EU EDF – SOPAC Project Report 69g Reducing Vulnerability of Pacific ACP States SAMOA TECHNICAL REPORT – ECONOMIC ANALYSIS OF FLOOD RISK REDUCTION MEASURES FOR THE LOWER VAISIGANO CATCHMENT AREA February 2008 Prepared by: Allison Woodruff EU-EDF Reducing Vulnerability of Pacific ACP States Samoa – Economic analysis of Flood Risk Reduction Measures, Lower Vaisigano – 2 ACKNOWLEDGEMENTS This research was conducted with the invaluable support of Assistant Chief Executive Officers of the Ministry of Natural Resources and Environment (MNRE) Mr Mulipola Ausetalia Titimaea, Meteorology Division; Mr Suluimalo Amataga Penaia, Water Resources Division; and Mr Tagaloa Jude Kohlhase, Planning Urban Management Agency. Thanks also go to Sala Sagato Tuiafiso, Principal Scientific Officer and Filomena Nelson, Principal Disaster Management Officer for their valuable input into this study. The author would also like to thank Garry Martin at Fletcher Construction and John Tagiilima at OSM Consultants for providing the critical data and information necessary for producing this report. Thanks to Siosina Lui, EDF 8 Country Intern, for coordinating the in-country visit to Samoa and for the invaluable assistance provided while conducting household and business surveys. Thanks also to the staff at the MNRE and students at the National University of Samoa who helped to gather important data for this study through business and household surveys. Neta Pelesikoti at the Pacific Islands Applied Geoscience Commission (SOPAC) provided assistance in carrying out the household and business surveys and training the survey team while Litea Buikoto and Michael Bonte-Grapetin at SOPAC provided flood maps and other information which was essential for carrying out the research required for this report. The author is grateful to Paula Holland and James Dalton at SOPAC, and Darren Lumbroso at HR Wallingford for reviewing the study and providing valuable input. Further acknowledgement to other stakeholders from the private sector, NGOs and relevant national donor funded projects for providing input and ideas for this study. Important Notice This report has been produced with the financial assistance of the European Community; however, the views expressed herein must never be taken to reflect the official opinion of the European Community. [EU-SOPAC Project Report 69g – Woodruff] EU-EDF Reducing Vulnerability of Pacific ACP States Samoa – Economic analysis of Flood Risk Reduction Measures, Lower Vaisigano – 3 TABLE OF CONTENTS Acknowledgements...............................................................................................................................................................................2 EXECUTIVE SUMMARY ......................................................................................................................................................................7 1. Introduction .......................................................................................................................................................................................8 1.1 European Development Fund project Reducing vulnerability in Pacific ACP states...............................................................8 1.2 Objective of study..................................................................................................................................................................10 1.3 Background Samoa...............................................................................................................................................................10 1.4 Flooding in Apia ....................................................................................................................................................................11 1.5 The Study Area: Lower Vaisigano Catchment Area..............................................................................................................11 1.6 Other Flood Management Projects in Apia ...........................................................................................................................13 2. Methodology: Economic Analysis ...................................................................................................................................................13 2.1 Purpose of an Economic Analysis.........................................................................................................................................13 2.2 Benefit-cost analysis procedure:...........................................................................................................................................13 2.3 Time span of the economic analysis .....................................................................................................................................16 2.4 Scope of Analysis..................................................................................................................................................................16 3. Impact of Flooding in the Lower Vaisigano Catchment Area ..........................................................................................................16 3.1 Vulnerability: population and infrastructure at risk from flooding...........................................................................................16 3.2 Flood Hazard Maps...............................................................................................................................................................18 3.3 Impact of Past Flood Events .................................................................................................................................................18 3.4 Household and Business Survey ..........................................................................................................................................19 3.5 Estimated economic impact of flooding.................................................................................................................................20 3.5.1 Household Losses:.................................................................................................................................................22 3.5.1.1 Structural Damage to Homes ..................................................................................................................22 3.5.1.2 Damage to Household Contents .............................................................................................................24 3.5.1.3 Household clean-up costs .......................................................................................................................26 3.5.1.4 Lost household income............................................................................................................................27 3.5.2 Commercial Losses................................................................................................................................................28 3.5.2.1 Estimated damage to structure and contents of businesses...................................................................28 3.5.2.2 Business clean-up costs..........................................................................................................................29 3.5.2.3 Lost business revenues...........................................................................................................................29 3.5.3 Infrastructure Losses..............................................................................................................................................30 3.5.4 Social Sector Losses: Damage to Schools and Churches.....................................................................................31 3.5.5 Total estimated flood losses for all sectors ............................................................................................................31 3.5.5.1 Annual average flood damages...............................................................................................................32 4. Economic Analysis of Selected Structural Flood Management Options .........................................................................................33 4.1 Flood Embankments/walls ....................................................................................................................................................33 4.1.1 Location and design of flood embankments...........................................................................................................33 4.1.2 Costs flood walls/embankments.............................................................................................................................34 4.1.3 Benefits of Flood Walls/Embankments...................................................................................................................35 4.1.5 Economic pay-off from investing in floods walls embankments .............................................................................36 4.1.6. Constraints to building flood walls/embankments .................................................................................................36 4. 2 Construction of by-pass/diversion channel...........................................................................................................................37 4.2.1 Proposed design for by-pass/diversion channel.....................................................................................................37 4.2.2 Costs of constructing diversion