Remote sensing Riverbank erosion Anthropogenic factors Meandering GISIn Bangladesh, riverbank erosion has turned into one of the most frequently occurring natural disasters, and it affects the socio-economic and livelihood status as well as the environment of the adjoining areas. Kirtankhola River in Barishal, is this kind of river. This study assesses the amount of erosion-accretion, examines river profile, detecting key anthropogenic factors behind it, and signifying channel shifting of the river within 10 years (from 2009 to 2019). The study used Landsat Satellite imageries, geospatial techniques, and a semi-structured questionnaire survey throughout the study area. The study showed that erosion dominants at the left bank of river (17.1 ha/year), whereas the accretion rate is higher at the right (19.72 ha/year). Besides, cross-section at selected points of the river providing an evident indication of the river widening thus river course shifting. According to 61% of the participants in the questionnaire, high waves generated through water vehicles are the main culprit for this extensive erosion. The number of launches has increased significantly within the studied timeperiod, and most of the launches run over 30 km/h velocity, where it should be less than 20km/h. The study explored a mechanism of how centrifugal force produced by water vehicles increases the intensity of riverbank erosion in the meandering area.

Barishal has recently gone through intense land use and land cover changes (LULC). This study aims to assess the changes of land use of Barishal, which were surveyed from 2000 to 2020 by utilizing Landsat TM, ETM + & OLI-TIRS imageries. The ArcGIS-10.4 & the ERDAS-14 Imagine software were used to deal with satellite images and surveyed measurable data for land cover change evaluation of the study area. Both pre- and post-classification change detection scenarios and NDVI analysis were observed to assess the change result from 2000 to 2020. Maximum likelihood classification was utilized to create unsupervised land cover category (water body, urban, fallow, agriculture, vegetation and lowland). After ensuring acceptable value for each classified image (82.16% for 2020, 76.15% for 2010 & 70.96% for 2000 with Kappa values of 0.64, 0.62 & 0.62 for 2020, 2010 and 2000), a change detection study was performed. This study discovered that the highest growth 69.22% of urban area has been improved within 20 years followed by 49.75% and 21.74% of water bodies, fallow lands; whereas the annual change rate was 14.95%, 7.91% and 10.31% respectively. In contrast, 16.28%, 10.48% and 37.20% of vegetation, agriculture and lowland had been reduced and an (-) annual change rate of 16.03%, 7.15% and 9.99% respectively. In addition, NDVI analysis was also observed a decreasing trend of the vegetation and agricultural lands. The results of this assessment could be supportive to design and appliance significant managing appraisals to protect the agricultural degradation, fruitless urbanization of Barishal district.

A unique, consistent, and uniform earthquake catalog is crucial for assessing seismic hazards in any locality. This study aims at compiling and processing a better uniform earthquake catalog, using this catalog to identify the probable subduction zone, and assessing seismicity parameters for Bangladesh. The study area is bounded by the geographical limits 16–29°N and 86–96°E. It includes a sum of 48,342 events which are compiled as 1.0 to 8.5 magnitudes (MW) and time period from 1548 to 2020 yrs. Uniformization is made between the body, surface wave, and moment magnitude scales to unify the catalog in terms of MW. For seismic hazard assessment or prediction studies, this catalog comprises earthquake events from Bangladesh and adjoining regions. The assessed MC obtained is around 4.0–5.0, which leads to a, b value varying between 0.71–1.12 and an a value varying between 4.85–7.12. The findings show that the MC is lower at the border of the Chittagong-Sylhet through Hill tracts than the northern part of the area with an MC 4.5–5.0 and a, b value close to 1.00. The results indicate that the study area is a seismically highly active zone in the context of seismicity parameters. Finally, the compiled catalog, seismicity of the area and a probable deformation front are presented and are recommended for use in assessing seismic hazard analysis in Bangladesh.

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