Southwest Bangladesh Research Articles

Process Controls of the Live Root Zone and Carbon Sequestration Capacity of the Sundarbans Mangrove Forest, Bangladesh

The conservation of coastal wetland ecosystems, like mangrove forests and salt marshes, represents a critical strategy for mitigating atmospheric emissions and climate change in the 21st century. Yet the existence of these environments is threatened by human-induced disturbances, namely deforestation and accelerated sea-level rise. Coastal systems maintain surface elevation in response to sea-level rise through a combination of physical and biological processes both above and below the ground surface. The quantification and relative contribution of belowground process controls (e.g., seasonal water content, organic matter decomposition) on surface elevation change is largely unexplored but crucial for informing coastal ecosystem sustainability. To address this knowledge deficit, we integrated measurements of surface elevation change of the live root zone (0.5 to 1 m depth) with geotechnical data from co-located sediment cores in the Sundarbans mangrove forest (SMF) of southwest Bangladesh. Core data reveal that the primary belowground controls on surface elevation change include seasonal fluctuations in pore-water content and the relative abundance of fine-grained sediments capable of volumetric expansion and contraction, supporting an elevation gain of ~2.42 ± 0.26 cm yr−1. In contrast to many mangrove environments, the soils of the SMF contain little organic matter and are dominantly composed (>90%) of inorganic clastic sediments. The mineral-rich soil texture likely leads to less compaction-induced subsidence as compared to organic-rich substrates and facilitates surface equilibrium in response to sea level rise. Despite a relatively high soil bulk density, soil carbon (C) density of the SMF is very low owing to the dearth of preserved organic content. However, rates of C accumulation are balanced out by locally high accretion rates, rendering the SMF a greater sink of terrestrial C than the worldwide mangrove average. The findings of this study demonstrate that C accumulation in the SMF, and possibly other alluvial mangrove forests, is highly dependent on the continued delivery of sediment to the mangrove platform and associated settings.

Enhancing effectiveness of tidal river management in southwest Bangladesh polders by improving sedimentation and shortening inundation time

Bangladesh, one of the countries most vulnerable to climate change, is threatened by sea level rise (SLR) and land subsidence. The tidal river management (TRM) practised in coastal regions of Bangladesh has the potential to raise the land by sedimentation, to counteract SLR and subsidence. TRM is an indigenous method in which dikes are breached to readmit sediment-rich water into a polder, which results in sediment being deposited in depressions in the polder called ‘beels’, while simultaneously preventing silting-up of the tidal rivers. However, after several years of continuous sedimentation from TRM, deposition has been uneven and less than expected.To study the effectiveness of TRM, this research analyses different scenarios to identify which operation schemes most effectively trap sediment to raise the land surface. The scenarios developed considered the number of inlets, flow regulation through the beel using open inlets or gated inlets with different operation schemes, and seasonality. The study area was Pakhimara Beel in southwest Bangladesh, where TRM is ongoing. To simulate the scenarios, a two-dimensional (2D) morphodynamic model with variable cell size was set up, calibrated and used. The simulation results were analysed for total sediment deposition, uniformity of spatial distribution of sediment deposition and trapping efficiency.Sediment deposition shows clear seasonal variability, with greatest deposition in the pre-monsoon period, less during monsoon and least in the dry season. Greatest deposition combined with high spatial uniformity was found for TRM that uses two inlets located at opposite sides connected to different watercourses. Regulated flow using successively opened gates resulted in highest sediment deposition in all seasons, about double that of the existing situation without gate. However, given the complexity and cost of gate operation, TRM with two inlets located at opposite sides of the beel without flow regulation may be considered more feasible, and still effective despite 20–30% less sediment deposition. To also increase acceptability by local affected stakeholders we propose to restrict this improved TRM to the monsoon period, to allow crops to be grown on the land in the dry and pre-monsoon periods, and ensure salinity is minimized. Such well-planned TRM has the potential to also counteract sea level rise in sinking deltas elsewhere in the world by enhancing sedimentation.

