A REVIEW OF THE ESTIMATIONS ON SEA LEVEL RISE FOR THE BAY OF BENGAL DUE TO CLIMATE CHANGE Fariba Halim Aurin 1* and A.K.M. Saiful Islam 2 1 Graduate student, Institute of Water and Flood Management, University of Engineering and Technology, Dhaka-1000,, e-mail: fariba432@gmail.com 2 Professor, Institute of Water and Flood Management, University of Engineering and Technology, Dhaka-1000,, e-mail: akmsaifulislam@iwfm.buet.ac.bd ABSTRACT Among the variables which depict the vulnerability of and its coastal zone to the impacts of climate change, the magnitude of sea level rise (SLR) is turning into the crucial one. As this area is the most prone to the impact of climate change and at the same time is a developing economic zone, an approximate measure of the level was highly demanded to proceed with implementing any sort of development project. The trend of sea level rise made from the climate models predicted a 59 cm rise in the coastal region in consequences of precipitation and temperature scenarios developed by IPCC. While 2D hydrodynamic models established using the primary data collected by the Water Development Board and several approximated data in absence of primary data estimates 10.3 percent of the coast land can get inundated by the year of 2050 due to sea level rise, analysis of satellite images from NOAA shows it will reach around 1meter by 2100. These dynamic data should be correlated to get an exact of this extreme event of SLR and hence take necessary measures to prevent and mitigate the coming situation to preserve the coast of Bay of Bengal. Keywords:, Bay of Bengal, climate change, coastal zone, sea level rise, deltas 1. INTRODUCTION is situated at the interface of 2 different environments, with the Bay of Bengal to the south and the Himalayas to the north which is an exceptional geography that causes not only lifegiving monsoons but also catastrophic ravages of natural disasters, to which now are added climate change and SLR (Ali, 1999). From the tide gauge data, the global average sea level rise was found to fluctuate between 0.1 to 0.2 meters in the 20 th century (IPCC, 2001b). The climate models, hydrographic observations, and satellite data are the sources of the assessments on sea level rises, which explains that the rise is not uniform around the world. While the rates are several times higher than the mean global rise in some region, it is falling in the other regions. There have been many studies carried out in the past that mentioned different figures of sea level rise in the coastal zone of. An in-depth study regarding the climate change and SLR on the coastal region of the country became essential. In absence of such study, an attempt has been taken to figure out the s of SLR in the deltaic areas of the Bay of Bengal due to the changes in climate based on the reviewing of the facts and figures of various studies. 631
2. METHODOLOGY Secondary data resources like IPCC reports, international reports, books, scientific journals, government policy documents has been used in this study to come up with the approximation. Both the qualitative and quantitative data and information were used to portray the scenario of SLR in the coast of. Measured SLR rate was the prime concern, while climate change was emphasized to be the responsible cause of SLR leading to coastal erosion. 3. RESULT 3.1 SLR in the Bay of Bengal Coastal Region An analysis in the NAPA found that SLR will increase up to 0.88meter by 2100 leading to increase the salinity level and move the salinity front about 60km north affecting the Tentulia River which is currently the only fresh water pocket in the estuary. Table1 presents predicted rise of sea level by the year 2100 in the Bay of Bengal by different organizations. Table1: Rise in Sea level by the year of 2100 in the Bay of Bengal by different organizations IPCC (AR4) level (m) experience the extremity 2007 0.59 2100 NAPA Coast of 2006 0.894 2100 World Bank 2000 1.00 2100 Woods Hole Oceanographic Institute 1986 2.00 2010 In 2007, the Intergovernmental Panel on Climate Change (IPCC) estimated that climate change would cause 0.6 meter or more of global sea level rise by 2100. The analysis of NAPA (National Adaptation Plan of Action) (cited in UNDP 2007) demonstrated 0.14 meter, 0.32 meter and 0.894 meter rises in the sea level of the coastal zone of by the year of 2030, 2050 and 2100 respectively. The assessments of World Bank projection show that last half of the present century (from 2050 to 2100) sea level will rise 0.75 meter. The level has been predicted to reach 1.5meter as in extreme scenario. Recent studies of IPCC suggested that the delta and island nations are at high risk of being the victim of sea level rise due to the ocean volume and thermal expansion. Assessments made from physical models used in Department of Environment (DoE) of, and relevant organizations have shown an increment in the sea level which are summarized for the year of 2050 in Table2 and 2100 in Table1. 632
