Sea, the Rhine (Waal) river and the Meuse river, Ysselmeer lake. The flood of 1953 which claimed the life of 1835 people and hundreds of animals, while

61 | Precedents- Deltaworks

submerging 150,000 hectares of land under sea water, triggered the urgent action plan to implement the Deltaworks project, an engineered approach to better protect the Netherlands against water.

ADAPTIVE STRATEGY: ROOM FOR THE RIVER, Netherlands This initiative seeks to restore natural “sponges” of water such as marshes and wetlands to increase the flood water storage capacity. Inherently, these also improve the biodiversity of rivers, while enhancing their aesthetic and recreational value. Formerly, in the Netherlands, water management was seen as a matter of civil engineering and the interventions aimed at controlling nature. Over the last centuries, this approach has resulted in gradual development in the floodplain of rivers thereby reduced room for the rivers, requiring repeated heightening of flood defences. An approach transitioning from ‘fighting with water’ to ‘living with water’ was necessary. [33]

Fig.113 Map showing proposed levels of protection against flooding

Lowering of floodplains

Deepening of summer bed

Dyke relocation

Water storage

Depoldering

Dyke strengthening

Lowering groynes

High-water channel

Removing obstacles

Source: Research Publication- Van Alphen

Presently, flood protection in Netherlands is delivered by a system of 3700 km primary flood defences, (dikes, dunes, sea walls, dams and storm surge barriers), which prevent flooding from the North Sea and major rivers and lakes. In addition, a system of 14,000 km of secondary dikes prevents flooding due to the regional water systems.

Fig.114 Measures of Room for the River Source: rijkswaterstaat.nl

This flood protection system also requires dealing with a sea level rise of about 2 mm/y, and already existing saline seepage of brackish groundwater, salt intrusion in the estuaries and land subsidence. The new flood protection standards are achieved combined with adaptive strategies such as the so-called ‘Room for the Rivers’ that include floodplain and side channel excavations, backward dike realignment and flood retention that reduce extreme flood levels. [31, 32] Fig.115 Map showing intervention areas Source: IHE

Precedents- Room for the River | 62

DYKE RELOCATION (Room for Waal river), Nijmegen, Netherlands Located upstream of the Waal river (Fig.116) in Nijmegen, this is the most complex project within the Room for the River programme. By constructing a bypass channel, an elongated island is created in the river Waal (Fig.117), between the historic centre and the north shore of the Waal River.

The island and bypass channel together form a river park that while reducing the flood risks, also offers recreational, ecological and aesthetic values (Fig.118). The design objective was to experience the river landscape and incorporate the river dynamics (Fig.119). For example, some paths will occasionally be flooded in the event of high water levels, only being accessible via stepping stones. Resultantly, a recreational, urban river park is created, with part of the new island available for housing. High water levels are reduced by 34cm. [34, 35]

Fig.116 Map intervention Fig.117 Map created as a

showing the location of the upstream of the Waal river showing the elongated island result of dyke relocation

1day/year

5days/year

50days/year

180days/year

Source: H+N+S Landscape Architects

Fig.119 Dynamic nature of the river Source: H+N+S Architects

Fig.118 Masterplan

Source: H+N+S Landscape Architects

Relocated dyke

Previous location of dyke

Fig.119 Revised dyke location Source: ruimtevoorderivier

63 | Precedents- Room for the River

Fig.120 Before and after dyke relocation Source: Landezine, Johan Roerink Aeropicture

CASCADING SEMARANG, Semarang, Indonesia Semarang with the 5th largest metropolitan area in Indonesia is the capital of Central Java province. Mount Ungaran located 20 km south of Semarang is part of the Javan volcanic mountain range, highly prone to earthquakes (Fig.121). This mountain adds to a strong topography around Semarang with a strong slope from the hilly inland to the coastal lowlands.

rise, this flooding and damages expected to increase in Semarang.

are

The city is slowly growing into the hilly regions, occupying more territory, with increased landslide risks due to higher degrees of deforestation and surface sealing. Additionally, this expansion also impacts recharge of different aquifer levels beneath the city (Fig.122).

1 2

Fig.122 Water challenges in Semarang

Source: Cascading Semarang Phase 2 Report

Water Challenges in Semarang:

- Surplus water in rainy season There are 21 rivers located in Semarang, some of which regularly flood. Flash flood is also caused by poor drainage infrastructure, environmental degradation in the upstream area, sedimentation in the downstream area, poor maintenance and high precipitation. With an increase in occurrence of extreme weather events caused by climate change and the constant growing pressure of urbanisation, Semarang is increasingly vulnerable towards flooding.