Effect of voluntary cooperativisation on livelihood capital of smallholder dairy farmers in the southwest of Bangladesh

This study investigated the effects of voluntary cooperativisationas conducted by the Community-Based Dairy Veterinary Foundation (CDVF) on the livelihood capital of smallholder dairy farmers. An essential part of this cooperativisation was the provision of community-based paid extension service to the farmers by the cooperative. The sustainable livelihood approach was used to analyse livelihood capital. A simple random sampling technique was used to gather data from 255 respondents: including 15key informant interviews, 5 focus group discussions and 5 case studies. Almost all of the farmers felt that the paid service was profitable. Equal portion of farmers realised moderate (49.80%) and high gains (50.20%) from CDVF. Most significant improvements occurred in physical, financial and human capital resources. CDVF has increased production, and improved farmer-to-market linkage maximised profit and income. Farmers reinvested their improved income in physical assets development. Farmers gained considerable knowledge, skill, employment, voice, intensified social networks, green homesteads and livelihood security from the CDVF services. The complementary effect of all five forms of livelihood capital strengthened the assets pentagon of the participating farmers. Regression results affirm that gender, education, distance from CDVF centre, amount of extension communication, increased milk production and higher income are the determinants of farmers’ improved assets base. CDVF needs to professionalise its management and corporate strategy, and their successful voluntary cooperativisation model needs to be promoted and encouraged by all including the State.

Socio-economic determinants of off-season summer tomato cultivation

ABSTRACT Off-season summer tomato (Solanum lycopersicum L.) cultivation in the tropics can return economic benefits to farmers. The study was undertaken to identify determinants of off-season tomato cultivation employing a double hurdle regression model. A total of 250 farmers from south-west Bangladesh were interviewed during November–December 2018. Initial adoption decision was positively influenced by higher levels of education, number of days in training, and income, while the level of adoption was influenced by availability of adult family member, access to formal credit, and income. Diversifying household income sources and improving access to financial institutions could increase the adoption level of off-season summer tomato.

Integrated Value Chain Development: Evidence from Bangladesh

Agricultural productivity and farmer welfare in developing countries is constrained by a multitude of market imperfections. Value chain development (VCD) is receiving much attention as a market-based policy instrument that can potentially address multiple of these constraints simultaneously. This paper provides a conceptualization of VCD and discusses how VCD can be used as a policy instrument. As an illustration, the paper describes the VCD project “SAFAL,” which uses an integrated approach to directly intervene in aquaculture, horticulture, and dairy value chains in South-West Bangladesh. The strategy is to first identify a demand downstream in the value chain and then to identify and reduce the constraints experienced by value chain actors upstream to meet this demand. Using a matched difference-in-difference methodology, this paper estimates farm household participation in SAFAL increases farm income and shortens the hungry season.

Water Logging in South-Western Coastal Region of Bangladesh: Causes and Consequences and People’s Response

Aim: Since decades, a major part of south-western coastal region of Bangladesh is being affected by water logging – a problem related to climate change along with some manmade activities. Therefore, the study was conducted to assess the causes and consequences of this problem and highlights the responses of affected people to attract policy planners’ intention for taking proper intervention.
 Place and Duration of Study: The study was conducted in the Laboratory of Plant Ecology, Department of Crop Botany, Bangladesh Agricultural University, Mymensingh, Bangladesh.
 Methodology: Qualitative and quantitative techniques have been applied to collect and analyze both the primary and secondary sources of data from various waterlogged areas of south west Bangladesh.
 Results: There is no single or a few factors are responsible for creating water-logging problem rather it is a combination of several factors and their cumulative effects over time. It is revealed from the analysis of primary and secondary sources of information that death of Mathavanga River in the 20th century, execution of Coastal Embankment Project since 1960’s, withdrawing water flow to the Padma River through operating the Farakka barrage after independent of Bangladesh, improper management of rivers, faulty land-use by influential people in the areas, monsoon downpour etc are major causes of the problem. The silted up river systems in area could not drain monsoon rain that occurred even for a couple of days. The consequences brought to inundate hundred thousand hectares of cultivable land unsuitable for crop production. More than one million people are directly affected in the areas and the number is gradually increasing over the years. Water stagnancy around the settlement areas remains 6 to 9 months in a year and many places became permanently waterlogged. The affected people have no other way out but to live with water. The congested water is polluted with salinity, chemical effluents with heavy metals, household debris’s and related other pollutants. Source of safe drinking water is destroyed. Therefore incidences of waterborne and skin diseases are increased. People are living with greatest inhumanity as food, shelter, sanitation, communications, educations and other prime needs are tremendously challenged. Many people lost their occupations and became destitute, some altered their livelihood to much lower grades, and many of them are forced to migrate to city areas. The marooned people demanded to the authority to declare their places as an affected area and sought the government intervention to bring an end to the crisis through operating the Tidal River Management plan and excavating or re-excavating of associated rivers, channels and rivulets.
 Conclusion: The authority need to pay keen attention to the issue and should take proper initiative to mitigate the water-logging problem permanently to save people living in the south western coastal region of Bangladesh.

