Flooding is recurrent in the city of Douala where people develop activities on the banks of rivers. The study conducted in the Logmayangui watershed in this city is intended to contribute to the improvement of floodplain management in the city of Douala. To achieve this objective, we analyzed the land use pattern and identified the impacts of flooding on the activities of the population. For this purpose, a survey was conducted on 250 randomly selected households in the watershed. A longitudinal survey of the watershed allowed us to identify and determine the geometric parameters of the sewage works. These and other situational details such as housing, hydrography, agricultural areas, floodplains, and water supply were located using GPS (Global Positioning System). The results of the survey were analyzed using Excel 2007 software.