Vinay Nikam and Kapil Gupta

IIT Bombay , Mumbai, India

Flood Resilience Study for Mithi River Catchment in Mumbai, India

International Conference on Flood Resilience Experiences in Asia and Europe 5-7 September 2013

Exeter, UK

Objectives of the study

• To carry out a flood damage assessment in the Mithi River

catchment and suggest resilience measures

•Scenarios considered

1. Three rainfall return periods I. 1 in 1 year II. 1 in 10 years III. 1 in 100 years

AND 1. Climate change

a. Business as usual b. Uplift factor of 1.20 applied to rainfall

Description of the Mithi catchment

• Catchment area- 7,295 Ha

• Length of river - 17.84 km • Annual average rainfall 2430

mm (Santa Cruz) • 95% falls during the monsoon

months from June to September

• 70 % of this rainfall occurs in

July and August • 50 % of this occurs in just 2-3

events

Mumbai

MithiRiver

Mumbai

Mithi River catchment (study area)

India

MithiRiver

Mumbai

Mithi River catchment (study area)

Mumbai

Mithi River profile

(Government of Maharashtra, 2006)

Flood history and mitigation measures

• 26 July 2005, major flood due to 944 mm rainfall in 24 hours-

60% city submerged, transport paralyzed, over 500 dead

• Mitigation measures undertaken by Municipal Corporation

1. Installation of real time rainfall alert system in 2006

2. Restoration and widening of Mithi River

3. Construction of holding pond/weir

4. Construction of flood protection walls for first 7.80 km

5. Retaining wall for the remaining (approx 8.0 km) length of river

in progress

Methodology

1. Population forecast provided by planning authorities

2. MIKE 11 used for flood simulation and water levels computed

for the three rainfall scenarios

3. Flood spread and depth

4. Depth damage curves

5. Vulnerability map

6. Flood damage return period curve

Combined scenarios for the Mumbai

Optimistic

Pessimistic

BAU

Population forecast

Optimistic

Pessimistic

BAU

Rainfall scenario

1 in 10 years

1 in 100 years

1 in 1 year

Climate change

uplift factor

1.20

BAU

Adaptive capacity

Adpatation 2

Adpatation 3

Adaptation 1

0

2

4

6

8

10

12

14

16

18

1901 1911 1921 1931 1941 1951 1961 1971 1981 1991 2001 2011 2021 2031

Po

pu

lati

on

(m

)

Year

Pessimestic BAU Optimistic

BAU

Pessimistic

Optimistic

Population forecast

12

13

14

15

16

17

2001 2011 2021 2031

Po

pu

lati

on

(m

)

Year Pessimestic BAU Optimistic

Pessimistic

Optimistic

BAU

Slum population scenarios

0

1

2

3

4

5

6

7

8

1981 1986 1991 1996 2001 2006 2011 2016 2021 2026 2031

Slu

m p

op

ula

tio

n (

m)

Year

Optimistic BAU Pessimistic

BAU

Pessimistic

Optimistic

Under pessimistic scenario, population is considered to remain steady after 2021 because most of the low-lying areas are already habitated by slums and saturated. Under optimistic scenario, slum population has been considered to be reduced to 39.5 % and 28.0 % for year 2021 and 2031 respectively

Rainfall intensities

Rainfall intensity (mm/h)

Return periods

Scenario 1 10 100

Business as usual (BAU) (Govt of Maharashtra,2006)

30 66 93

Uplift factor of 1.20 36 79 111

Mithi River in MIKE 11

Water level in river for 3 scenarios

0

5

10

15

20

25

30

1500 3500 5500 7500 9500 11500 13500 15500 17500

Le

ve

l (m

)

Chainage (m)

Bed level

111 mm/h (1 in 100 yr, uplift factor=1.20)

79 mm/h (1 in 10 yr, uplift factor=1.20)

36mm/h (1 in 1 yr, uplift factor=1.20)

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 100 yr I = 111 mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 10 yr I = 76mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 1 yr I = 36 mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 100 yr I = 111 mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 10 yr I = 76mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 1 yr I = 36 mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 100 yr I = 111 mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 10 yr I = 76mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 1 yr I = 36 mm/h

Flood spread and inundation (T=1 year)

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 100 yr I = 111 mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 10 yr I = 76mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 1 yr I = 36 mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 100 yr I = 111 mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 10 yr I = 76mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 1 yr I = 36 mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 100 yr I = 111 mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 10 yr I = 76mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 1 yr I = 36 mm/h

Flood spread and inundation (T=10 years)