Process Controls of the Live Root Zone and Carbon Sequestration Capacity of the Sundarbans Mangrove Forest, Bangladesh

The conservation of coastal wetland ecosystems, like mangrove forests and salt marshes, represents a critical strategy for mitigating atmospheric emissions and climate change in the 21st century. Yet the existence of these environments is threatened by human-induced disturbances, namely deforestation and accelerated sea-level rise. Coastal systems maintain surface elevation in response to sea-level rise through a combination of physical and biological processes both above and below the ground surface. The quantification and relative contribution of belowground process controls (e.g., seasonal water content, organic matter decomposition) on surface elevation change is largely unexplored but crucial for informing coastal ecosystem sustainability. To address this knowledge deficit, we integrated measurements of surface elevation change of the live root zone (0.5 to 1 m depth) with geotechnical data from co-located sediment cores in the Sundarbans mangrove forest (SMF) of southwest Bangladesh. Core data reveal that the primary belowground controls on surface elevation change include seasonal fluctuations in pore-water content and the relative abundance of fine-grained sediments capable of volumetric expansion and contraction. In contrast to many mangrove environments, the soils of the SMF contain little organic matter and are dominantly composed (>90%) of inorganic clastic sediments. The mineral-rich soil texture likely leads to less compaction-induced subsidence as compared to organic-rich substrates and facilitates surface equilibrium in response to sea level rise. Despite a relatively high soil bulk density, soil carbon (C) density of the SMF is very low owing to the dearth of preserved organic content. However, rates of C accumulation are balanced out by locally high accretion rates, rendering the SMF a greater sink of terrestrial C than the worldwide mangrove average. The findings of this study demonstrate that C accumulation in the SMF, and possibly other alluvial mangrove forests, is highly dependent on the continued delivery of sediment to the mangrove platform and associated settings.

Freedom of choice to migrate: adaptation to climate change in Bangladesh

ABSTRACT Adaptation is an essential part of climate change policy. In areas where impacts are likely to be severe, migration is considered to be an adaptation option. In Bangladesh coastal areas migration due to climate change is contingent on people’s freedom of choice at individual and household level. Following Amartya Sen’s capability approach, we argue that there should be a line drawn between migrations by free choice versus forced migration. Sen’s capability approach focuses on the importance of people’s freedom of choice to act, and the ability to achieve what they consider valuable in their life. In this paper, we use an extensive empirical work engaging 22 focus groups discussions (8–12 individuals in each group) and 14 Key Informants Interviews in South-West Bangladesh to elicit how freedom of choice changes with the economic class and social status of an individual. Using these data we apply Sen’s capability approach to understand the role of the freedom of choice when considering migration as an adaptation option. We argue that the capability approach is essential in revealing a thin border between migration as a (planned) adaptation option and forced migration.

A sequential assessment of WSD risk factors of shrimp farming in Bangladesh: Looking for a sustainable farming system

White Spot Disease (WSD) caused by White Spot Syndrome Virus (WSSV), is responsible for widespread mortality and economic losses across almost the entire Asian shrimp farming industry. The distribution of disease prevalence is however uneven, and is likely dependent on a range of management, environmental and socio-ecological factors. In this study, 233 farms were surveyed in southwest Bangladesh, the main shrimp farming zone, to produce a dataset from a range of pond types, culture techniques and farming practices. Four categories of data (site/farm characteristics, environmental variables, disease history, and management variables) with associated risk factors were selected following the development of a conceptual framework and a participatory rural appraisal tool. Factors potentially contributing to WSD prevalence in the current shrimp crop were first screened using univariate analysis and subsequently analyzed using a multivariate logistic regression to highlight significant risk factors. Association of the selected factors with WSD prevalence was examined using multivariate stepwise removal. The multivariate analysis revealed that farms operated by a tenant worker (p: 0.03), mixed use of fertilizer (p: 0.009), poor quality water source (p: 0.001), lack of reservoir for water purification (p: < 0.001), and frequent exchange of water during a single crop culture (p: < 0.001) were significantly associated with WSD prevalence. The results suggest that, where possible, better farm management practices including improving water quality, controlling water exchange and/or maintaining constant salinity, will reduce WSD prevalence.