1- Feeding the industry - Recharging Aquifers New water Reservoirs 2- Feeding the industry - Industrial zones 3- Re-Channeling the city - Canals for recharging shallow aquifers 4- Spongy Mountain Terrace - Urbanization in residential zone 5- Spongy Mountain Terrace - New water reservoirs 6- Spongy Mountain – Green bio-corridors

Fig.121 Map showing the context of Semarang and the overall project concept Source: Cascading Semarang Phase 2 Report

The lower areas of Semarang deal with most water issues, like floods and pollution, while the mountainous area suffers from a scarcity of drinking water, landslide and flash floods. Short of steady supply from other sources, both households and industry use ground water, leading to land subsidence of up to 17 cm/yr in some locations. This, combined with increased surface runoff due to increase in impermeable surfaces, regularly cause flash flooding. Combined with the increasing threat of sea level

- Water Scarcity during rest of the year Droughts are another main concern affecting Semarang, due to the clear seasonal shift. Inadequate network of piped water supply has given way to The lack of sustainable and reliable water supply has led to the exponential growth of private groundwater wells and the overexploitation of the groundwater. Insufficient water supply has also impacted the livelihood of local farmers. Vicious cycles and challenges in Semarang:

interdependent

The manner in which the city is currently developing, is not sustainable and lacks resilience due the following factors:

Precedents- Cascading Semarang | 64

- Land subsidence damages infrastructure making coastal properties uninhabitable - Coastal industries face increasing flood risks due to climate change and land subsidence, consequently impacting the economy from reduced revenue - Upstream urbanization without measures to increase the water retention capacity in the upstream areas will further elevate flood risk causing additional upstream migration and urbanization - Possible groundwater depletion and higher rainfall variability increases the risk of water scarcity

The project adopts a systemic approach to address the different water-related concerns of Semarang. Accordingly, five concepts focusing on different steps of utilizing rainwater have been proposed. (i) Spongy mountain terrace (ii) Re-channelling the city (iii) Feeding the industry (iv) Micro interventions (v) Recharging the aquifer

Fig.123 Causes of water problems in Semarang

Fig.124 Proposals to resolve the water problems in Semarang Source: Cascading Semarang Phase 2 Report

65 | Precedents- Cascading Semarang

1. Spongy mountain terrace:

2. Re-channelling the city:

‘Spongy Mountain Terraces’ imply the creation of nature-based adaptive systems, which allow for the capture, storage and reuse of water in the uphill areas of Semarang thereby minimizing the impact of runoff in downstream areas. The uphill interventions focus on improving spatial conditions by implementing new ecological conservation areas, mitigating landslide risk and enhancing water retention in agricultural areas. Thereby, flood risk in the downstream areas of the city will be reduced and water supply will be more stable throughout the year.

This strategy aims at the improvement of inner city urban water management, creating additional capacity for the storage and regulation of waterflow. Storing stormwater locally and discharging it slowly after the storm, reduces the risk of pluvial and fluvial floods downstream. This system promotes the local handling of stormwater in contrast to the current approach- moving the water masses downstream. [5]

4 Delay

1234-

Store

Landslide Resilient Neighbourhood Store and delay Shallow aquifer recharge Feeding the industry Convey

2+3

1+2

Cleanse

2+3+4

AGRICULTURE Capture and Provide

URBAN AREAS Store and Reuse Protect from Landslides

NATURE / FOREST Retain and Infiltrate

RIVER PARK Retain and Infiltrate

Fig.125 Tools for spongy mountain terraces and their location of adoption Source: Cascading Semarang Phase 2 Report

The Terraces will release new land for new urban developments, stimulate new urban typologies and new ways of living with water.

1- Terraced jungle 2- Wetland park 3- Water squares

4- Canal-front 5- Stepping stones 6- Kampung square

Fig.126 Proposed interventions for rechannelling the city Source: Cascading Semarang Phase 2 Report

Precedents- Cascading Semarang | 66

PROJECT

LOCATION

YEAR

APPROACH

Sabarmati Riverfront Development Ahmedabad, 2006Engineered India Present

Cheonggyecheon Stream Restoration

IMPLEMENTABLE SOLUTIONS (i) Interceptor drain plugging sewage outfalls in the river (ii) Self-financing model by cashing-in on the reclaimed land

2005

(i) Double interceptor drain plugging sewage outfalls in the river, while proving source of clean water entering Engineered + the stream Nature-based (ii) Ecological segment focussing on provision of undisturbed natural habitat for improving biodiversity

Taizhou, China

2004

(i) Designed to manage the interaction of the natural matrix and the human matrix Ecological/ (ii) Secluded Nature-based biodiversity islets (iii) Nature-based solution as stormwater filtering system

Shenyang, China

2003

(i) Agricultural Ecological/ landscape as part of an Nature-based urbanized environment

2010

(i) Using the porosity of natural landscape elements as stormwater Ecological/ filtering systems Nature-based (ii) Leaving a natural wetland undisturbed to preserve and maintain an ecological balance

Seoul, South Korea

The Floating Gardens- Yongning River Park

Shenyang University Park

Qunli Stormwater Park

Haerbin, China

67 | Precedents- Summary

PROJECT

LOCATION

YEAR

APPROACH

IMPLEMENTABLE SOLUTIONS

Liupanshui Minghu Wetland Park

Liupanshui, 2012 China

(i) Using terraced ponds to delay, store, Ecological/ and filter runoff Nature-based (ii) Use of low maintenance, native species

Qian’an, China

(i) Recovering the natural hydraulic pattern of a basin (ii) Adding natural Ecological/ cleansing systemsNature-based wetlands at the nodes (iii) Introducing ponds to reinforce the retention capacity of the basin

Recovering the Mother River- The Sanlihe Greenway

2010

The Deltaworks

Netherlands

19501997

Engineered

(i) Dykes as a defensive strategy to fend from sea level rise and marine flooding

