Assessment of remote sensing-based indices for drought monitoring in the north-western region of Bangladesh

Monitoring the operational changes in surface reflectances after logging, based on popular indices over Sentinel-2, Landsat-8, and ASTER imageries

Revealing the status of forests is important for sustainable forest management. The basis of the concept lies in meeting the needs of future generations and today's generations in the management of forests. The use of remote-sensing (RS) technologies and geographic information systems (GIS) techniques in revealing the current forest structure and in long-term planning of forest areas with multipurpose planning techniques is increasing day by day. Significant technological advances are in allowing programmers to modernize how they manage data. Sentinel-2, which is a relatively new addition to Earth observing satellites, is a new-generation satellite that has enabled classification and monitoring of land cover change with high precision at ease. Visible R, G, B, and near-infrared (NIR) bands have offered exceptional 10-m spatial reasolution, making them suitable for vegetation monitoring along with the additional 20-m bands to spare especially in chlorophyll content analyses. On the contrary, Landsat-8 and ASTER which have been longer lasting in Earth observation were rougher results especially in forestry studies. In this study, Landsat-8 and ASTER satellite images were compared against the Sentinel-2 images as a reference in conjunction with GIS techniques to monitor and assess the impact of various logging procedures, including selective logging and regeneration silviculture. The investigation employed a range of plant vegetation indices, including NDVI, GNDVI, and SAVI, to evaluate the efficacy of image resolution in detecting forest cover changes in the Kastamonu region, where the timber production is the hightest in Turkey. For selective and regeneration activities, satellite images were taken pre-harvesting and immediately post-harvesting, and index maps were produced. NDVI, GNDVI, and SAVI indices were the most accurate indicators of green vegetation change in the Sentinel-2A imagery. Similarly, for the Landsat-8 imagery, the SAVI, NDVI, and GNDVI indices were found to be satisfactory indicators. As for ASTER imagery, the success sequance was like SAVI, GNDVI, and NDVI. Based on the findings of this study, it has been noted that the ASTER imagery closeness to Sentinel-2A was more remarkable in detecting changes in green vegetation in forested areas. The data derived from ASTER imageries demonstrated superior efficacy compared to Landsat-8 in generating forest cover maps, owing to their proximity to those produced by Sentinel-2. The findings also indicated that ASTER imagery, with suitable spatial and spectral resolution, could still be utilized as efficienly as Landsats to generate forest cover density maps and monitor long-term forest conservation practices, particularly in professionally managed forests. Thus, this methodology demonstrated the capacity for efficient worldwide forest management.

Drought vulnerability assessment and its impact on crop production and livelihood of people: An empirical analysis of Barind Tract

North-Western section of Bangladesh is experiencing a protracted decrease in precipitation, irregular rainfall, and the depletion of ground water, which results in water scarcity and extreme dry weather that impedes the production of agricultural commodities and threatens the people's way of life. Analyzing the precipitation deficit and ground water deficit, along with vegetation cover, temperature condition, and the condition of the vegetation is a crucial component of drought vulnerability assessment. Rajshahi Zilla, a region of Bangladesh located in the middle of the Barind tract, is experiencing a severe water shortage. The irregular rainfall, decrease in rainfall, prolonged absence of rainfall and ground water depletion results in drought. This study aims to access the vulnerability of drought by analyzing precipitation rates, ground water depletion levels, temperature condition, vegetation condition and the vegetative droughts to find out the severe condition of droughts and the severe effects of this in the livelihoods of the farmers and their crop production practices. In this case the study focuses on determining NDVI, NDWI, NDMI, VCI, TCI, and VHI. The VHI results show a significant increase in extreme drought conditions from 2013 (4 %) to 2021 (7 %). By conducting a few questionnaire surveys and Focus Group Discussion the present situation of crop production and the livelihoods of people has been analyzed. Almost 18.3 % of farmers have made a permanent move away from agriculture, and 80 % of permanently relocated farmers report an improvement in their quality of life. Nearly 60 % of farmers believe that the construction of deep ditches has enhanced their crop yield. Once again, more than 20 % are in the same predicament as previously, with over 19 % reporting that deep irrigation has lowered agricultural yield. Comprehending the potential consequences of drought will enable planners and decision-makers to implement mitigation measures aimed at improving the communities' ability to manage drought risk. After analyzing data, it has been found that Rajshahi is facing a critical drought problem, which has led to water scarcity, severely affecting agricultural production and livelihoods.

