The Case Study of Sandwip Island
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Università degli Studi di Ferrara DOTTORATO DI RICERCA IN Scienze della Terra CICLO XXVII COORDINATORE: Prof. Massimo Coltorti Geomorphological Evolution and Vulnerability of Low- Lying Coasts in Bangladesh: The Case Study of Sandwip Island Settore Scientifico Disciplinare GEO/04 Dottorando Tutore Mohammad Muslem Uddin Prof. Ciavola Paolo, PhD Anni 2012/2014 March‘2015 ii DEDICATION For my beloved Mother (Mohsena Khaatun), without whose love, blessings and care, I would not be where I am today. For my beloved Father (Late Md Obaidul Hoque), who taught me ―always keep busy working with something, even whe there‘s nothing to do‖. For my beloved elder Brothers (Mr Shahid Ullah & Mohammad Mowla), who have always taught me how to love and take care of youngers, without whose love and support, my education would have never been possible. For my two most respected late Professors (Dr. Nuruddin Mahmud & Dr. Mohammad Zafar) and ex Professor (Dr. Nani Gopal Das) of the Institute of Marine Sciences and Fisheries, University of Chittagong, who have always taught me to never give up with my research and further education. Finally, to my respected mentor, Professor Dr. Paolo Ciavola, without his help and continuous guidance, this would have never been possible. iii ORIGINALITY STATEMENT ‗I hearby declare that this submission is my own work and to the best of my knowledge, it contains no materials previously published or written by another person for the award of any other degree at UNIFE or anyother educational institute, except where due acknowledgement is made in this thesis. Any contribution made to the research by others, with whome I have worked at UNIFE or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this work is the compilation of my own works, except to the extent that cooperate from others in the project design or in style, field works, presentation and linguistic expression is duly acknowledged.‘ Signed Date iv PREFACE Most coastal areas are highly fragile, as they are constantly subjected to high physical energy imparted by varying degrees of wave, tide and current activities. Coastal areas like those in Bangladesh have been in more concern for their alarming huge and quick geomorphodynamic changes due to some more hydrometeorological effects like floods, cyclones and erosions etc. Increasing climate change induced vulnerability like Sea Level Rise (SLR) has been making the situation worse day by day. In order to properly interpret the hazardous mechanisms to set up a time demanding management and precautionary system towards reducing the vurnability to disasters, there is a need for a thorough understanding of the geomorphological evolution, hydro- meteorological setting, socio-economical and ecological status of the target area. Community perception and indigenous coping strategies are a well accepted approach worldwide for adaptation to climate induced disasters. This particular study involves a comprehensive approach to understanding the situations making the erosion and storm surge prone Sandwip Island one of the most risky places to live. The first chapter introduces the work structure, study background, objectives and motivation of the work while chapter two briefs on the study area geography, geo-morphology, socio-cultural and socio-ecological characteristics. A brief historical flash back and hydrodynamics around the island form part of this chapter.The materials and methods used in the research works are briefly described in chapter three. In the chapters four and five, the results are summarized and the outcomes are discussed which ultimately aim at the objective of the project. Chapter four is composed of the results and discussion on the geomorphological, land use pattern changes and tidal variation status while the risk assessment by public perception and the copying strategies practices in the community are enclosed in chapter five. Finally, the conclusive remarks are outlined in the sixth chapter with useful recommendations for further use of the results. The last chapter deals with the references of the extensive literature review on the studies, reports and documents which were found to be helpful to develop the project, to enrich the understanding of the works, to verify the results, to get useful information and also to follow the methods used during the mission. v In connection with the thesis, the following research papers have been published in the respective conference proceedings after presentation in international meetings: Uddin, M.M. & Ciavola, P. 2012. Geomorphological Evaluation and Coastal Changes of Sandwip Island, Eastern GBM Delta, Bangladesh. Conference Proceedings: ITALY- CINA: AN ANCIENT CULTURAL HERITAGE