Room for the Rivers (Ex. strategy - Dyke Relocation)

Nijmegen, 2016 Netherlands

Cascading Semarang

Semarang, Indonesia

(i) Retreating from flood plain is primary in allowing for rivers Engineered + to swell and thereby Nature-based reducing the high water levels and associated flood risks

(i) Strategic approach ranging from large scale strategy of transforming the landscape into a sponge, to micro2019: Engineered + interventions Compet Nature-based applicable at a single ition house/neighbourhood entry level are essential to addressing complex water issues resulting from inter-dependent issues

Precedents- Summary | 68

As introduced in the first section of the report, the ICRERP focuses on rapid draining of stormwater through river channel upgrades in the Cooum river. Contrasting to the above linear approach, the strategy proposed in this report is interventions on a range of scales: 1. REGIONAL SCALE: The factors affecting infiltration capacity are- Intensity and duration of rainfall - Amount of water in the soil - Slope of terrain - Nature of surface material - Extent and type of vegetation ‘Absorb’- By leveraging infrastructure (Road/Rail Network) as Bio-Corridors, it is possible to utilize the enormous lengths of State and National Highways, which are basically giant stretches of asphalt, to become carriers of green infrastructure. Thereby, nature of the surface material and the extent of vegetation are optimized. Upstream tree cover management being most effective at slowing and retaining moderate floods before soil saturation (Bathurst et al. 2011), infiltration capacity can be significantly improved by leveraging transportation infrastructure to become carriers of green infrastructure.

‘Coastal fortification’- Climate change is increasing the risk of coastal flooding through its effects on sea level rise and the intensity of cyclones. The traditional grey infrastructure components to combat this hazard is the use of embankments, sluice gates, dykes and seawalls. Green infrastructure components such as Mangrove forests can provide effective protection against coastal flooding.[24] Research shows that mangrove conservation can pay for itself in flood protection, thus being an effective, comparatively economical, and resilient solution.[36] Mangroves can decrease wave energy and storm surges, thereby serving as natural defences against rising sea levels. Mangroves are salt-tolerant plants of tropical and subtropical intertidal regions, that are a part of the coastal ecosystems which can act as buffers against sea-level rise as well as against natural hazards that bring intense wind, rainfall, or storm surge, and are additionally beneficial due to their large carbon storage capacities.[24]

Fig.128 Mangroves stabilize sediments and attenuate waves

Source: WRI/Flickr

Potential bio-corridors

CMA

National & State highways

Chennai City

Fig.127 Map showing highways passing tree cover areas potentially as bio-corridors

71 | Strategy- Regional Scale

2. BASIN SCALE: ‘Revive’- “Kudimaramathu” is an ancient community custom that involves desilting of local tanks prior to the arrival of the monsoon to reap maximum benefits from the rain. This is a dying traditional practice of Tamil Nadu that can revive the ancient wisdom of water management and be promoted to make aware of the significance of the tanks to the farmers.

Replacing the current unsustainable agricultural practices (Fig.130) with a more sustainable form such as Agroforestry (Fig.131), will be a resilient and economically viable option. 1

1234-

Carbon storage Refuge for biodiversity Increased water retention & reduced erosion Diversified & increased revenue

Fig.131 Replacing with a more sustainable agricultural system such as Agroforestry

Fig.129 Revival of “Kudimaramathu” ‘Replace’- Over 20% of the water demand in the Cooum basin is attributed to the agricultural sector. Rice paddy is a predominant cultivation in the basin, employing flood irrigation. The traditional grey infrastructural approach to tackle the present agricultural context in the basin would be to reinforce engineered systems such as dams, irrigation/drainage canals, etc., while, embracing the green infrastructural approach would mean to opt for increasing the soil water retention and to the optimise/reduce the irrigation requirements. [24] 1

1234-

Use of chemicals: soil & water pollution Erosion through wind and rain Water intensive monocultural agriculture Slash and burn practices

Fig.130 Present Scenario: Water-intensive monocultural agriculture

‘Retain’- Around 80 surface waterbodies/ tanks are present in the Cooum basin, all of which today remain only outside the city limits of Chennai (Fig.132). The Water Resources Department (WRD) of Chennai has proposed to create additional storage in several tanks by deepening their foreshore area by 1m-2m.

Fig.132 Surface waterbodies and other inundation areas in the Cooum basin Augmenting these tanks waterbodies to improve their storage capacity will have a dramatic effect on urban flooding downstream, and will also help in improving the ground water storage. [37] Research specific to the Adyar basin corroborates that augmenting the tanks/waterbodies uniformly by 2m can neutralize the adverse effects of urbanization in 2050 during scenarios like 1 in 50-year floods. [38]

Strategy- Basin Scale | 72

implement energy generation from waste. Waste collection is proposed to be a paid service. Handing of segregated waste will be incentivized, thereby encouraging and enforcing waste segregation at source. Fig.133 Agricultural tanks upstreamcurrent scenario 1

1- Tree buffer: preventing encroachments 2- Pond-dyke model: Filter (phytoremediation) + Retain + Infiltrate 3- Bio-diversity islets