Table2: Rise of Sea level within the year of 2050 in the Bay of Bengal by different organizations. World Bank level (meters) experience the extremity 2000 0.25 2050 Woods Hole Oceanographic Institute World Bank DOE NAPA NAPA Coast of Coast of 1986 0.13 2050 2000 0.10 2020 1993 0.3-1.5 2050 2006 0.14 2030 2006 0.32 2050 3.2 SLR in the Sunderbans Region Apart from the international and government organizations, individual and group attempt has been taken to assess the condition of extremity of sea level rise in the only deltaic region experiencing tidal effects the most. Table 3 presents predicted sea level rise in the Sundarban region by 2050 suggested by different studies. According to Prof. Hazra, about 15 per cent of the Indian Sundarbans region on the northern shore of the Bay of Bengal will be submerged by 2020. Table3: Rise in Sea level within the year of 2050 in the Bay of Bengal by different organizations. level (%) experience the extremity IWM Coastal land 2006 10.3% 2050 Professor Hazra Indian Sundarbans region of BOB 2010 15% 2020 There exists a continuous natural subsidence in the Sundarbans, in contrast with the estuaric sea level rise which caused a rate of sea level rise about 2.2 mm per year (Sanyal P. 2002) and thus the net rise comes at 3.1mm per year at the sea. Hydrodynamic 2D model of the Bay of Bengal was developed by IWM and updated, re-calibrated and verified Jakobsen et al. (2002) to adopt in several models. Historical tidal data magnitude have suggested the rate of SLR in several coastal measurement stations in to be of higher magnitude than the mean projected rate of global SLR. Out 633
of the 19 districts covering the coastal zone of, only 12 districts meet the sea or lower estuary directly. According to the study of SMRC (SAARC Meteorology Research Centre) Hiron Point, Char Changa, Chittagong and Cox s Bazar are expected to have a rate of increase in SLR of 4mm, 6mm, 7mm and 7.8mm per year respectively Table 4. Table 4: Trend of SLR along the coast of (SMRC-2001) Staion Name Trend (mm/year) Latitude (N) Longitude (E) Hiron point 4 21 48 89 28 Char Changa 6 22 08 91 06 Cox s Bazar 7.8 21 26 91 59 The rise of sea level will pose some adverse impact including amplified trends in the congestion of coastal drainage systems, reduction of fresh water availability in coastal communities, protective functions of coastal ecosystems and natural geomorphologic processes, and increased human and material losses in the wake of more intense cyclone and storm surges, and frequent flooding disasters. According to the case study of UNESCO stated that an anthropogenic 0.45-meter rise in sea level by the end of the 21 st century could wipe out 75% of the Sunderbans. 4. CONCLUSIONS This study reviewed and summarized the results of various studies for providing most up to date information on SLR of the Bay of Bengal. Though a huge investigation was made to estimate the global sea level rise, very few attempts has been taken to predict the same in the coastal region of. Being the only deltaic region having the most vulnerable coastal region, researchers should concentrate on the study of SLR using more precise data and modeling approaches. REFERENCES Colette, A., Rao, K., (2007). Case study on climate change and world heritage, UNESCO World Heritage Centre, Paris. IPCC (2001), Climate Change 2001: Working Group II: Impacts, Adaptation and Vulnerability, Section 11.3.2.4 IPCC (2007), WG1, The Physical Science Basis, Section 11.9.4 (Box 11.5) Sanyal, P. (2002), Sea-Level Rise and Sundarban Mangrove, in G. Quadros, (ed), Proceedings of the National Seminar on Creeks, Estuaries and Mangroves Pollution and Conservation, 28-30 November 2002, Thane, India, pp. 47-50. SMRC (2003). The Vulnerability Assessment of the SAARC Coastal Region due to Sea Level Rise: Case. SAARC Meteorological Research Center, Dhaka SMRC-No. 3 IWM (2005). Impact assessment of climate change on the coastal zone of. Final Report, Institute of Water Modelling, Dhaka,, 37p. Alam, M. (2003). Country Case Study, National Adaptation Programme of Action (NAPA) Workshop, 9 11 September 2003, Bhutan. DOE (1993) Assessment of the Vulnerability of Coastal Areas to Sea Level Rise and Other Effects of Global Climate Change, Pilot Study. Department of Environment, Government of. 634
Karim, M. F. and Mimura, N. (2010), Sea level rise in the Bay of Bengal: its impacts and adaptations in, center for water environment studies, Ibaraki University, Hitachi, Ibaraki 316-8511, Japan Church, J. A., White, N.J., Thorkild, A., Wilson, W.S., Woodworth, P.L., Dominigues, C.M., Hunter, J.R. and Lambeck, K (2008). Understanding global sea levels: past, present and future, Sustainable Science, vol. 3 pp. 9 22 World Bank (2000). climate change and Sustainable Development. Report No. 21104- BD NAPA, cited in UNDP, (2007). Human Development Report-2007/08 Jakobsen, F., Azam, M. H. and Kabir, M.U. (2002) Residual flow in the Meghna Estuary on the coastline of. Estuarine, Coastal and Shelf Science 55, 587-597 Olesen, K. W., Ammentorp, H.C., and Petersen, N. H., Mega deltas and the climate change challenges, Denmark. Hossain, Md. L., Hossain, M. K., climate change, sea level rise and coastal vulnerabilities of with adaptation options. Sarwar, G. M., Khan, M. H. (2007) Sea Level Rise: A Threat to the Coast of, Internationales Asienforum, Vol. 38, No. 3 4, pp. 375 397 Karim, M. F., Mimura, N (2008), Impacts of climate change and sea-level rise on cyclonic storm surge floods in, Global Environmental Change 18, pp. 490 500 Ali, A. (1999), Climate change impacts and adaptation assessment in, CLIMATE RESEARCH, SPARRSO, Vol. 12: 109 116. 635