IAHR 2015 - Vulnerability of the Bangladesh coastline to inundation under cyclone activity, Ciavola,...

This project has received funding from the European Union’s Seventh Programme for Research, Technological Development and Demostra>on under Grant Agreement No. 603458

Prof. Paolo Ciavola, Università di Ferrara-‐CFR, Ferrara, Italy [email protected]

Vulnerability of the Bangladesh Coastline to Inunda>on Under Cyclone Ac>vity: Past Records and DRR Strategies at Sandwip Island P. CIAVOLA (UNIFE-‐CFR), M.M. UDDIN (UNIFE-‐CFR) , E. DUO (UNIFE-‐CFR) , B. LEE (WMO), S.H.M FAKHRUDDIN (WMO)

36th IAHR World Congress 28 June – 3 July, 2015, The Hague, the Netherlands

Problem statement


Problem statement

Cyclones Tracking Over Bangladesh During the Twentieth Century

Frequency of cyclones/severe cyclones over the Bay of Bengal in different months

during 1891-‐2010


Most important recent events Dura/on: 29-‐30 April, 1991 Damage: widespread damage Death: 138,882 people Total Loss: US $ 2.07 billion Storm Surge: 4-‐6 meter

Dura/on: 14-‐16 Nov, 2007 Killed: 3,406 peoples Injured: 55282 Storm Surge: 5-‐6 m high

Source: DDM website


Study Site: Sandwip Island

•  The eleva>on of the island is lower than 5 m, and most commonly 2-‐3 m. Addi>onally, the sediments making up the islands are very soh, unconsolidated silts and clays.

•  Thus the landforms of the ac>ve delta are extremely changeable and are easily reshaped by, >dal ac>on, river discharge and ajack of cyclones


•  What is the historical records of cyclone impact on the island?

•  What DRR measures were present when historical events occurred? What are present now?

•  What is the current coastline change along the island? •  Set-‐up of an opera>onal Early Warning System at a demostra>ve level using DELFT-‐FEWS

•  Calibra>on of the EWS following installa>on of a local >de gauge and repeated surveys

•  What is the local percep>on of people occupying the island? How do they cope with disasters?

Research ques>ons


•  Analysis of records available from Bangladesh ins>tu>ons.

•  Topographic survey of eroding part of the island •  Analyses of Landsat imagery (1978, 1989, 2001, 2006, 2014) for shoreline change and land-‐cover change

•  ASTER DEM of the island (30 m resolu>on) •  Ground-‐truthing of DEM with comparison with surveys

•  43 interviews to key-‐end users from the island and 150 interviews to local residents, focussing on the percep>on if they are at risk and how they cope with problems like coastal erosion and cyclones

Methods


Physical Characteris>cs (surveys)

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Cyclone surge level

Cyclone surge level

Cyclone surge level

Cyclone surge level

Cyclone surge level

Physical Characteris>cs (surveys)


Evolu>on of the island (Landsat)

Year Difference (km2)

Erosion (Km2)

Erosion Rate(km2/yr)

Accretion (km2)

Accretion Rate km/y

1978-1989 -32.51 34.5 3.128 1.907 0.173

1989-2001 26.379 30.916 2.576 57.322 4.776

2001-2006 -11.955 23.133 4.626 11.286 2.257

2006-2014 -36.46 39.572 4.946 3.036 0.379

Erosion Accre>on


Land-‐use change (Landsat)

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Occupa>on growing from 7% (1989) to 26% (2001) to 37% (2014) of the total area in those three years

Agricultural land reduced drama>cally from 64% in 1989 to 23% in 2001 due to conversion into sejlements


Coping with coastal erosion

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Erosion

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Surge Flood Risk

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No

emba

nkm

ent


Possible cyclone inunda>on

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3 meter surge height

91 / 227 (km2)

6 meter surge height

171 / 227 (km2)


Coping with cyclones

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Erosion

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Management ac/ons implemented aGer

disasters

Construc>on of cross dam Island encircling embankment Warning system accuracy and >mely dissemina>on Risk relevant educa>on & adapta>on training Transport, health and communica>on development

Community Demands


•  Island with high coastal dynamics, the island has always existed, there is evidence in historical documents since the 16th century.

•  In the 1990s changed shape extending northwards. The 1991 cyclone might have played a role in this.

•  In the same period there was a change in land-‐use conver>ng agricultural land into forest and there was an increase in sejlements in the western part of the island

•  Simple bath-‐tub modelling shows that this is the area most vulnerable to cyclones as flooding

•  Future work will included the set-‐up of an opera>onal Early Warning System at a demonstra>ve level using DELFT-‐FEWS

Conclusions

Looking forward to a fruioul coopera>on!

! !

Thanks for your ajen>on

Accreting mudflat western side of Sandwip, February 2014

IAHR 2015 - Vulnerability of the Bangladesh coastline to inundation under cyclone activity, Ciavola,...

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