Fig.134 Agricultural tanks upstreamproposed strategy Rejuvenating the existing agricultural tanks/ surface waterbodies upstream to increase their retention capacity while functioning as systems of filtration and recharge (Fig.134) will supplement as sources of water supply. 3. CITY SCALE: ‘Assort, Privatize, Incentivize’- Solid waste management remains a major challenge for the city of Chennai, poor management of which, is incidentally also a cause of pollution and accretion of beds of the city’s drainage network. With the current solid waste management system, unsorted/poorly sorted waste typically ends up in landfills which are already overwhelmed and nuisance to the residents living near these dumping grounds. Inadequate waste disposal facilities contributes to much of the solid waste being dumped around drainage channels/water bodies. An effective way to overcome this would be privatize solid waste management and

73 | Strategy- City Scale

Fig.135 An example management model

solid

waste

Source: GPT, UK

In Fig.135, an example of a waste management model by GPT demonstrates the paths for waste from the source, through the Material Recovery Facility (MRF) illustrating how revenue opportunities can be achieved by commoditising recycled materials, ensuring the deviation from landfills. ‘Drain & Filter’With the highly urbanized setting of Chennai, the infiltration capacity is minimal, resulting in a heavy run-off. Owing to the relative flat terrain of Chennai, in addition to the inadequacy of drainage provisions, further exacerbated by the poor maintenance of the existing drainage systems, water inundation is rampant. The traditional grey infrastructure approach to tackle this would be provision of storm drains, pumps and outfalls, that solely focus out draining out the stormwater rapidly, consequently wasting out on the opportunity of

benefitting from potable water. A green infrastructural approach of supplementing with retention areas will store stormwater and thereby reduce drain and pump requirements. These systems will complement the grey infrastructure, imparting resilience avoiding instances of overwhelming during extreme weather events. [24]

Fig.137 Delineated hydrological pattern of the Cooum basin

In order to achieve this, the following green infrastructure tools are proposed to be implemented:

Rain garden

Bioswale

Constructed wetland

Sunken squares

Detention pond

Fig.136 Green infrastructure tools to be implemented at city scale Utilizing the hydrological pattern of the basin (Fig.137), streets and canals can function as draining and filter channels for the stormwater, before it joins the river course, thereby providing opportunities for storage/increased infiltration, thus delaying peak discharge, drastically reducing the risk of riverine floods. Additionally, a numerous streets are proposed to be realigned in the II masterplan of Chennai (Fig.138) which can include these green infrastructural elements in their realignment.

>45m wide

27m – 30.5m

18m – 24m

Fig.138 Streets to be realigned as per II Masterplan of Chennai

Data Source: CMDA

‘Riverine vigilantes’The ICRERP proposes resettling 14,257 families inhabiting the slums along the river corridor to locations outside the city limit. A potentially feasible and lowcost option of improving the slum conditions, reducing their environmental impact on the river was overlooked in favour of the high cost resettlement. [41] Reserving a part of the re-developed housing along the river for the families to be resettled, in lieu of riverine pollution vigil/maintenance, would be a more sociologically acceptable and costeffective solution.

Strategy- City Scale | 74

4. NEIGHBOURHOOD/BUILDING SCALE: Built-up structures comprising over 80% of the Chennai city, micro-interventions at the building scale will cumulatively bring about a huge impact. Such decentralized systems are more reliable as failure at one or more points do not make large parts of the city vulnerable. ‘Harvest’- Dense development in the city has resulted in sealed surfaces which evidently impacts permeability and therefore results in heavy run-off. This heavy run-off factor can be utilized by collecting and storing; harvesting the rainwater for future use. Though current bye-laws mandate rainwater harvesting structures, poor know-how and practices inconsiderate of the geological conditions have rendered these structures redundant and dysfunctional. Appropriate structures to harness the stormwater while reducing the extraction of groundwater, will also stop the receding of groundwater levels and salt water intrusion. [39] 1- Stratified pit: Filtration + Recharge

Percolation Pits

1- Underground filtration chamber 2- Underground water storage 1

Rainwater Harvesting

urban agriculture to treat (root-zone treatment) and re-use water at the source of the sewage generation, will not only immensely reduce the load on the centralized sewage treatment systems but also minimize the dependence on external sources for water supply. 1- Settling tank 2- Kitchen garden/ water treatment system 3- Underground water storage

1 2

Treat Store

Grey water Re-use

Rainwater Harvest

Fig.140 ‘Tackle’ for water circularity Simple changes such as avoiding the use of synthetic chemical-based cleaning products will make this strategy easily implementable. ‘De-compound’Currently, property boundaries are defined using masonry walls, and these being structures with negligible permeability, cause what is termed as the ‘compound wall effect’. These walls change the local overland flow paths and sometimes even block the local channels owing to inadequate provision of culverts. This in turn alters the local flooding pattern, protecting some areas while flooding the others. [39]

Fig.139 Tools for ‘harvest’

Another factor contributing to increased surface run-off is impermeable paving.

‘Tackle’- Going further beyond harvesting and utilizing rainwater is to enable water circularity by treating the greywater at the source and reusing it. Development models with integrated green infrastructural solutions in the form of

De-compounding walls and paving by implementing permeable materials with added layers of suitable green elements will enable fences to effectively and economically serve the purpose of preventing encroachment, and reducing

75 | Strategy- Neighbourhood/Building Scale

run-off when the pavements are made more permeable. 1- Masonry walls ‘compound wall effect’ 2- Fence with prickly vegetation 3- Permeable paving

‘Floating filter’- Portable, floating phytoremediation systems such as “floating islands” a product developed by Clean water, India can facilitate water treatment in urban contexts with space constraints. This works on the principle of rootzone treatment, and provide a concentrated wetland effect while serving as microhabitat for biodiversity, alongside giving an aesthetic uplift.