Productivity growth and efficiency changes in prawn-carp–rice farming in ‘Gher’ system in Bangladesh: A Färe-Primont index approach

‘Gher’ farming system refers to the joint operation of three enterprises: freshwater prawn, carp and HYV rice practiced widely in the southwestern coastal Bangladesh. The paper estimates growth in total factor productivity (TFP) and its six finer components (technical change, technical, scale and mix efficiency changes, residual-scale and residual-mix efficiency changes) of the prawn-carp-rice joint culture and identifies their determinants by exploring a panel database of a cohort of 90 ‘gher’ farms over a 13-year timespan (2002–14) from southwest Bangladesh. The aim is to judge sustainability of this unique farming system. Results revealed that TFP grew @ 0.86% p.a. mainly powered by technical change @ 0.54% p.a. and mix-efficiency change @0.06% p.a. while technical and scale efficiency changes declined @ 0.17% and 0.10% p.a., respectively. Farm-level socio-economic factors exerted differential impacts on TFP growth and its components. The key conclusion is that the ‘prawn-carp-rice’ joint culture in ‘gher’ system is sustainable and has the potential to support growth of the broader agricultural sector and the Bangladesh economy. Experience and education, ‘gher’ area, share of family labour and tenancy significantly improved TFP growth and technical change. The policy interventions include additional funds in education for ‘gher’ farmers, land and tenurial reforms to consolidate operation size and training for female labourers to improve long-term growth of the ‘prawn-carp-rice’ joint farming.

Nitrate contamination of water in dug wells and associated health risks of rural communities in southwest Bangladesh.

Consumption of drinking water with high nitrate may pose a serious health hazard. This study examined nitrate concentration in the water of dug wells at the Jashore district of Bangladesh. A total of 58 water samples were collected from dug wells which are currently in use for drinking water. Concentrations of nitrate in the water range from 0.05 to 430mg/l and from 0.24 to 206mg/l respectively in the wet and dry seasons. About 17% and 14% of the samples during the wet and dry seasons respectively showed nitrate concentration above the WHO guideline value of 50mg/l. The wells with high nitrate concentration showed health risks for adults and children. About 17% of the samples showed a health hazard index (HQnitrate) values above the acceptable limit (HQnitrate values > 1) for adults, in both the wet and dry seasons, whereas 26% and 33% of the water samples in the wet and dry seasons respectively showed HQnitrate values > 1 for children. Therefore, children are more likely to be affected by intaking nitrate-contaminated dug well water. Health risks of elevated nitrate concentration in the dug wells require proper attention to ensure reliable water supply.

Differential climate change vulnerability among different poverty groups in southwestern Bangladesh: lessons for adaptation planning

This article draws on research findings from fieldwork undertaken in Mongla Upazila of Southwest Bangladesh from 2018 to 2019 to analyse how climate-related vulnerability and adaptation is differentiated among different poverty groups. The principal aim of this research is to investigate complex relationship between vulnerability, poverty, and adaptation in a case study carried out in two rural cyclone-prone areas of southwest Bangladesh, focusing on household level vulnerability and adaptive responses to climate change. The quantitative research strategy was adopted in this research. Specific methods utilized for the data collection process included in-depth questionnaire survey of 98 households. The significance of the results was in the differences of poverty and adaptation choices of the households with differential climate change vulnerability which revealed a complex relationship within vulnerability, poverty and adaptation. This research also highlighted that the poor households with high vulnerability could highly be adaptive through adopting a significant number of adaptations to deal with sudden and gradual changes in climate, but the results also suggest that households who are not poor who have usually low vulnerability, likely to have less adaptive responses than households who have high vulnerability. Moreover, this research is an attempt to reveal the complex relationship among vulnerability, poverty and adaptation that may help to develop more effective adaptation framework than before to deal with climate variability and change.