Delineating the drought vulnerability zones in Bangladesh

The research aims to explore the vulnerability of Bangladesh to drought by considering a comprehensive set of twenty-four factors, classified into four major categories: meteorological, hydrological, agricultural, and socioeconomic vulnerability. To achieve this, the study utilized a knowledge-based multi-criteria method known as the Analytic Hierarchy Process (AHP) to delineate drought vulnerability zones across the country. Weight estimation was accomplished by creating pairwise comparison matrices for factors and different types of droughts, drawing on relevant literature, field experience, and expert opinions. Additionally, online-based interviews and group discussions were conducted with 30 national and foreign professionals, researchers, and academics specializing in drought-related issues in Bangladesh. Results from overall drought vulnerability map shows that the eastern hills region displays a notably high vulnerability rate of 56.85% and an extreme low vulnerability rate of 0.03%. The north central region shows substantial vulnerability at high levels (35.85%), while the north east exhibits a significant proportion (41.68%) classified as low vulnerability. The north west region stands out with a vulnerability rate of 40.39%, emphasizing its importance for drought management strategies. The River and Estuary region displays a modest vulnerability percentage (38.44%), suggesting a balanced susceptibility distribution. The south central and south east regions show significant vulnerabilities (18.99% and 39.60%, respectively), while the south west region exhibits notable vulnerability of 41.06%. The resulting model achieved an acceptable level of performance, as indicated by an area under the curve value of 0.819. Policymakers and administrators equipped with a comprehensive vulnerability map can utilize it to develop and implement effective drought mitigation strategies, thereby minimizing the losses associated with drought.

Natural disasters, livelihood, and healthcare challenges of the people of a riverine island in Bangladesh: A mixed-method exploration

BACKGROUND

Bangladesh's islands, because of their geographical location, frequently encounter crises like floods and river erosion, which pose significant threats to the residents' well-being and livelihoods. To delve into the effects of these disasters on livelihood and healthcare challenges, a mixed-method study was undertaken in a riverine-island near a major river of Bangladesh.

METHODOLOGY

Between February 15th and February 28th, 2023, a cross-sectional study was conducted on an island in Bangladesh. The quantitative method involved conducting a survey of 442 households, with a total of 2921 participants. Additionally, 10 in-depth interviews and 10 key-informant interviews were conducted using semi-structured guidelines. Qualitative interviews were audio-recorded, transcribed verbatim, and analyzed using a thematic analysis. Triangulation was employed in this study through the integration of qualitative and quantitative analysis, resulting in the presentation of findings that offer an in-depth comprehension of the phenomenon being investigated.

RESULTS

River erosions and floods are common and recurring natural disasters that significantly impact the lives of the riverine island inhabitants. These disasters often disrupted their livelihoods, forced many residents to endure substandard living conditions or relocated during flood events. The island faced a low diagnostic prevalence of chronic diseases (e.g., 5.1% of adults were hypertension and 2.5% are diabetes) because of the absence of diagnostic facilities and a shortage of certified doctors. A significant number of chronic illness people in the community turned to alternative medicine sources (39.3%) such as homeopathy, Kabiraj, and Ayurvedic medicine, especially it gets increased during periods of natural disasters. Moreover, reproductive aged women revealed that 79.4% of them gave birth at home, with 6.0% of these home deliveries resulting in miscarriage or infant death. The destruction of crops, unstable job opportunities, an inadequate educational system, and a deficient healthcare delivery system exacerbated the hardships faced by the population affected by these disasters.

CONCLUSION

The failure to seek treatment for chronic diseases and undiagnosed diseases is a significant health issue among the aging adults on the island. Island residents face the challenge of establishing effective prevention strategies for the well-being of older adults especially at the period of natural disasters. It is crucial for the government and non-governmental organizations (NGOs) to collaborate to prevent the negative effects of floods and river erosions. This should include efforts to enhance the quality of education, healthcare services, job opportunities, and financial assistance for rebuilding homes.