SPATIO – TEMPORAL ANALYSIS OF RAINFALL FOR MUMBAI

2012 International SWAT Conference
EFFECT OF URBANIZATION ON THE MITHI RIVER BASIN
IN MUMBAI: A CASE STUDY
P.E.Zope 1, T.I.Eldho 2 and V.Jothiprakash 3
Research Scholar , Dept. of Civil Engineering , IITB, Mumbai
2 Professor, Dept. of Civil Engineering, IITB, Mumbai
3 Associate Professor, Dept. of Civil Engineering, IITB, Mumbai
1
INDIAN INSTITUTE OF TECHNOLOGY, DELHI
URBANIZATION EFFECT
 Increased surface runoff in
annual stream flow.
 Increase magnitude of peak
runoff.
 Decreased lag time between
rainfall and runoff response.
 Increased rate of hydrograph
rise and recession.
 Decreased mean residence
time of stream flow.
 Topographical changes
 Population growth.
 Densification of structures.
 Less Evapotranspiration.
 No detension Basins.
Source : Dellur , 2003
EFFECT OF URBANIZATION
Heavy Rainfall
Intensities
Effect of Urbanization
Change in LU/LC
Inadequacy of Drainage
Channels
Tidal Influence
Urban Flooding
3
OBJECTIVES OF URBAN STORM
WATER MANAGEMENT SYSTEM
 To safeguard health , safety and property of
citizens/ residents.
 To reduce inconvience to citizens by having an
integrated approach.
 Better quality of life for the society.
 To achieve greater sustainability .
 To avoid floods .
 To improve the storm water quality .
GEOGRAPHY OF MUMBAI
 Lat 180N to 19.200N,
Long. 720E to 730E
 An area of 437.71 sq.
km.
 An ancient city
comprising seven
islands joined with
land filling.
 Divided into 24
Municipal
administrative areas
called wards.
 Coastal length of 140
Km.
 Average annual rainfall
of 2129 mm in the
monsoon months from
June to September.
 Limitations to cope up
the infrastructure with
population growth rate.
Source : MCGM
DELUGE ON 26TH JULY 2005
Hyetograph of 26th July 2005 rainfall :





419 people & 1600 cattle lost lives.
216 people lost lives due to flood related illness.
100,000 residential and commercial establishment.
30,000 vehicles.
22% of Mumbai’s land (excluding forest) inundated.
 Unprecedented downpour
of 944.2 mm. within 24
hours ending at 8.30 hours
on 27th July.
 While the Colaba
observatory recorded only
74 mm of rain.
 14:30 to 18:30 – 481.2 mm
 exceeded the rainfall
record of Cherapunji.
 Maximum tide level – 4.48
meter .
 Till 1989 – Average
rainfall – 2129 mm.
 2005-2006 – 3214 mm
FLOODING AT MUMBAI- 26 JULY2005:
FLOODING AT MUMBAI- 26 JULY2005:
JULY 2005 FLOODS IN MUMBAI
Source : MCGM
Flooding at Mithi River on 26th July 2005
EXISTING STORM WATER DRAINAGE SYSTEM IN MUMBAI
 The drainage system of
Mumbai is a mix of
simple drains and
complicated network of
rivers, creeks, drains and
ponds.
 Separate systems for
disposal of sewage and
storm water.
 Underground S.W .drains
in city and open in
suburb.
 Road side S.W. drainage
is designed for rainfall
intensity of 50mm/hr for
2 year return period.
Source : MCGM
Mithi River From Vihar Lake to CST Bridge
Mithi River From CST Bridge to Mahim creek.
Origin of Mithi River
Origin of Mithi River
Origin of Mithi River
Vihar Lake Overflow
DEM and Catchment Area
 As the corrected DEM generated from CARTOSAT -2009 gives perfect results
about stream network , it is considered for study area.
 Elevation ranges from 4.0 m to 380 m
Sub Catchment wise statement of Mithi River
Catchment Number
Catchment Area (Sq.Km.)
Catchment Number
Catchment Area (Sq.Km.)
1
1.24
13
1.24
2
2.233
14
0.525
3
0.728
15
8.234
4
0.446
16
2.719
5
0.938
17
4.741
6
0.347
18
10.342
7
0.774
19
5.938
8
0.695
20
0.642
9
0.573
21
4.072
10
6.357
22
1.082
11
6.481
23
0.508
12
5.227
24
2.757
Total
68.839
 Total catchment area of Mithi River consists of 24 sub – catchments.
 Total catchment area is 68.839 Sq.Km.
Slope Map
 Slope of the catchment varies from 0 to 62%.
 Very steep slope : 1:200 upto 4 Km from Origin.
 Slope : 1 :450 – from 4.00 to 7.50 Km
: 1:850 – from 7.50 to 12.0 Km
: 1:4000 – from 12.0 to 17.8 Km.
Change in River Course
 Runway of airport extended on the river course of Mithi.
 Development of reclamation , buildings and slums along the mud flat area of Mithi river
near Mahim bay.
 Construction of infrastructure such as roads , Bandra Kurla complex on the mud flat area
of Mithi.
Change in River Course
 During 1992-2009 , all
the mud flat area which
was acting as holding
pond , fully developed .
 River course of Mithi and
Vakola river reduced and
encroached drastically by
infrastructural
development , slums…
etc.
Change in River Course
 Runway of airport extended on the river course of Mithi.
 Development of reclamation , buildings and slums along the mud flat area of Mithi river
near Mahim bay.
 Construction of infrastructure such as roads , Bandra Kurla complex on the mud flat area
of Mithi.
Summary of Changes in Mithi River Course
Area
Encumbered(Sq.Km)
Net River course
area including mud
flats (Sq.Km)
Type of Changes
1966
nil
6.513
nil
2001
2.464
4.049
Airport Runway
extended,
Reclamation at
Mahim bay and
Bandra Kurla
complex area
2009
3.002
3.511
Entire Bandra-Kurla
complex area
reclaimed, some
part of Vakola basin
Year
Mithi River before July 2005 floods
Mithi Near Marol Industrial Estate, Andheri
(E)

