Saqib Ehsan, M. Sc. Universität Stuttgart Institut für Wasserbau Lehrstuhl für Wasserbau und...

Saqib Ehsan, M. Sc.

Universität StuttgartInstitut für Wasserbau

Lehrstuhl für Wasserbau undWassermengenwirtschaftProf. Dr.-Ing. Silke Wieprecht

Risk and Planet Earth Conference 2009, Leipzig

Estimation of possible damages due to catastrophic flooding

for long-term disaster mitigation planning

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

Contents

- Introduction- 1D-Hydrodynamic modeling with MIKE 11- Development of an improved method for loss

of life (LOL) estimation- Loss of life (LOL) estimation for different

scenarios- Conclusions and Suggestions

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

Introduction

- Role of climate change in disaster management

- Possible extreme changes in climate as guidelines for the development of new concepts for disaster mitigation

- Drastic weather change - Heavy rainfall- Catastrophic flooding downstream of the dam- Risk to people and property

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

Introduction cont‘d

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

Introduction cont‘d

- Jhelum river valley downstream of Mangla dam in Pakistan

- One of largest earth and rock-fill dams in world- Main dam height ~125 m high above riverbed

(by Google earth)

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

Introduction cont‘d

Gross storage (original) 7.25 E+9 m3

Net storage (original) 6.59 E+9 m3

Catchment area of reservoir (original)

33,360 km2

Water surface area of reservoir (original)(at maximum conservation level)

253 km2

Power generation 1,000 MW

Crest length of main dam 2,561 m

Design capacity of main spillway 28,583 m3/s

Design capacity of emergency spillway

6,452 m3/s

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

1D-Hydrodynamic modeling with MIKE 11

Chenab River

Upstream Trimmu Barrrage

Jhelum Bridges

Rasul BarrageMalikwal

BridgeKhushab Bridge

Confluence Point

Suketar Nallah

Bandar KasJabba Kas

Kahan River

Mangla dam

Bunha River

-Project Reach: about 329km

-Different Hydraulic

structures

-Five tributaries between

Mangla and Rasul Barrage;

No gauges are existing there

-1D-modeling for unsteady

flow conditions

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

1D-Hydrodynamic modeling with MIKE 11cont‘d

Maximum Discharges

0

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35000

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70000

0 50000 100000 150000 200000 250000 300000 350000

Downstream chainage (m)

Max

. Q (

m3 /s)

40000 m3/s (withbridges)

40000 m3/s (withoutbridges)

50000 m3/s (withbridges)

50000 m3/s (withoutbridges)

MDF (61977 m3/s: withbridges)

MDF (61977 m3/s:without bridges)

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

1D-Hydrodynamic modeling with MIKE 11cont‘d

Rasul Barrage

High Flooding Scenarios (maximum water level)

150

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290

0 30000 60000 90000 120000 150000 180000 210000 240000 270000 300000

Downstream chainage (m)

Max

. wat

er le

vel (

m)

40000 m3/s (with bridges)

50000 m3/s (with bridges)

MDF (61977 m3/s: with bridges)

40000 m3/s (without bridges)

50000 m3/s (without bridges)

MDF (61977 m3/s: without bridges)

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

1D-Hydrodynamic Modeling with MIKE 11cont’d

Dam break Flood Routing (maximum discharges)

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0 30000 60000 90000 120000 150000 180000 210000 240000 270000 300000

Downstream chainage (m)

Max

. Q (

m3 /s

)

Case1 (with bridges)

Case2 (with bridges)

Case3 (with bridges)

Case1 (without bridges)

Case2 (without bridges)

Case3 (without bridges)

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

Rasul Barrage

1D-Hydrodynamic Modeling with MIKE 11cont’d

Dam break Flood Routing (maximum water level)

150

160

170

180

190

200

210

220

230

240

250

260

270

280

290

300

310

0 30000 60000 90000 120000 150000 180000 210000 240000 270000 300000

Downstream chainage (m)

Max

. wat

er le

vel (

m)

Case1 (with bridges)

Case2 (with bridges)

Case3 (with bridges)

Case1 (without bridges)

Case2 (without bridges)

Case3 (without bridges)

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

Development an improved LOL estimation method

LOLi = PARi x FATBASE x Fsv x Fage x Fmt x Fst x Fh x Fwar x Fev

LOLi = loss of life at a particular location ´´i`` downstream of the dam

PARi = Population at risk at a particular location ´´i`` downstream of the dam

FATBASE = Base Fatality rate of 0.15 (worst case of medium severity) (Graham, 1999), assuming an average value of 1.0 for all other factors with average conditions.