Fig.141 ‘De-compound’ for permeability ‘Harness’- Building roofs are large surface area which are otherwise obsolete offer multiple benefits by providing the opportunity to harness solar energy and space for increased green cover. Solar energy: As Chennai receives abundant solar energy round the year, incorporating the use of solar-powered devices such as solar water heaters, solar cookers, and solar panels are helpful steps towards urban resilience. Green roofs: As vegetation possess the ability to absorb and retain water, adding green roofs to buildings come with various advantages such as increased rainwater absorption, insulation, habitat for biodiversity, reduced surface temperatures, etc. Based on the cost factors, different models are adoptable such as simple terrace gardens, or water resilient extensive green roofs that can be easily be installed in apartment buildings. 2 1

1- Harnessing solar energy 2- Green roof

Fig.143 ‘Floating filter’ for phytoremediation Regional Scale:

Absorb

Coastal Fortification

Basin Scale:

Revive

Replace

City Scale:

Assort, Privatize, Incentivize

Drain & Filter

Riverine Vigilantes

Neighbourhood/Building Scale:

Tackle

Harvest

Decompound

Fig.142 Tools for ‘harness’

Retain

Harness

Floating Filter

Fig.143a Strategy across scales

Strategy- Neighbourhood/Building Scale | 76

1. REGIONAL SCALE: Leveraging Infrastructure as Biocorridors to ‘Absorb’- Similar to most developing nations, the infrastructural planning in India is realised giving maximum importance to the short-term economic factors, without consideration to the environmental impact. The country has extensive road and rail network, the maintenance of which ranges from the Central governed bodies to local Public Works Departments. India has 142,126km of National Highways (as of April 2019) which is a meagre 2.7% of country’s total road network, and the government has plans to increase it to at least 200,000km. Most of existing network of highways are being expanded to four or more lanes, and some existing roads are being reclassified as National Highways.

1- Slower traffic (7.2m wide- each lane 3.6m wide) 2- Faster traffic (10.8m wide- each lane 3.6m wide)

Fig.145 Current Scenario: National highways configured to rapidly drain stormwater

In such a context, reconsidering the present methodology of the highways configuration and transforming the existing network of transportational infrastructure by water-sensitizing them will implicitly reduce the surface runoff quotient of these roadways and improve their water retention capacity.

A 1- Slower traffic (7.2m wide- each lane 3.6m wide) 2- Faster traffic (10.8m wide- each lane 3.6m wide) A- Raingarden B- Bioswale

Fig.144 AH45: Asian/National Highway

79 | Interventions- Regional Scale

Fig.146 Proposed: Leveraging National highways as bio-corridors, increasing retention capacity (reduced run-off)

Median with water-intensive ornamental plants

3 lane highway Two-way service road

Increased runoff from impervious surfaces

1 2 2 1- Slower traffic (7.2m wide- each lane 3.6m wide) 2- Faster traffic (10.8m wide- each lane 3.6m wide)

Bioswale: Filter + Retain + Infiltrate Barricade replaced with rain-garden

2 2

1 3

1- Slower traffic (5m wide- each lane 2.5m wide) 2- Faster traffic (10.8m wide- each lane 3.6m wide) 3- Dedicated 2-wheeler lane (2m wide)

Fig.147 Current vs. proposed scenario of National Highways

Interventions- Regional Scale | 80

Fig.148 Existing configuration of highways

Fig.149 An impression of highways as bio-corridors

81 | Interventions- Regional Scale

Fig.150 SH114: State Highway

1- Fast traffic (7.2m wide- each lane 3.6m wide) A- Bioswale

Fig.152 Proposed: Leveraging State highways as bio-corridors, increasing retention capacity (reduced run-off)

1- Fast traffic (7.2m wide- each lane 3.6m wide)

Fig.151 Current Scenario: State highways contributing to increased run-off/reduced permeability

Fig.153 Current vs. proposed scenario of State Highways

81 | Interventions- Regional Scale

Fig.154 Outer Ring Road (ORR) intersection at Cooum river

Fig.155 Outer Ring Road (ORR) as means of radiating green cover along its length

Interventions- Regional Scale | 82

1- Slower traffic (7.2m wide- each lane 3.6m wide) 2- Faster traffic (10.8m wide- each lane 3.6m wide)

Fig.156 Current Scenario: State highways contributing to increased run-off/reduced permeability

1- Slower traffic (7.2m wide- each lane 3.6m wide) 2- Faster traffic (10.8m wide- each lane 3.6m wide)

Fig.157 Proposed: Leveraging Outer Ring Road (ORR) as a bio-corridor, increasing the retention capacity (reduced run-off)

83 | Interventions- Regional Scale

Agricultural fields

Area prone to inundation Elevated 3 lane highway

Flood plain & Cooum river

Fig.158 Current Scenario: Transportation infrastructure contributing to increased run-off/reduced permeability