‘Picking up the neighbours’ waste’: migration of Bangladeshi villagers to India metropolises

ABSTRACTFrom a small area of the South West of Bangladesh, thousands of landless farmers cross the border with their family in order to work in the informal sector, mostly in Delhi and Bangalore: as waster pickers for the men, as maids for the women. Based on two ethnographic fieldworks in the villages of origin, this article intends to highlight the reasons leading to this migratory movement, the way this migration is organized and its consequences for the families. In a context where, in India, Bangladeshi migration is mostly felt as a threat, it also analyses the process of hypervisibility/invisibility to which these migrants are subjected to and the effects that deportability – or actual deportation – have on their life. At last, it examines how migrants experience the discrepancy between the way they see themselves and the way they are largely considered by the Indian authorities and broaden society.

USE OF MOSQUITO REPELLENT: A COMPARATIVE ANALYSIS BETWEEN SLUM AND PLANNED RESIDENTIAL AREAS OF KHULNA CITY CORPORATION IN THE SOUTH-WEST BANGLADESH

People in developing countries like Bangladesh often ignore the harmful effect of using mosquito repellents on health as well as environment. This is a cross-sectional study among adult individuals selected from planned residential (60) and slum (60) areas of Khulna City Corporation in the south-west Bangladesh considering the user (64) and non-user (56) of repellents chosen through applying a stratified systematic random sampling method. Most of the surveyed people use mosquito repellents at evening and at night while sleeping. Poor slum people mainly use local brand coil, while a comparatively high income earner planned residential people use variety of repellents. This study finds that the planned residential people spend more on repellent purchase per month than slum people. The smoke congestion of living room due to use of repellent is more evident in slum areas compared to planned residential areas. Feeling sick due to this smoke is also more evident in the slum areas compared to planned residential areas. Similarly, the severity of disease due to use of mosquito repellent is higher in the slum areas compared to planned residential areas. The planned residential area people are more aware about the negative health effect of using mosquito repellents. The ordered logit estimation result shows that disease awareness of using repellent is higher among educated and planned residential people in comparison with less educated and slum people. Hence, activities under different public health program might be develop to enhance awareness, especially among poor, less educated slum people toward the negativity of using repellents and encourage them towards using alternative means for preventing mosquito.

Community water management to intensify agricultural productivity in the polders of the coastal zone of Bangladesh

Most of the lands of the southern coastal zone of Bangladesh are protected from tidal flooding and storm surges by embankments constructed during the 1960s and 1970s, creating polders. Sluice gates in the embankments connect the canals (former river distributaries) inside the polders to the surrounding rivers, providing the opportunity for water intake from, or drainage to the rivers by judicious management of the gates. Yet, unlike northern and central Bangladesh, the polders have not benefited from the genetic breakthroughs which underpinned the Green Revolution during the 1960s. Flooding during the wet season followed by severe drought and high levels of salinity during the dry season plague the coastal zone, limiting the application of improved technologies that increase agricultural productivity (amount of harvestable produce per unit of land). While the potential of these technologies has been clearly demonstrated, the lack of an integrated landscape approach to water and crop management precludes agricultural intensification in the polders. Therefore, the ability of community-led water management and land-use planning at the watershed level was tested to improve agricultural productivity in a polder in southwest Bangladesh during 2015–2017. Engaging with communities to employ more pragmatic land-use planning (based on topography/hydrology) and scheduling of sluice gate operations has shown the potential to intensify and diversify cropping systems in the polders, and increasing production by twofold to threefold. This was achieved using improved rice varieties and non-rice crops in wet and dry seasons, respectively, enabled by strategic management of the sluice gates to drain the lands as needed during the wet season and to facilitate timely establishment of non-rice crops after rice harvest. The community-based water management approach has been the key entry point for making inroads toward transforming the agricultural production systems in the polders.

