Inundation Risk of Storm Surge in the West Coast of Bangladesh

 

This book is outcome of an academic research under NUGELP of Nagoya University, Japan supported by JICA.

 

Foreword

I am very pleased that the book ‘Inundation risk of storm surge in the west cost of Bangladesh’ is being published. In this book I have identified the inundation risk levels derived from inundation depth and inundation velocity by applying a numerical model. This unveiled a new dimension for the geographers of Bangladesh. I believe Geographers can take the advantage by learning the fundamentals of storm surge simulation from this book and can apply similar techniques using GIS.

In this book I have find out different inundation characteristics and impact of two different cyclone within a common affected area. Super cyclone Sidr was a huge in term of its size, speed, affected area, affected population and the height of storm surge. Whereas, cyclone Aila was of medium category but intrude into far inland through the estuarine river channels due to the pressure of high tide and other external causes like the broken embankments by the river side’s. This caused a long term water logging in the Aila affected area. Interestingly, similar behavior was found in the storm surge simulation as well. If we could have performed such simulation earlier we could have enough information to plan for taking adequate mitigation measures.

Disaster management authorities and other stakeholders in Bangladesh can utilize this information for sustainable risk reduction interventions both for preparedness and for response activities in the west coast area of Bangladesh. Similar simulation could be carried out along the whole coastal area of Bangladesh and Geographers can take the lead for modeling such simulation by using GIS.

 

24 May 2014, Dhaka

 

Nazmun Nahar

Associate Professor

Department of Geography and Environment

University of Dhaka

 

 

 

Content

 

LIST OF FIGURES...Page ix

LIST OF TABLES...Page x

ACKNOWLEDGEMENT...Page xi

LIST OF ACRONYMS...Page xii

 

Introduction...Page 3

• Coastal Environment of Bangladesh...Page 4
• Coastal Area of Bangladesh...Page 5
• Coastal Livelihood of Bangladesh...Page 7
• Cyclone Hazard in Bangladesh...Page 8
• Chronology of Modeling Storm Surge...Page 8
• Rational for Modeling Storm Surge in Bangladesh...Page 11

 

Modeling Storm Surge and Risk Assessment...Page 15

The Study Area...Page 15

Computational Domain and Conditions...Page 15

Numerical Simulation...Page 17

• Typhoon Model...Page 18
• The SWAN Model...Page 19
• Storm Surge Model...Page 19
• Inundation Model...Page 21
• Simulation Flow chart...Page 23

Risk Assessment in the Study Area...Page 25

Data Sources...Page 27

 

Assessment of Cyclone Sidr...Page 31

Validation of Data Fields...Page 31

• Meteorological Field...Page 31  
• Storm Surge Field...Page 34
• Inundation Field...Page 36

Risk Assessment for Cyclone Sidr...Page 38

• Inundation Risk from Inundation Depth...Page 38 
• Inundation Risk from Inundation Velocity...Page 40
• Integrated Risk...Page 41                                                                                                                                                                         

Assessment of Cyclone Aila...Page 45  

Validation of Data Fields...Page 45

• Meteorological Field...Page 45
• Storm Surge Field...Page 48
• Inundation Field...Page 48  

Risk Assessment of Aila...Page 51 

• Inundation Risk from Inundation Depth...Page 51
• Inundation Risk from Inundation Velocity...Page 53
• Integrated Risk...Page 54

Inundation Risk Characteristics: Sidr vs Aila...Page 59

 

Conclusion and Recommendations...Page 67

 

References...Page 70

 

LIST OF GIGURES

Fig. 1: Coastal areas of Bangladesh (Zones and Regions)                                     6

Fig. 2: Location of the study area                                                                                 15

Fig. 3: Computational domain                                                                                       16

Fig. 4: Minimum height of polder blocks                                                                      17

Fig. 5: Outline of numerical models                                                                              18

Fig. 6: Calculation of typical overflow discharge                                                        22

Fig. 7:Estimation of inundation height                                                                          23

Fig. 8: Flowchart of Storm surge and Inundation model                                            24

Fig. 9: Validation sites for meteorological data field                                                   32

Fig. 10: Validation result of meteorological field                                                         34

Fig. 11: Validation sites for water level data                                                                35

Fig. 12: Validation result of water level field                                                                36

Fig. 13: Calculated inundations by cyclone Sidr                                                         37

Fig. 14: Observed and calculated inundation areas of cyclone Sidr                       38

Fig. 15: Calculated risk from inundation depth for cyclone Sidr                               39

Fig. 16: Calculated risk by inundation velocity for cyclone Sidr                               41

Fig. 17: Integrated inundation risk of cyclone Sidr                                                      42

Fig. 18 Validation of metrological field                                                                          47

Fig. 19: Validation of water level field                                                                            48

Fig. 20: Calculated inundations by cyclone Aila                                                          49

Fig. 21: Observed and calculated inundation map of cyclone Aila                           50

Fig. 22: Calculated inundation depth of cyclone Aila                                                  52

Fig. 23: Calculated inundation velocity of cyclone Aila                                               53

Fig. 24: Integrated inundation risk of cyclone Aila                                                        55

Fig. 25 Calculated maximum inundation depth by risk levels                                    59

Fig. 26: Calculated maximum inundation velocity by risk levels                                60

Fig. 27: Cyclone tracks                                                                                                       61

Fig. 28: Integrated inundation risk                                                                                    61

Fig. 29: Population affected by inundation risk                                                              62

 

 

LIST OF TABLES

Table 1: Computational domain and conditions                                             16

Table 2: Risk by inundation depth                                                                     25

Table 3 Risk by inundation velocity                                                                   26

Table 4: Possibility of evacuation by walk based on integrated risk            26

Table 5: Risk levels for the integrated inundation risk                                    26

Table 6: Sources of data collection                                                                    27

Table 7: Calculated risk assessment                                                                 61

Table 8: Observed physical & other characteristics and cyclone damage 63