Fig.159 Proposed: Leveraging Outer Ring Road as a bio-corridor, increasing the retention capacity (reduced run-off)

Interventions- Regional Scale | 84

2. BASIN SCALE: As introduced in the previous section of the report, all of the surface water bodies of the Cooum basin today remain only outside the city limits. Basin scale strategy of ‘Retain’ is proposed to be implemented for all existing waterbodies and to preserve them from encroachment. The intervention is detailed on a segment of the Cooum river (Fig.160) which is dramatically dynamic owing to its relatively sharp bend, which can serve as a pilot for the remaining waterbodies in the basin. The intervention is elaborated also in the adjoining floodplain and reservoir. Incidentally, this floodplain is actively witnessing encroachment (Fig.161). Research shows that a river's rate of migration is closely correlated with the sharpness of its bends; the sharper and tighter the bend, the faster the water flows, fuelling greater erosion speeding up the river’s migration. The influence of a sharp bend on erosion and migration occurs just downstream from the curve, not directly alongside it. [40] 0

200

400

800m

May 2002

Jan 2021 Cooum river Landfill

Reservoirs

Floodplain

Hydrological pattern

Fig.160 Dynamism around the river

Fig.161 Satellite image of the Cooum river ~3km downstream the intersection of ORR

85 | Interventions- Basin Scale

Interventions- Basin Scale | 86

Fig.162 Rejuvenated river corridor and reservoirs in the Chennai Metropolitan Area and beyond

Floodplain to be restricted as a nodevelopment zone

Protected Floodplain:

Volume 1.5x

Min. 90m wide

Regularized fluvial corridor:

Increased room for the river

Promoting biodiversity & preventing encroachments

Green buffer:

Increased water storage capacity while functional as stormwater filtrating systems

Augmented reservoirs:

Scenario 1:

For most part of the year

Reservoir overflow:

Canal directing overflow from augmented reservoirs upstream

Increased room for the river:

Flood basin in dynamic curves of the river/locations where water collects; as inferred from the diachronic map

Riparian zone:

Hydrophilic plant species capable of phytoremediation

Green buffer:

Promoting biodiversity & preventing encroachments

Scenario 2:

During extreme weather events

Scenario 3:

During exception weather events- overflow from the augmented reservoirs upstream reaching the river

Fig.163 A: River-edge and floodbasin in the Chennai Metropolitan Area and beyond

87 | Interventions- Basin Scale

Interventions- Basin Scale | 88

Fig.164 Section through the rejuvenated river corridor in the Chennai Metropolitan Area and beyond

1- Green buffer: Promoting biodiversity & preventing encroachments 2- Riparian zone: Hydrophilic plant species capable of phytoremediation 3- Increased room for the river: Flood basin in dynamic curves of the river/locations where water collects

1 3

Pond-dyke model:

Cascading profile of pond-dyke model facilitating retention, filtration, and infiltration

Biodiversity islet Green buffer:

Promoting biodiversity & preventing encroachments

Fig.165 B: Varying water levels in an augmented reservoir with seasonal variability

89 | Interventions- Basin Scale

Interventions- Basin Scale | 90

Fig.166 Schematic section through the augmented reservoir B

1- Green buffer: Promoting biodiversity & preventing encroachments 2- Pond-dyke model: Cascading profile of pond-dyke model facilitating retention, filtration, and infiltration 3- Biodiversity islet

1 3

Augmented reservoirs sustainability:

and

material

Taking into account the number and extent of reservoirs proposed to be augmented, it is evident that very large quantities of earth will be excavated. With over 2500 families to be rehabilitated from the areas reclaimed for the Cooum river rejuvenation alone, and the ever-growing demand for housing for the increasing population, the most suitable application for the soil excavated from the augmented reservoirs is for it to be used as a construction material.

Depending on the composition of the excavated earth, ad-mixtures/stabilizers will be added to make it usable as infill material in the form of stabilized mud blocks, rammed earth walls, panels/shells, etc.(Fig.167) These mud-blocks and walls will be prepared in-situ, eliminating the need to be processed at a centralized location, shortening the supply chain and the associated carbon footprint.

Earth excavated to augment reservoirs

Stabilized mud blocks:

(excavated earth + stabilizers)

Moulded + Compacted



Sun-dried



In-fill construction material

Rammed earth walls:

Moulded

Rammed/Compacted

Rammed earth walls

Fig.167 Excavated earth as construction material

91 | Interventions- Basin Scale

Perforated screens

3. CITY SCALE: The intervention is detailed on a segment of the Cooum river in the city (Fig.168, 167) that has a relatively sharp meander and a significant number of areas to be resettled- providing a higher scope of redevelopment along the riverfront.

Cooum river

Slums (Source: ICRERP)

Additionally, when overlayed with the delineated hydrological pattern, a number of opportunities are observed that can potentially be integrated with green infrastructure along the natural drainage pattern (Fig.170).

