Incorporation of seasonal land cover to develop seasonally integrated land cover map for change detection in Dhaka mega City

The seasonal cycle significantly alters the spatial extent of land cover (LC); and restricts capturing LC dynamics using a single-date satellite image. This study proposes a new method for producing a Seasonally Integrated Land Cover (SILC) by combining seasonal LCs to capture these rotational land covers. Additionally, SILC has been used to detect land cover changes in Dhaka City between 2000 and 2022. Results showed that SILC exchange occurred among every SILC over the study period, though some were negligible. The major drivers of SILC change in Dhaka City (2000-2022) were the significant expansion of built-up areas (77.80 to 143.75 sq km) and the significant reduction of seasonal wetland vegetation (91.12 to 6.62 sq km). Unplanned urban expansion in and around the city center increased the spatial extent of permanent built-up areas by converting seasonal built-up (16.33 sq km), dry-land vegetation (12.26 sq km), bare land (8.87 sq km), wetland vegetation (7.72 sq km) and permanent (8.03 sq km) and mixed (5.12 sq km) vegetation. Additionally, large areas of seasonal wetland (28.29 sq km) and dry-land vegetation (16.17 sq km) were converted into permanent vegetation due to anthropogenic activities, basically landfilling, shifting its distribution to the peripheral areas, especially in the east. This change also decreased seasonal variation in LCs over time. The SILC maps provide critical insights for Dhaka's urban planning, supporting flood mitigation, green space conservation, wetland restoration, and infrastructure planning. Also helps in regulating urban growth, flood mitigation, and enhance climate resilience through targeted land-use policies.