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 100 yr I = 111 mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 10 yr I = 76mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 1 yr I = 36 mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 100 yr I = 111 mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 10 yr I = 76mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 1 yr I = 36 mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 100 yr I = 111 mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 10 yr I = 76mm/h

15-30 cm

30-60 cm

60-90 cm

90-120 cm

120-150 cm

Depth

T= 1 in 1 yr I = 36 mm/h

Flood spread and inundation (T=100 years)

Depth damage curves

Depth-damage curves

Land use map developed from

- field surveys

- interviews

Slum area

Building area

Mithi River

Depth damage curves

0.00

0.30

0.60

0.90

1.20

1.50

1.80

2.10

2.40

2.70

3.00

3.30

0 500 1000 1500 2000 2500

Dep

th (m

)

Damage (Rs. per sq.m.)

Slum at ground Slum with elevated plinth levels

Building at ground level Building with elevated plinth

50 INR/m2

200 INR/m2

250 INR/m2

500 INR/m2

Vulnerability

T= 1 in 100 yr I = 111 mm/h

50 INR/m2

200 INR/m2

250 INR/m2

500 INR/m2

Vulnerability

T= 1 in 10 yr I = 76mm/h

50 INR/m2

200 INR/m2

250 INR/m2

500 INR/m2

Vulnerability

T= 1 in 1 yr I = 36 mm/h

Vulnerability map (T=1 year)

50 INR/m2

200 INR/m2

250 INR/m2

500 INR/m2

Vulnerability

T= 1 in 100 yr I = 111 mm/h

50 INR/m2

200 INR/m2

250 INR/m2

500 INR/m2

Vulnerability

T= 1 in 10 yr I = 76mm/h

50 INR/m2

200 INR/m2

250 INR/m2

500 INR/m2

Vulnerability

T= 1 in 1 yr I = 36 mm/h

Vulnerability map (T=10 years)

50 INR/m2

200 INR/m2

250 INR/m2

500 INR/m2

Vulnerability

T= 1 in 100 yr I = 111 mm/h

50 INR/m2

200 INR/m2

250 INR/m2

500 INR/m2

Vulnerability

T= 1 in 10 yr I = 76mm/h

50 INR/m2

200 INR/m2

250 INR/m2

500 INR/m2

Vulnerability

T= 1 in 1 yr I = 36 mm/h

Vulnerability map (T=100 year)

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 100 yr I = 111 mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 10 yr I = 76mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 1 yr I = 36 mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 100 yr I = 111 mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 10 yr I = 76mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 1 yr I = 36 mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 100 yr I = 111 mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 10 yr I = 76mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 1 yr I = 36 mm/h

Flood damage (T=1 year)

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 100 yr I = 111 mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 10 yr I = 76mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 1 yr I = 36 mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 100 yr I = 111 mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 10 yr I = 76mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 1 yr I = 36 mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 100 yr I = 111 mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 10 yr I = 76mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 1 yr I = 36 mm/h

Flood damage (T=10 years)

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 100 yr I = 111 mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 10 yr I = 76mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 1 yr I = 36 mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 100 yr I = 111 mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 10 yr I = 76mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 1 yr I = 36 mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 100 yr I = 111 mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 10 yr I = 76mm/h

< 1 m INR

1 – 2 m INR

2 – 3 m INR

3 – 4 m INR

4 – 5 m INR

5 – 6 m INR

Damage

6 – 7 m INR

7 – 8 m INR

8 – 9 m INR

11 – 12 m INR

9 – 10 m INR

10 – 11 m INR

T= 1 in 1 yr I = 36 mm/h

Flood damage (T=100 years)

Damage – Return period curve

0.76

10.75

32.57

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

0 10 20 30 40 50 60 70 80 90 100

Dam

age

(M

IN

R)

Return period (year)

Summary and Conclusions

1. Flood simulation for present and future rainfall

intensities has been carried out

2. Flood impact assessment has been carried out

3. The depth-damage curves have been developed

4. Damage assessment has been carried out

Results

Study has resulted in identification of most severe flood

prone areas and expected damages

This will help in

1. Prioritising rescue and relief measures

2. Planning future mitigations measures

Future measures required

Need to setup flow gauges at various critical locations

and issue flood warnings based on real-time flood

forecast mechanism

Acknowledgements

• Research on the CORFU (Collaborative research on flood resilience in urban areas) project was funded by the European Commission through Framework Programme 7, Grant Number 244047

CORFU Mumbai Workshop (4-5 Feb, 2011)