Areas to be resettled (Source: ICRERP)

Areas inundated during 2015 floods (Source: IWMI/JAXA)

Fig.168 Areas within the city along the Cooum river prone to inundation 0

200

400

800m

Fig.169 Satellite image of the focus area for city scale interventions

Interventions- City Scale | 92

Dec 2000 1

2 2 4 3 1

4: Before

Oct 2020 Cooum river

Un-built spaces

Fig.170 Evolution of un-built spaces

93 | Interventions- City Scale

4: During metro construction

Fig.171 Condition of along the Cooum river and its surroundings

Interventions- City Scale | 94

100m

400m

Public parks/play areas

200m

Riparian zone

Fig.172 Masterplan showing city scale interventions

Linear park

Constructed wetland/detention pond

11 Community spaces

Sunken squares

Sponge streets

Residual space transformed as a stormwater retention area

Retention pond:

Min. 50m wide

Regularized fluvial corridor:

Stepped public space allowing for stormwater retention

Sunken squares:

Hydrophilic plant species facilitating phytoremediation

Riparian zone:

1- Reclaimed areas- Considering 70% to be residential spaces and the average number of storeys as 1.5: ~67,200Sq.m

4- Aqueduct connecting to the retention pond functioning as a bye-pass during exceptional weather events

2- Network of water-sensitized with the integration of infrastructure

streets green

5- Proposed built-forms for short-term development. 15% of the residential spaces, 10% of retail spaces allotted for occupants of reclaimed areas: ~28,500Sq.m (42% of reclaimed extent)

3- Locating constructed wetlands at the nodes functioning as natural waterfiltrating systems

6- Location for long-term development. 15% of the residential spaces, 10% of the retail spaces allotted for occupants of the reclaimed areas: ~12,500 Sq.m (18% of reclaimed extent)

Fig.173 Serviceability of constructed wetlands and relevance of ‘Riverine Vigilantes’

95 | Interventions- City Scale

1- Element 1 of vernacular building typology ‘Muttram’: built form wrapping around a central gathering space

2- Making the built-form penetrable to improve accessibility to the riverfront

5- Vertical expansion

6- Element 3 of vernacular building typology ‘Thottam’: Utilizing rooftops as productive spaces and passive energy saving systems

3- Element 2 of vernacular building typology ‘Thinnai’: Adding opportunities of interaction serving as pit-stops for passers-by

7- Ground floor: Retail spaces; 10% allotted for occupants of reclaimed areas. Upper floors: residential spaces; 15% of the total residential area allotted for occupants of reclaimed areas

4- Vertical expansion

8- Southern and western facades of the proposed built-forms to have perforated mud-blocks ‘jaali’ to reduce heat gain and modulate the humidity levels

Interventions- City Scale | 96

8 2

Fig.174 Scenario 1- Along the rejuvenated riverfront

97 | Interventions- City Scale

1- Pop-up market: Flexible public space for events/pop-up markets 2- Sunken square: Public spaces with water-retention capability 3- Constructed wetland: Natural water filtrating system as well as a public space 4- ‘De-compounded’ roads: Existing roads are water-sensitized by the use of permeable paving materials and replacing the central median with a bio-swale/rain garden 5- Raingarden 6- Proposed developments: 15% reserved for occupants of reclaimed areas 7- Stepped river edge: Accessible river edge with plant species facilitating phytoremediation 8- Public park along riverfront

1- Additional room for the river 2- Sunken square: Public spaces with water-retention capability 3- Retention pond: An accessible stepped public park functioning as a retention pond during exceptional weather events (>100 yr flood) 4- Community spaces: Proposed developments enclosing community spaces such as play areas, parks, amphitheatres, veg. gardens, etc. 5- ‘De-compounded’ roads: Existing roads are water-sensitized by the use of permeable paving materials and replacing the central median with a bio-swale/rain garden 6- Bioswale as an ‘aqueduct’: During exceptional weather events, overflow of the river is conveyed to the retention pond, which on fillingup will convey the water downstream

Fig.175 Scenario 2- Retention pond functional during exceptional weather events

Interventions- City Scale | 98

1- Tree trenches: Trees of varieties supporting soil remediation, with in-built seating on trench periphery 2- Stepped river edge 3- Additional room for the river 4- Proposed developments 5- Constructed wetland: Natural water filtrating system as well as a public space 6- Ramps: Enabling accessibility to lower levels 7- Riparian zone: Hydrophilic plant species facilitating phytoremediation 8- Sunken square: Public spaces with water-retention capability 9- ‘De-compounded’ pedestrian streets: Permeable surfaces from repurposed material

Fig.176 Scenario 3- Along the rejuvenated riverfront

99 | Interventions- City Scale

Interventions- City Scale | 100

2m 2m

50m

Fig.177 Scenario 3- Section along the rejuvenated riverfront

Stopping existing sewage outfalls and redirecting them to STPs (as located in ICRERP)

DI Drainage interceptor:

2.4m

2m 2m 8m

2.4m

101 | Interventions- City Scale

Fig.178 Scenario 3- Axonometric view along the rejuvenated riverfront

1- ‘De-compounded’ pedestrian streets: Permeable surfaces from repurposed material 2- Proposed developments: 15% reserved for ex-occupants of reclaimed areas 3- Pedestrian bridge: Connecting the two banks with pedestrian bridges, encouraging slow mobility 4- Flood basin: Additional room given to the river in areas prone to inundation 5- Stepped river edge 6- Rammed earth seating: in-built seating on constructed wetland periphery

Fig.179 Scenario 4- Along the rejuvenated riverfront

Interventions- City Scale | 102

103 | Interventions- City Scale

Fig.180 Scenario 4- Section along the rejuvenated riverfront

Stopping existing sewage outfalls and redirecting them to STPs (as located in ICRERP)

