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An investigation on the frequency and intensity of extreme
precipitation in Chennai city in the context of climate change
Rohith A N and K P Sudheer
Department of Civil Engineering, IIT Madras.
19 January 2018
Hydrologic Modeling Group
Department of Civil Engineering, Indian Institute of Technology Madras
HMG-IITM
Chennai Flood During December 2015
19 January 2018
Hydrologic Modeling Group
Department of Civil Engineering, Indian Institute of Technology Madras 2
Source: The Indian Express, Dec-4,2015
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Chennai City
19 January 2018
Hydrologic Modeling Group
Department of Civil Engineering, Indian Institute of Technology Madras 3
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Rapid Urbanization
19 January 2018
Hydrologic Modeling Group
Department of Civil Engineering, Indian Institute of Technology Madras 4
Renyi’s entropy
1991 – 0.4
2003 – 0.5
2016 – 0.9
2027 – 1.7
(Padmanaban et al., 2017)
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Causes
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Hydrologic Modeling Group
Department of Civil Engineering, Indian Institute of Technology Madras 5
Improper maintenance
Inadequate drainage capacity
Drainage water overflowing onto Avenue Road in Bangalore on Monday, ( The Hindu, December 18, 2012)
Waste Removal from drainage in B V K Iyengar road Bengaluru, (October 20, 2016)
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Chennai Rainfall
Average annual rainfall 1300 mm 73 rain days
Average Annual maxima 170 mm
December 1st 2015
Rainfall is 350 mm (Meenambakkam)
Rainfall is 425 mm (Nungambakkam)
350 mm is a 166 year return period event
The design intensity -39mm/h (T=2y,D=1h)
which is supposed to be more than 50mm/h
19 January 2018
Hydrologic Modeling Group
Department of Civil Engineering, Indian Institute of Technology Madras 6
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Precipitation Anomalies in Chennai City
19 January 2018
Hydrologic Modeling Group
Department of Civil Engineering, Indian Institute of Technology Madras 7
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Intergovernmental Panel on Climate Change (IPCC)
Gives guidelines for projection of climatic
variables.
The projections are General Circulation Model
(GCM) Simulations.
Emission Scenarios, (RCP2.6, RCP4.5, RCP6.0,
RCP8.5)
The simulations are at global scale
Downscaling is required.
19 January 2018
Hydrologic Modeling Group
Department of Civil Engineering, Indian Institute of Technology Madras 8
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GCM Projections
19 January 2018
Hydrologic Modeling Group
Department of Civil Engineering, Indian Institute of Technology Madras 9
GCM: Numerical
models representing
physical processes in
the atmosphere,
ocean, cryosphere
and land surface
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19 January 2018
Hydrologic Modeling Group
Department of Civil Engineering, Indian Institute of Technology Madras 10
Downscaling: Using information at coarser scale obtaining the information at finer scale
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Future Extreme Anomalies
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Hydrologic Modeling Group
Department of Civil Engineering, Indian Institute of Technology Madras 11
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Future Extreme Precipitation Events in Chennai
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Hydrologic Modeling Group
Department of Civil Engineering, Indian Institute of Technology Madras 12
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Changes in extreme precipitation magnitudes with respect to return period
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Hydrologic Modeling Group
Department of Civil Engineering, Indian Institute of Technology Madras 13
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Changes in return periods
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Hydrologic Modeling Group
Department of Civil Engineering, Indian Institute of Technology Madras 14
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Future IDFs
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Hydrologic Modeling Group
Department of Civil Engineering, Indian Institute of Technology Madras 15
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Conclussions
Dec 1st (166 year event) is expected to occur at 30year-rcp2.6,
31year-rcp4.5,
26year-rcp6.0,
37year-rcp8.5.
The design intensity -39mm/h (T=2y,D=1h)
This designed intensity (39mm/h, T=2y,D=1h)is expected to increase to 54 mm/h in the near future under rcp4.5
There is necessity to revisit the urban drainage design criteria.
19 January 2018
Hydrologic Modeling Group
Department of Civil Engineering, Indian Institute of Technology Madras 16
