Analysis of Geo-environmental Indicators for Coastal Zone Management of East Coast of the Bay of Bengal along Bangladesh

Abstract

The present study area, the east coast of Bangladesh, stretched along the Bay of Bengal is characterized with unique geo-environment and biodiversity. The coastal zone, endowed with a rich pool of diverse, complex and dynamic Terrestrial and Coastal & Marine Ecosystem, has been increasingly confronting with the deteriorating geo-environment owing to escalating unscrupulous anthropogenic interventions. Consequences were observed in the changes of geomorphic features, such as shoreline movement, deterioration of environmental quality of soil and water, as well as changes or loss in terrestrial and coastal and marine biodiversity. The consequent geo-environmental degradation such as, the extremely polluted river estuaries, rapid shoreline change, as well as the declaration of the Teknaf coast, Cox‟s Bazar district as the „Ecologically Critical Area (ECA)‟ by the Government of Bangladesh in 1999 enthused to select the eastern coastal zone, starting from the Feni River up to Inani beach, Teknaf coast as the study area of the present research. A research gap regarding an integrated study about the „Cause and Effect‟ relationship between the geo-environmental state and anthropogenic activities were revealed from the previous literatures. Hence, the main theme of the study was to analyze the selected geo-environmental features as study indicators and to incorporate them into the existing ICZMP (1999) and future development plans and policies. Accordingly the study attempted to develop a Strategic Policy Framework (SPF) to incorporate the present study geo-environmental indicators into the existing ICZMP (1999) of Bangladesh, as well as into the future development plans like- the Sustainable Development Goals (SDGs, 2015-2030), 7th and 8th Five Year Plans (FYP, 2016-2020 and FYP 2021-2025), Bangladesh Delta Plan, 2100, and into the UNESCO‟s Ocean Science Decade (2021-2030) declaration. The main theme and objectives of the study were to analyze the state of selected geo-environmental indicators of the east coast to provide them as development indicators for existing and future Coastal Zone Management (CZM) plans and policies for the east coast. Soil, water and mollusk shell samples were collected, processed, measured and analyzed to reveal the geo-environmental state of the study area. The „Net Shoreline Movement‟ (NSM) of the sample area coastlines was measured; heavy metal concentration and physio-chemical quality of soil and water samples from the point sources of pollution along the study area were measured. Further, floral and faunal bio-diversity changes of the study area were explored by measuring two parameters, such as the „Vegetation Coverage‟, and concentration of five heavy metals and CaCO3 in the mollusk shells. Maps were created from six radiomterically corrected Temporal Landsat Images with ArcGIS to illustrate the location of the study area and sample areas, the chronological shoreline movement pattern and the vegetation coverage depletion pattern of the sample areas. To reveal the geomorphic condition of the study area, the „Shoreline Extraction and Accuracy Assessment‟ method was used to achieve a comparative assessment of the coastline or shoreline movement along east coast, within a time span of twenty five years (1990 to 2015). The „Digital Shoreline Analysis System (DSAS)‟ was applied upon the sample area coastlines to get the previous shoreline positions (1990-2015). The „Modified Normalized Difference Water Index (MNDWI)‟ and „Single Operator‟ methods were applied to extract the „Land-Water boundary‟ from the satellite images. Transect lines were created perpendicular to user-defined „Base Line‟ to calculate the „Net Shoreline Movement (NSM)‟. The EPR graphs and NSM map revealed that, the shorelines of the Feni River and the Bakkhali River estuaries, and the shoreline of the Marine drive sample area have experienced noteworthy changes during the study time (1990 to 2015). However, the field survey (March, 2018) accentuated that, the Feni River estuary has become accretion dominated, after the completion of the Muhuri Closure Dam (MCD) upon the Feni River. The decreased tidal force at downstream of the closure dam, huge logging along the shores and deposition of massive amount of silts, carried down through the vast Ganges-Brahmaputra-Jamuna River system are the major causes of accretion. The Jalkadar khal was comparatively stable as the shorelines were protected by the coastal protection dams on both sides. However, the huge garbage disposal from the fish market, boat construction and repairing factories, ice factories were observed to narrow down the estuary width. The EPR graphs and NSM map of the Bakkhali River estuary sowed that, the river estuary became erosion prone due to strong waves created by the frequently commuting passenger speed boats, and the big fishing trawlers since 2016. However, converse situation was observed in 2018 while huge accretion was observed at both shores of the estuary mouth. For instance, the Kasturi ghat and Nuniarchara fishery ghat area were going under land reclamation process for the extension of Cox‟s Bazar Airport, construction of Fishing Community Rehabilitation project, and Khurushkul Bridge by dumping huge amount of municipal wastes and river sediment carried down from the Meghna River. On the other hand, the EPR graphs and NSM map of the Teknaf coast along Marine drive (1990 to 1995) depicted massive erosion process. The coastline along Himchari and Sonarpara has eroded and moved east wards, almost near the Marine drive. Though the time span from 2010 to 2015 illustrated complete erosion activities along the entire study area, the field survey during March 2018 observed a gradual siltation process occurring within the geo-sand bag and cemented tetra- pod protected areas. The environmental condition of the sample areas was assessed by measuring the concentration of five heavy metals, two non-metals or nutrients and four physio-chemical parameters of the soil and water. The concentration of Fe was the highest followed by the concentration of Pb, which were alarmingly higher than the world average in most of the soil and water samples. The untreated industrial wastes and huge municipal garbage were detected as the main point sources of pollution. During the field survey in 2018, the eastern side of the Bakkhali River sample area was observed to be filled up with huge municipal garbage to construct the Khurushkul Bridge, allowing seepage of toxic effluents from these wastes to contaminate the soil and water of the study area. Further, the heavy metal concentration of sample mollusk shells was measured to examine the adverse effect of them upon the faunal bio-diversity. Added to these, the CaCO3 content of the sample mollusk shells depicted a declining concentration (42.5% - 91%) of CaCO3 in comparison to the world standard content (95% - 97%). The Normalized Difference Vegetation Index (NDVI) and vegetation coverage maps were prepared to assess the vegetation depletion at the sample areas. The study showed that, vegetation coverage at Bakkhali river estuary reached a negative scale (- 0.1). Recognizing the deteriorating geo-environmental state of the study area, the present study attempted to develop a policy framework for sustainable management plan. A Pressure-State-Response (P-S-R) model was formulated basing upon the findings of the present study to portray the „Cause and Effect‟ relationship among the present study indicators. In the P-S-R index, the Pressure indicators (industrial effluents, municipality wastes, and illegal encroachment, construction of river dams and coastal embankments, and rapid deforestation) exert negative impacts upon the study area. The Response indicators (Local and national stakeholders, Government plans and policy frameworks) were observed to play a partially functional role in confronting, mitigating, as well as, developing the coast in a sustainable approach. Basing upon the present study P-S-R model, incorporation of a SPF for CZM was attempted. The recommendations of the concerned stakeholders, like-the Cyclone Preparedness Programme (CPP) and Forest Divisions of Chattogram and Cox‟s Bazar; the Fisheries Research Institute, Cox‟s Bazar; the BWDB, Chattogram, Upazila Chairman and local journalists were included into the framework. Finally, the present study advocates to create a strong integration among all the local stakeholders, as well as to incorporate the proposed SPF for the fully-functional implementation of the existing ICZMP, along with the future coastal zone management plans and policies to form a sustainable coastal zone in Bangladesh.