URBAN EXPANSION AND FLOOD MANAGEMENT: Is Chennai city … ppt 3... · 2019-08-05 · URBAN...
Transcript of URBAN EXPANSION AND FLOOD MANAGEMENT: Is Chennai city … ppt 3... · 2019-08-05 · URBAN...
URBAN EXPANSION AND FLOOD MANAGEMENT:
Is Chennai city and CMA Resilient?
S.Janakarajan Ph.D,
President, South Asia Consortium for Interdisciplinary Water Resources Studies
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