Genomic and evolutionary features of two AHPND positive Vibrio parahaemolyticus strains isolated from shrimp (Penaeus monodon) of south-west Bangladesh

BackgroundDue to its rapid lethal effect in the early development stage of shrimp, acute hepatopancreatic necrosis disease (AHPND) has been causing great economic losses, since its first outbreak in southeast China in 2009. Vibrio parahaemolyticus, carrying the pirA and pirB toxin genes is known to cause AHPND in shrimp. The overall objective of this study was to sequence the whole genome of AHPND positive V. parahaemolyticus strains isolated from shrimp (Peneaus monodon) of the south-west region of Bangladesh in 2016 and 2017 and characterize the genomic features and emergence pattern of this marine pathogen.ResultsTwo targeted AHPND positive V. parahaemolyticus strains were confirmed using PCR with 16S rRNA, ldh, AP3 and AP4 primers. The assembled genomes of strain MSR16 and MSR17 were comprised of a total of 5,393,740 bp and 5,241,592 bp, respectively. From annotation, several virulence genes involved in chemotaxis and motility, EPS type II secretion system, Type III secretion system-1 (T3SS-1) and its secreted effectors, thermolabile hemolysin were found in both strains. Importantly, the ~ 69 kb plasmid was identified in both MSR16 and MSR17 strains containing the two toxin genes pirA and pirB. Antibiotic resistance genes were predicted against β-lactam, fluoroquinolone, tetracycline and macrolide groups in both MSR16 and MSR17 strains.ConclusionsThe findings of this research may facilitate the tracking of pathogenic and/or antibiotic-resistant V. parahaemolyticus isolates between production sites, and the identification of candidate strains for the production of vaccines as an aid to control of this devastating disease. Also, the emergence pattern of this pathogen can be highlighted to determine the characteristic differences of other strains found all over the world.

Agronomic Performance of Modern Rice Varieties in South-west Bangladesh

An experiment was carried out in Boro season during November 2018 to April 2019 at two farmer’s fields of Batiaghata and Dumuria sub-district under Khulna district of Bangladesh with the objective of testing agronomic status and adaptability of four modern rice varieties in comparison with the popular mega variety BRRI dhan28. The varieties were BRRI dhan67, BRRI dhan81, BRRI dhan84 and BRRI dhan86. BRRI dhan28 was chosen as a control due to its wide acceptability among the farmers. The soil of the studied area was moderately alkaline and medium to moderately saline. In Batiaghata and Dumuria field, initial soil EC was 3.19 and 3.29 dS/m, respectively and it was 4.7 and 4.8 dS/m, accordingly at maturity stage. It was observed that germination rate, plant height, effective tiller number were significantly higher in BRRI dhan67 than the other varieties but insignificant with BRRI dhan28 (p?0.05) for both fields. All the yield components spikelets per panicle, filled grain and 1000-grain weight were also significantly higher in BRRI dhan67 in compared to the other varieties but insignificant with BRRI dhan28 (p?0.05) for both fields as well. The highest grain yield was observed in BRRI dhan67 in both plots (7.89 and 7.29 t/ha) and showed significant differences among all other varieties (p?0.05). Harvest Index of BRRI dhan67 (51.02±4.2, 57.84±8.6)% indicated that this variety is the best yielder among the varieties. Considering overall performances and facts, BRRI dhan67 showed better agronomic performance and adaptation than the other modern varieties in compare with popular mega BRRI dhan28.

An Integrated Approach for Constraining Depositional Zones in a Tide-Influenced River: Insights from the Gorai River, Southwest Bangladesh

The tidal to fluvial transition (TFT) of estuaries and coastal rivers is one of the most complex environments on Earth with respect to the transportation and deposition of sediment, owing in large part to competing fluvial and marine processes. While there have been recent advances in the stratigraphic understanding of the TFT, it is still unclear whether these findings are site-specific or representative of mixed tidal-fluvial systems worldwide. Yet, research from this depositional domain holds profound societal and economic importance. For instance, understanding the underlying stratigraphic architecture of channel margins is critical for assessing geomorphic change for fluvio-deltaic settings, which are generally vulnerable to lateral channel migration and resultant erosion. Findings would also benefit paleo-geographic reconstructions of ancient tide-influenced successions and provide an analog for hydrocarbon reservoir models. In the Ganges-Brahmaputra Delta of Bangladesh, the Gorai River is one of two Ganges distributaries actively connected to the Bay of Bengal. With fluvial input from the Ganges and meso-scale (2–4 m range) tides at the coast, the Gorai exhibits a variety of hydrodynamic regimes across its 350-km reach, providing a unique opportunity to investigate along-channel depositional patterns across the TFT. This study integrates multiple datasets—core sedimentology, river channel bathymetry, and remote sensing—to provide a process-based framework for determining the relative position of sedimentary deposits within the tidal-fluvial continuum of the Gorai River. The results of this investigation reveal coincident, abrupt shifts in river channel morphology and sediment character, suggesting the occurrence of backwater-induced mass extraction of relatively coarse sediments (i.e., fine sand). Despite being situated in an energetic tidal environment, evidence of tidal cyclicity in cored sediments is relatively rare, and the bulk stratigraphy appears strongly overprinted by irregularly spaced cm- to dm-scale sediment packages, likely derived from monsoonal flood pulses. Such findings differ from previously-studied mixed tidal-fluvial systems and underscore the site-specific complexities associated with this depositional domain.