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

Fsv = Flood Severity factor

High Severity very likely 1.0Medium Severity unlikely 0.3Low Severity very unlikely 0.1

Fage = Age risk factor

A (<10yrs+ (>=65yrs)),B (10-15)yrs and C (15-64)yrs

Fage = 1.25 *A% +1.1* B%+ 0.8* C% (general form) Fmt = Material risk factor

Fmt = 1 * X % + 1.5 * Y % (general form)

Where, X= % of other type of houses, Y= % very low strength houses

Development an improved LOL estimation method

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

Fst = Storey risk factor Fst = 1 (for high severity and all house types)

Fst = 1- S % (for medium and low severity)

Where, S= % of more storey houses

Fh = Health risk factor; 3% disabled people Fh = 1 *H % + 1.25*D % (general form)

Where, H= % of PAR with avg. health, D= % of disabled PAR

Development an improved LOL estimation method

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

Fwar = Warning factor (Graham,1999)

Warning Flood Severity understanding Fwar

No No 1 Some (15-60min) Vague/unclear 0.7 Adequate (>60min) Precise/clear 0.3

Fev = Ease of evacuation factor

Warning Ease of evacuation Fev

No No 1 Some (15-60min) Some 0.7 Adequate(>60min) Good 0.3

Development an improved LOL estimation method

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

Loss of Life estimation

PAR downstream of Mangla dam (98-Census data)

0

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180000

200000

Downstream chainage (m)

PAR

(No.

of

Peo

ple

at r

isk)

PAR

Total PAR : 1178038

Urban PAR : 37%

Rural PAR : 63%

Estimated PAR is related to the highest flood event in the past

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

Loss of Life estimation

Estimated Total Loss of Life downstream of Mangla dam (98-Census data)

0 5000 10000 15000 20000 25000 30000

1

2

3

4

5

Sele

cted

Sce

nari

os

Total Loss of Life

LOL (MDF 61977 m3/s:without bridges)

LOL (MDF 61977 m3/s:with bridges)

LOL (50000 m3/s:without bridges)

LOL (50000 m3/s: withbridges)

1- Warning Initiation 30min after Failure 2- Warning Initiation 15min after Failure

3- Warning Initiation at Failure

4- Warning Initiation 1hr before Failure

5- Warning Initiation 2hrs before Failure

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

% Total Loss of Life for Different Failure Cases

1

1.5

2

2.5

3

3.5

4

4.5

0 50000 100000 150000 200000 250000 300000 350000

Max. Discharge (m3/s)

% T

otal

LOL

(%

dea

d pe

ople

)

%LOL (with bridges)

%LOL (without bridges)

Worst Case for Warning Initiation:

30 minutes after Failure

Loss of Life estimation

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

Cumulative Loss of Life due to Dam Failure

0

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0 25000 50000 75000 100000 125000 150000 175000 200000 225000 250000 275000 300000

Downstream chainage (m)

Cum

ulat

ive LOL

Failure Case1

Failure Case2

Failure Case3

% Cum. LOL up to 50Km: about 80% of Total LOL

% Cum. LOL up to 100Km: about 90% of Total LOL

Total LOLWorst Case for Warning

Initiation: 30 minutes after Failure

% Cum. LOL up to 25Km: about 68% of Total LOL

Loss of Life estimation

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

Conclusions and Suggestions

- Severe climate change can cause extreme flooding downstream of a

dam

- Estimation of possible damages is an important part of any dam

safety study

- Loss of life increases with the delay in warning initiation with respect

to dam failure

- For all dam failure cases, maximum LOL (~80%) occurs in first

50 km downstream of Mangla dam

- % total LOL for the worst case of Mangla dam failure is close to 4%

which seems to be very high

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

Conclusions and Suggestions

- LOL results clearly show the need of improvement in existing risk Reduction measures in order to reduce possible LOL due to Mangla dam failure

- More research is required to estimate

- ease of evacuation - risks posed by age groups - very low strength houses and more storey houses - Realistic estimation of possible LOL due to natural hazards like floods helps in long-term disaster mitigation planning

Risk and Planet Earth Conference, Panel 2 for Junior Scientists, 4th March 2009, Leipzig

THANKS FOR YOUR ATTENTION

QUESTIONS??

Saqib.Ehsan@iws.uni-stuttgart.de

www.iws.uni-stuttgart.de

Lehrstuhl für Wasserbau und Wassermengenwirtschaft

Institut für Wasserbau, Universität Stuttgart