DI Drainage interceptor:

2.4m

DI 2m

2.4m

Interventions- City Scale | 104

Fig.181 Scenario 4- Axonometric view along the rejuvenated riverfront

105 | Interventions- City Scale

Fig.182 An illustration along the rejuvenated riverfront

STRATEGY

SHORT TERM

MEDIUM TERM

LONG TERM

Absorb: Leveraging highways as bio-corridors Revive: Ancient community practices Replace: Conventional agriculture with Agroforestry Retain: Augmenting upstream water bodies Assort, Privatize & Incentivize: Solid waste management Drain & Filter: Streets & Open spaces with green infrastructure Riverine Vigilantes: Rehabilitating encroachments Coastal fortification: Mangrove plantation Harvest: Rainwater saving Tackle: Greywater treatment at source De-compound: Swapping surface materials and boundaries Harness: Utilizing roofs as space for harnessing renewable energy

Interventions- Timeline for Implementation | 106

INTEGRATED COOUM RIVER ECORESTORATION PLAN

AMPHIBIOUS CHENNAI Developing Chennai's watersensitivity and planning for the city's water resilience following a strategic approach

Aim of the project

Cooum river rejuvenation and riverfront development

Location of intervention

Initialises from a part of the Interventions proposed at various scales- starting from the Cooum river in the Chennai Metropolitan Area (Paruthipattu) to Regional Scale and extending to the mouth of the river the Building Scale, along with the Cooum riverfront development

Strategy adopted

Engineered methods (grey Integration of grey and green infrastructure) to facilitate rapid infrastructure to improve water draining of the stormwater retention capacity of the basin and to facilitate water use.

Governing hierarchy involved

State Government of Tamil Nadu

Proposed interventions will include the involvement of Central Government as well as the State Governments of Tamil Nadu and Andhra Pradesh

Timeline

Plan prepared in 2012/13, implementation underway

Based on the urgency, complexity and the hierarchy of governing bodies involved, interventions are perceived to be implemented within spans of 2-3 years (shortterm), 5-6 years (medium-term) and 9-10 years (long-term)

Fluvial corridor

River channel improvements are proposed by adding canals of varying widths inside the riverbed to improve the flood carrying capacity of the river.

More room is provided to the river, and flood basins are proposed in areas prone to inundation. Additionally, a network of green infrastructure are proposed to store/delay the discharge of stormwater.

Waste management

1. Floating debris in the river are 1. Solid waste to be managed by proposed to be collected with 'Assort, Privatize, the help of boom barriers. Incentivize' model. 2. Sewage outfalls in the river are 2. Green infrastructural plugged by the introduction of elements functioning as an interceptor drainage running natural filtrating systems parallel to the river. will facilitate a circular 3. Sewage is proposed to diverted water system/discharge and treated at 6 new modular treated grey water into the sewage treatment plants. river. 3. Residual organic matter diverted to the 6 modular STPs proposed by ICRERP.

107 | Interventions- ICRERP vs. Amphibious Chennai

4. Sewage outfalls in the river are plugged by the introduction of an interceptor drainage running parallel to the river. Flora

1. Plant species of commercial value are proposed 2. Mangrove species are proposed in areas of marine influencecloser to the coast

1. Native species promoting biodiversity and/or phytoremediation are proposed 2. Mangrove species are proposed in areas of marine influencecloser to the coast

Resettlement of exoccupants of the reclaimed areas

Moved to locations outside the city

Relocated within the neighbourhood by allotting 15% of the newly developed residential buildings in the reclaimed areas/surroundings in lieu of working as riverine vigilantes for maintenance of the river corridor.

Interventions- ICRERP vs. Amphibious Chennai | 108

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[2]www.health21initiative.org/wpcontent/uploads/2017/08/2010-GlobalWater-Crisis-and-Food-Security.pdf

[18]chennaimetrowater.tn.gov.in/initiativ es.html

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[19]www.chennairivers.gov.in/PDF/Executiv eSummary-ICRERP.pdf

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[20]www.researchgate.net/publication/2560 43922_Sea_Level_Rise_Impact_on_Major_Infr astructure_Land_and_Ecosystems_Along_the_ Tamil_Nadu_Coast

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111 | References

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[33]www.dutchwatersector.com/news/roomfor-the-river-programme [34]www.huduser.gov/portal/periodicals/em /winter15/highlight3_sidebar.html [35]www.hnsland.nl/en/projects/roomriver-nijmegen [36]www.phys.org/news/2020-03mangrove.html [37]www.thehindu.com/news/cities/chennai/ thazhambur-lake-brimming-withwater/article33427675.ece [38]www.mdpi.com/2073-4441/12/10/2875/htm [39]www.yumpu.com/en/document/read/378600 18/chennai-terrain-guide-rainwaterharvesting [40]www.jsg.utexas.edu/news/2019/02/sharp -bends-make-rivers-wander [41]www.researchgate.net/publication/2656 25289_Salvaging_and_Scapegoating_Slum_Evi ctions_on_Chennai's_Waterways

References | 112

Amphibious Chennai: Systemic Approach to Water Sensitivity

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Amphibious Chennai: Systemic Approach to Water Sensitivity