Way to Airport from Saki Naka
River course of Mithi encroached on the banks by unauthorized slums reducing the width of river
drastically.
Mithi River before July 2005 floods
Moraraji Nagar Slum Encroachment
Mithi on Kurla – Saki Naka
Road
 Siltation / garbage in river course due to unauthorized slums on the banks of river.
Mithi River before July 2005 floods
Moraraji Nagar Slum Encroachment
Mithi on Kurla – Saki Naka
Road
 Extension of Runway within Mithi River Course.
Land Use- Land Cover ( LU-LC)
 Built up land :

in 1996 : 27%
 In 1972
:28.56%
 Water Body :
 in 1966 :
13.8%
 in 1972 :
9.96%
DD/MM/YY
Satellite/ Sensor
Resolution (m)
13th November 1972
Landsat/MSS
80
9th November 1992
Landsat/TM
30
27th November 2001
Landsat/ETM
30
6th March 2009
IRS P6/L-4
5
Land Use- Land Cover ( LU-LC)
For the year 1992
For the year 2001
For the year 2009
 Built up land increase from 27 % to 34.49% .
 Water body reduced to 8.73% from 20.15%.
 Due to change in month ( March & November ) of images , there is misclassification in open
land and vegetation.
Land Use- Land Cover ( LU-LC)
(In sq.km)
Land
use
1966
1972
1992
2001
2009
Open
land (%)
19.17
(27.85)
15.94
(23.16)
13.59
(19.74)
16.34
(23.74)
19.30
(28.18)
Vegetat
ion (%)
17.21
(25)
26.38
(38.32)
25.88
(37.59)
22.71
(32.99)
19.69
(28.60)
Water
body
(%)
13.87
(20.15)
6.86
(9.96)
6.39
(9.28)
6.7
(9.73)
6.11
(8.73)
Built up
land (%)
18.59
(27)
19.66
(28.56)
22.98
(33.39)
23.09
(33.54)
23.74
(34.49)
Total
68.84
 Due to change in land use , the
river course of Mithi reduced
drastically .
 Mud flats area which was earlier
acting as a holding pond ,
vanished completely due to
infrastructural development ,
urbanization and unauthorized
slums.
Improvement of Mithi River By Constructing Retaining Wall
SUMMARY AND CONCLUSION
 In urban flood estimation, effect of urbanization, land use change and hydrological
extremities is vital.
 In coastal cities, problem of flooding is due to high rainfall coinciding with high
tide.
 In Mithi river catchment built up area i.e. urban area is increasing drastically as
compared to in year 1966.
 From the analysis it is found that there is a rise in built up area from 27 to 34.49%
between 1966 and 2009, which is the main cause of increase in impervious surface,
which in turn increased the runoff resulting in severe flooding.
 In 1966 at downstream side of the river, there was huge open land, mud flat area
and wide channel area of river for smooth flow.
 In 2001, about 37.81 % of mud flat area has been encroached by unauthorized slum,
construction of building and infrastructural work reducing width of river and
smooth river flow.
 In 2009, 45.09 % of mud flat area covered by buildings and slum at Bandra Kurla
complex area, reducing the river width and flow drastically.