A conceptual model-based approach to explore community livelihood adaptation under uncertainty for adaptive delta management

ABSTRACT Delta communities worldwide are facing a multitude of challenges in their life and livelihood. In many developing countries, improving the quality of life and livelihood is a key challenge. While development is a central goal of delta planning in such countries, the effectiveness of planning is challenged by uncertain changes in climate and socio-economy. Bangladesh (one of the countries) is moving towards the adaptive delta management approach to deal with such uncertainties. Historical examples illustrate that Community Livelihood Adaptation (CLA) can critically influence the effectiveness of a policy strategy. Therefore, there is a clear need to explore CLA under uncertainty. For that purpose, this paper develops and applies a conceptual model-based approach combining the mental model and scenarios techniques. Our approach starts by using a participatory process to elicit mental models a farmers’ community uses when considering adaptation decisions; we capture these in the form of a cognitive map, and this map can serve as a conceptual model for analyzing livelihood adaptation decision-making in a future-oriented scenario analysis. To illustrate the approach, a case study of cropping decision-making of farmers community at a polder location under the saline condition in the southwest of Bangladesh has been elaborated. Results show that the approach is useful in structuring the cognitive and qualitative nature of complex decision-making process, and helps in understanding the dynamic interactions of farmers’ adaptation decisions with other actors, their environmental attributes, and market traits. It can help policymakers anticipate the adaptation direction of policy strategies.

Seasonal Variability of Forces Controlling Sedimentation in the Sundarbans National Forest, Bangladesh

Southwest Bangladesh, located on the Ganges-Brahmaputra-Meghna delta, is experiencing the impacts of sea level rise (SLR) due to processes at both the local and global scale. In particular, regional alterations of the hydrodynamic network due to embankment construction has drastically altered effective SLR, placing millions of inhabitants at risk of prolonged inundation, and threatening the world’s largest continuous mangrove stand, the Sundarbans National Forest (SNF). In order to effectively employ landscape recovery solutions, an understanding of local sediment transport and deposition is critical. This field-based study investigates the sediment dynamics between the mangrove platform and tidal channels of the SNF using data from a variety of instruments and sediment samples collected within a forested sub-basin (~20 km2) fed by a major tidal channel. We observe profound seasonal variability within the sub-basin, with the wet season exhibiting deeper and longer inundation of the mangrove platform and greater suspended sediment concentrations (SSC). Further, there exists a trend of decreasing SSC and median grain size from the perimeter of the SNF to the interior, and decreasing SSC from the tidal channel to the platform at both locations. We project seasonal platform sedimentation rates ranging from 0.17 ±0.16 cm in the dry season to 1.8 ± 0.35 cm in the wet season. Importantly, the annual deposition rate measured at either location is sufficiently rapid to keep pace with observed rates of effective SLR published in other studies (~1.0-1.7 cm/yr). Based on our results, it appears that many controls on sedimentation are both covariant and of similar importance to land aggradation in the SNF. While inundation depth and frequency will likely increase under future SLR scenarios, sediment supply is threatened by India’s proposed River Linking Project, which could decrease the sediment loads of the Ganges and Brahmaputra Rivers by as much as 75% and 25%, respectively. These rivers provide the sediment for the entire delta, and we predict that with decreasing SSC, some regions—particularly interior sediment depleted regions—may begin to deteriorate and become submerged, including within the SNF.