Dengue fever is a tropical viral disease mostly spread by the Aedes aegypti mosquito across the globe. Each year, millions of people have dengue fever, and many die as a result. Since 2002, the severity of dengue in Bangladesh has increased, and in 2019, it reached its worst level ever. This research used satellite imagery to determine the spatial relationship between urban environmental components (UEC) and dengue incidence in Dhaka in 2019. Land surface temperature (LST), urban heat-island (UHI), land-use–land-cover (LULC), population census, and dengue patient data were evaluated. On the other hand, the temporal association between dengue and 2019 UEC data for Dhaka city, such as precipitation, relative humidity, and temperature, were explored. The calculation indicates that the LST in the research region varies between 21.59 and 33.33 degrees Celsius. Multiple UHIs are present within the city, with LST values ranging from 27 to 32 degrees Celsius. In 2019, these UHIs had a higher incidence of dengue. NDVI values between 0.18 and 1 indicate the presence of vegetation and plants, and the NDWI identifies waterbodies with values between 0 and 1. About 2.51%, 2.66%, 12.81%, and 82% of the city is comprised of water, bare ground, vegetation, and settlement, respectively. The kernel density estimate of dengue data reveals that the majority of dengue cases were concentrated in the city’s north edge, south, north-west, and center. The dengue risk map was created by combining all of these spatial outputs (LST, UHI, LULC, population density, and dengue data) and revealed that UHIs of Dhaka are places with high ground temperature and lesser vegetation, waterbodies, and dense urban characteristics, with the highest incidence of dengue. The average yearly temperature in 2019 was 25.26 degrees Celsius. May was the warmest month, with an average monthly temperature of 28.83 degrees Celsius. The monsoon and post-monsoon seasons (middle of March to middle of September) of 2019 sustained higher ambient temperatures (>26 °C), greater relative humidity (>80%), and at least 150 mm of precipitation. The study reveals that dengue transmits faster under climatological circumstances characterized by higher temperatures, relative humidity, and precipitation.

The urbanization processes and its keen relationship with the spatio-temporal variability of land use-land cover (LULC), land surface temperature and urban heat island (HI) within the district towns in the Rangpur division of Bangladesh has been assessed using multi-spectral Landsat satellite images from 1991 to 2021.The supervised classification approach was used to retrieve LULC types such as water body, built-up area, bare land, agricultural land and vegetation cover. The results of LULC suggest that agricultural and bare land have decreased during the last 30 years in the study areas. The vegetation cover shows an average increase and built-up area has increased progressively from 1991 to 2021. Conspicuously the water bodies, agricultural and bare lands have reduced due to the expansion and rapid growth of settlement areas or urbanization. The spatio-temporal variability of Land Surface Temperature (LST) over the study area responsible for the development of the urban heat islands (UHIs) is assessed using the mono-window algorithm. The areal extents of the UHIs are spreading out day by day and have become most extensive in 2021. Correlation of LULC types with the HI and LST indicated that lower temperature zones were found in the water bodies, vegetated and agricultural lands whereas higher temperature zones were found in the bare lands or highly built-up areas within the district towns. Ground truth data have been validated well with the image processed results with an overall 86.25% classification accuracy which indicates a good level of accuracy of the detected LULC using satellite images. Thus, the research work will help in understanding the land cover dynamics, increasing LST and heat island growth, which could be further used for mitigating the socio-economic hazards faced by the communities in and around the study areas. The Dhaka University Journal of Earth and Environmental Sciences, Centennial Special Volume June 2022: 17-28

Bhasan Char has undergone noteworthy transformations in its geographical characteristics since its emergence in 2003. Driven by sediment transported by the Ganges-Brahmaputra-Meghna river system, the island has gradually transitioned from a stretched-out configuration to a more rounded shape primarily due to continuous accretion, while erosion has been minimal since 2012. Currently, the island is being prepared to accommodate over 1 million Forcefully Displaced Myanmar Nationals (FDMN) refugees. This investigation, conducted over the time frame spanning from 2003 to 2023, utilizes multi-temporal satellite imagery to scrutinize the altering geography of the island, encompassing the processes of erosion and accretion, modifications in the coastline, and changes in land utilization and coverage influenced by seasonal variations. By employing the Advanced Land Observing Satellite (ALOS)/Phased Array Type L-Band Synthetic Aperture Radar (PALSAR), the study pioneers an evaluation of storm surge risks that are specific to this island. Additionally, the research utilizes water indices to understand the seasonal geomorphic dynamics of the island and performs a supervised classification to assess land utilization and coverage alterations. The inundation map shows accretion in the north and erosion in the south and southeast. Southwest is the most stable area with the majority population. After the 'Ashrayan -3′ project, significant land use and land cover changes occurred, including urbanization, embankment construction, and agricultural modifications. The average elevation of the island is 2.84 m above sea level, with a risk of inundation from storm surges exceeding 3 m. Rehabilitated populations are particularly threatened if the embankment height of 4.8 m is surpassed. The study's outcomes indicate that other projects worldwide might use the island restoration efforts as a model. This emphasizes how crucial it is to keep an eye on changes in land cover and use for upcoming planning and adaptation initiatives. Moreover, it highlights the necessity of proper assessments of storm surge hazards to guarantee the security and longevity of island communities.