Urban sprawl analysis and shoreline extraction in Douala-Cameroon city using optical and radar sensors

The coastal city of Douala is seriously undergoing unplanned urban sprawl due to industrialisation and urbanisation. At the same time, the seal level is fluctuating, modifying the shoreline. This paper extracts the up-to-date shoreline adjacent to the city boundary, quantifies and maps the dynamics of urban sprawl from 1986 to 2020 using both optical and radar sensors. The patterns and trends of urban sprawl are assessed using the post-classification technique. The main land cover units (built-up area, water body and non-built-up area) are calculated for 1986, 2007, 2015 and 2020. Results show that over the study period (34 years), the built-up areas have been dramatically increased by 140% from 78 to 109 km(2). In additional, the shoreline position has significantly changed during the same period. The current position is detected and mapped as accurate as possible from the Landsat OLI 2022 image using a joint GIS-remote sensing approach. These findings are of paramount importance for the integrated management of such a coastal city.