AND THE CHALLENGE FOR FUTURE DEVELOPMENT, Bologna, Italy, 22 - 23 October 2012 (ISBN 978-88- 6155-515-0), p181-188. Uddin, M.M. & Ciavola, P. 2013. Sediment characteristics and Coastline Change of a Low- lying Island (Sandwip) in the Eastern GBM Delta, Bangladesh. Proceedings of ANDROID Residential Doctoral School Work Package III, Limassol, Cyprus, 23-24 October 2013 (ISBN 978-1-907842-52-8), p56-65. Ciavola, P., Uddin, M.M., Duo, E., Lee, B. and Fakhruddin, S.H.M., 2015 (Accepted). Vulnerability of Bangladesh Coastline to Inundation under Cyclone Activity: Past Records and DRR Strategies at Sandwip Island. E-proceedings of the 36th IAHR World Congress, 28 June – 3 July, 2015, The Hague, the Netherlands. vi ABSTRACT (ENGLISH) Bangladesh is ranked as the ―5th most at-risk country‖ in the world in terms of disasters with a world risk index of 20.22% in the World Risk Report 2012. Coast and island flooding induced by extreme storms and cyclones born in the Northern Indian Ocean passing through the funnel shaped shallow northern Bay of Bengal are the most dangerous natural hazards in the area. Additionally, remarkable geomorphological change of the lower GBM active delta and relative Sea Level Rise (SLR) have drawn special attention to the environmental scientists and respective managers for the alarming more intense and more frequent upcoming climate change vulnerabilities. The Lower Meghna River Estuary (LMRE) is an extremely dynamic estuarine system with dramatic geomorphological changes of the offshore islands. The erosion and accretion rates are remarkably high and the islands are reducing their original size. As populations flock to the coast and offshore islands at threat from erosions, storm inundation and sea level rise, intensive studies must be carried out on the vulnerability of these coastal regions. Sandwip Island, located at the confluence of the Lower Meghna River Estuary, shaped and characterized by both tidal actions of the Bay of Bengal and river streams of the Meghna, was chosen as the only international case study site outside Europe in the framework of the Risc-KIT FP7 European project (http://www.risckit.eu/). The project aims to develop tools and methods to reduce risk and increase resilience of coastal areas. The toolkit will be implemented for each case study. The present works aims to describe the state of the art of knowledge on the island covering geomorphology, sediment characteristics, hydrodynamics and socioeconomics. Community perceptions and indigenous coping strategies aspects of the island are included in a coastal vulnerability perspective to be useful in further research, development of effective preparedness, management and actions plan. To reach this goal, an attempt was taken to find out the answers to the following questions: 1) What is the status of geomorphological changes? 2) What are the sediment characteristics of the erosion-accretion prone shorelines? 3) What is the status of the sea level rise relative to the island 4) What is the total vulnerability/hazard ranking by local perceptions? 5) How much has the land use changed due to erosion and associated hazards ? and finally 6) What strategic changes should be taken? The research questions were answered using topographic surveys, lab based sediment analysis, tide gauge data analysis, erosion-accretion mapping and development of high resolution DEM and TIN vii using Remote Sensing and GIS-based tools and techniques and questionnaire survey results interpreted with national disaster management plans. The study found that the island is more physically prone to coastal erosion, coupling with storm surges and sea level rise making it more vulnerable in future. The erosion rate considering both shoreline and area changes is much more intense exceeding accretion in the silty clay sedimentary parts and the sea level rise trend is alarming in comparison with other nearby coastal areas in Bangladesh. Tidal data analysis for Sandwip shows semi-diurnal components higher in amplitude than Chittagong. Diurnal amplitudes are comparable and phases are generally higher for Sandwip with a 47 minute delay than Chittagong. The DEM demands more intensive bathymetric information that should be used for more accurate hydrometeorological models for the low elevated island, where as the island is almost flat with the average topography is only 5 meter above MSL and the north-western part is slightly higher than the south-western part as observed in the TIN justified by Topographic survey. The physical assets have been declining stressing on the socioeconomy of the community as found by the social survey as well as land use satellite mapping. So, a relatively high earthen embankment encircling the island, a crossdam connecting north side of the island to mainland