NOTES TECHNIQUES February 2017 TECHNICAL REPORTS No. 25 Socio-physical Vulnerability to Flooding in Senegal An Exploratory Analysis with New Data & Google Earth Engine Authors Bessie SCHWARZ, Beth TELLMAN, Jonathan SULLIVAN, Catherine KUHN, Richa MAHTTA, Bhartendu PANDEY, Laura HAMMETT (Cloud To Street), Gabriel PESTRE (Data-Pop Alliance) Coordination Thomas ROCA (AFD) Country Senegal Key words Data-science, Flood, Machine Learning, Satellite, Vulnerability AFD, 5 rue Roland Barthes, 75598 Paris cedex 12, France ̶ +33 1 53 44 31 31 ̶ +33 1 53 44 39 57 [email protected] ̶ http://librairie.afd.fr AUTHORS AUTHORS Bessie SCHWARZ, Beth TELLMAN, Jonathan SULLIVAN, Catherine KUHN, Richa MAHTTA, Bhartendu PANDEY, Laura HAMMETT (Cloud to Street), Gabriel PESTRE (Data-Pop Alliance) ORIGINAL LANGUAGE English ISSN 2492-2838 COPYRIGHT 1st quarter 2017 DISCLAIMER The analyses and conclusions in this document in no way reflect the views of the Agence Française de Développement or its supervisory bodies. All Technical Reports can be downloaded on AFD’s publications website: http://librairie.afd.fr 1 | TECHNICAL REPORT – N°24 – FEBRUARY 2017 Contents Contents AUTHORS ............................................................................................................................................................... 1 CONTENTS .............................................................................................................................................................. 2 ABSTRACT .............................................................................................................................................................. 4 1. INTRODUCTION – NEW THREATS, NEW INNOVATIONS, AND BRINGING NEW VULNERABILITY ANALYSIS TO SENEGAL ................................................................................................................................................................ 5 2A. BIOPHYSICAL RISK: BUILDING A HISTORICAL FLOOD DATABASE IN SENEGAL ................................................. 10 I. HISTORICAL FLOOD EVENTS ................................................................................................................................... 10 II. MAPPING HISTORICAL FLOOD EVENTS ..................................................................................................................... 12 III. FLOOD DETECTION METHODS ................................................................................................................................ 14 1. MODIS IMAGERY ................................................................................................................................................ 14 2. LANDSAT IMAGERY ............................................................................................................................................... 15 3. AUTOMATIC THRESHOLDING .................................................................................................................................. 15 4. UNOSAT DATA .................................................................................................................................................. 16 IV. FLOOD DETECTION RESULTS ................................................................................................................................... 17 1. DFO ALGORITHM IMPLEMENTATION ....................................................................................................................... 17 2. FEYISA ALGORITHM IMPLEMENTATION ..................................................................................................................... 18 V. FLOOD HISTORY IN SENEGAL .................................................................................................................................. 19 VI. LIMITATIONS ....................................................................................................................................................... 21 2A. BIOPHYSICAL RISK: DATA-DRIVEN HYDROLOGY WITH MACHINE LEARNING .................................................. 22 I. INTRODUCTION .................................................................................................................................................... 22 II. METHODS .......................................................................................................................................................... 23 1. STUDY AREAS ...................................................................................................................................................... 23 2. FLOOD CONDITIONING FACTORS ............................................................................................................................. 24 3. MODEL DEVELOPMENT ......................................................................................................................................... 24 4. PERFORMANCE METRICS ....................................................................................................................................... 25 III. RESULTS ............................................................................................................................................................. 26 1. SAINT-LOUIS PROTOTYPE ...................................................................................................................................... 26 2. PREDICTIONS FOR FLOOD-PRONE REGIONS ACROSS SENEGAL ....................................................................................... 27 IV. ERROR, MODEL LIMITATIONS, AND FURTHER RESEARCH .............................................................................................. 29 V. CONCLUSION ....................................................................................................................................................... 29 3. SOCIAL VULNERABILITY TO DISASTER IN SENEGAL ........................................................................................... 31 I. INTRODUCTION .................................................................................................................................................... 32 II. METHODS .......................................................................................................................................................... 34 1. DATA FOR SOCIAL INDICATORS ............................................................................................................................... 35 2. DEMOGRAPHIC PROFILE OF SENEGAL ....................................................................................................................... 36 3. SPATIAL HOTSPOTS OF KEY DIMENSIONS THAT AFFECT SOCIAL VULNERABILITY ................................................................. 37 4. VARIABLE SELECTION ............................................................................................................................................ 38 5. PCA-BASED FACTOR ANALYSIS ............................................................................................................................... 41 III. SOCIAL VULNERABILITY PROFILE OF SENEGAL ............................................................................................................. 45 2 | TECHNICAL REPORT – N°25 – FEBRUARY 2017 Contents IV. DATA LIMITATIONS ............................................................................................................................................... 47 V. RECOMMENDATIONS FOR APPLICATION AND FURTHER RESEARCH ................................................................................. 48 4. COMBINED SOCIO-PHYSICAL VULNERABILITY OF SENEGAL .............................................................................. 50 5. PARTICIPATORY ENGAGEMENT FOR FLOOD RESILIENCE: A BLUEPRINT FOR ENGAGING LOCAL SENEGALESE IN THIS ASSESSMENT ................................................................................................................................................ 51 I. INTRODUCTION .................................................................................................................................................... 52 II. PARTICIPATORY ENGAGEMENT FOR FLOOD RESILIENCE IN THE SENEGALESE CONTEXT ........................................................ 55 III. METHODOLOGY FOR PARTICIPATORY STAKEHOLDER ENGAGEMENT ............................................................................... 56 1. ON-LINE PARTICIPATORY DIGITAL FLOOD MAP VERIFICATION TOOL .............................................................................. 57 2. WORKSHOP SITE SELECTION................................................................................................................................... 57 3. IN-PERSON WORKSHOPS ....................................................................................................................................... 58 IV. NEXT STEPS AND FOLLOW UP ................................................................................................................................. 61 1. TRACKING SUCCESS .............................................................................................................................................. 61 2. OVERCOMING BARRIERS TO SUCCESS ....................................................................................................................... 62 CONCLUSIONS: NEXT STEPS.................................................................................................................................