URBAN EXPANSION AND FLOOD MANAGEMENT:

Is Chennai city and CMA Resilient?

S.Janakarajan Ph.D,

President, South Asia Consortium for Interdisciplinary Water Resources Studies

janak@mids.ac.in

Fundamentals of urban world • Coastal city • Density of drainage • Understand the water sheds • Understand the Hydro-geography • Elevation • Maintaining the given slope and gravity • Ecological hot spots • Growth and Development, land use

change and abuse of ecology

Impacts of Climate Change – Chennai spdcific fundamental

• Rising Sea Levels – 44 cm by 2070 (IPCC V AR); This estimate is now considered conservative

• 5-9 m when world 2 deg warmer (Paleo-climatic studies) Implications:

• Increased coastal extreme events • Coastal flooding • Seawater invasion and intrusion • Sea erosion • Climate refugees • Loss of coastal wet lands, estuaries

Source:

AR5 Chapter 13, WG1

ELEVATION EXERCISE AND SEA-LEVEL RISE Elevation Mapping exercise is the most essential exercise in the context of climate change LECZ – Up to 10 Meters distance from MSL is a vulnerable zone

In order to understand the floods it is important to understand

1.The rainfall pattern and characteristics of the monsoons

2.Upstream and downstream watersheds and ecology

3.What is the status of fundamentals in Chennai, , more so drainage systems

Average Annual rainfall in Poondi, Red Hills and Cholavaram, 1965-2012

Rainfall range Number of

years

<700 1

700-900 6

900-1000 3

1000-1200 11

1200-1400 10

1400-1600 11

>1600 6

rain fall per year

0

300

600

900

1200

1500

1800

2100

2400

1960 1970 1980 1990 2000 2010 2020

year

mm

Average annual rainfall at Chembaramabakkam, Poondi, Red Hills and

Cholavaram, 1965-2012

Source: CMWSSB

UPSTREAM – DOWNSTREAM WATERSHEDS

Number of tanks in Kancheepuram District

Sl.N

o

Name of the Taluk With Ayacut less

than 40 Ha

With Ayacut of 40

Ha and above

Total

1. Kanchipuram 107 151 258

2. Uthiramerur 82 175 257

3. Madhurantagam 153 232 385

4. Cheyyar 88 74 162

5. Chengalpattu 120 339 459

6. Tirukalukuntram --- --- ---

7. Sriperumpudur 112 178 290

8. Tambaram 47 84 131

TOTAL 709 1233 1942

Source: PWD records, Government of Tamil Nadu and Ground Water Perspectives – A Profile of Tiruvallur District,

SGWB, Tamil Nadu.

Number of Tanks in Tiruvallur District

Sl.N

o

Name of the Taluk With Ayacut less

than 40 Ha

With Ayacut of 40

Ha and above

Total

1. Tiruvallur 266 143 409

2. Uthukottai 43 166 209

3. Poonamallee --- 78 78

4. Ponneri 184 107 291

5. Ambattur 91 82 173

6. Gummidipondi 93 89 182

7. Tiruttani 154 70 224

8. Pallipattu 75 45 120

Total 906 780 1686

Source: PWD records, Government of Tamil Nadu and Ground Water Perspectives – A

Profile of Tiruvallur District, SGWB, Tamil Nadu.

WATER BODIES IN TIRUVALLUR AND KANCHEEPURAM DISTRICTS

DRAINAGE MAP OF

TIRUVALLUR AND

KANCHEEPURAM

DISTRICTS

DRAINAGE SYSTEM OF CHENNAI • Rivers • Macro Drains • Micro drains • Pallikaranai Marsh

Chennai’s unique water ways and drainage system North – Kosasthalayar river Central – Cooum river South – Adyar river Further South – Palar river To cut across all four – Palar river PLUS THOUSANDS OF TANKS Bur most neglected Most disrespected Most encouraged

Catchment area 235 km2

Max. length 15 km (9.3 mi)

Max. width 3 km (1.9 mi)

Surface Area 80 km2

Volume of water 9 km3

Surface elevation 5 m (16 ft)from the mean sea level

PALLIKARANAI WETLAND

Source: https://en.wikipedia.org/wiki/Pallikaranai_wetland

Velachery 1955 & 1971 USA Army Service Toposheet & ISO Toposheet

Velachery 1971 & 2010 ISO Toposheet & 2010 Google imagery

Radha nagar (Pallavaram 1955 & 1971 Radha nagar (Pallavaram 2010

Anagaputhur & Pallavaram 1955 & 1971 Anagaputhur & Pallavaram 1971 & 2010

Avadi , Vilinjambakkam & Palaripattu 1955 & 1971 Avadi , Vilinjambakkam & Palaripattu 2010

Ambattur Tank in 1955 Un-encroached Water spread area of the tank is 4.58 sq km

Ambattur Tank in 2010 Encroached and bifurcated

Water spread area of the tank is 1.91 sq km

Kodongaiyur Tank 1955 Kodongaiyur Tank 1971

Kodongaiyur Tank 2010

Villivakam Tank 1955

Villivakam Tank 2010

Fallacies current practices and approach

Flood relief and drought relief in rotation – eg., 2005, 2915 floods and 2016and 2018 droughts Remember: Cost or the value of collective damage plus the cost of Relief and Rehabilitation is several times more than the costs of prevention What does this convey? Current approach has been driven by political shrewdness rather than socio-economic rationality and realities HIDING BEHIND CLIMATE CHANGE

Summary of what needs to be done in the medium and long-terms (Contd)

• Recognize the importance of water ways of Chennai and acknowledge the fact that they

are lifeline of the city of Chennai; Protect them at any cost

• These water ways should be retrieved with respect to the A-Register (1900s) -

North - Kosasthalayar - originating in Kaverippakkam tank - carrying floods all

along and ends in Ennore creek

Central - Cooum - originating from the Kesavaram Anicut and cooum village -

carrying floods all along - joining sea near the University of Madras

South - Adyar - Chembarambakkam tank and Manimangala village -

Buckingham Canal - 100 feet wide - manmade canal - 438 km long - cuts across

all three as a buffer - (Remember, the river shall mean not only the bed-width but

also the right and left arm floods plains. Identify and restore 16 macro drains

• Link Pulicat and Muttukkadu through Buckingham Canal and allow the seawater /

brackish water flow and make it a waterway without sewage mixing with it

• Institute a state climate and weather unit - coordinating with IMD, ISRO, NOAA, BBC

and NASA

• Create a state data bank on disasters and extreme events and make them available to the

people

• Appropriate ecosystem valuation should be undertaken with a view to ascertaining the

loss of ecosystem and the ecosystem services and their impacts

• Environmental education for school children - with practical exercises to achieve

sustainability

Thank you