Rapid urban development, particularly in floodplain catchment areas, increases the vulnerability of population and capital and the possibility of flood disasters. The loss of life and property damages experienced at Guneysu River basin in Rize province of Turkey between 1974 and 2015 were evaluated in this study. Considering the magnitude of the losses experienced and the severity of the flood event, it was observed that there was a significant increase in the losses despite a lack of growth in the flow intensity. While there was no loss in the past years with similar or slightly higher flow rates, loss of life or property was observed in the following years. In this regard, this study investigates the role of improper land use in the severity of losses due to floods caused by high flow rates triggered by precipitations. For this purpose, the role/importance of flood vulnerability (land use type) in flood losses was investigated in this river basin. As a result of the study, the change in land use was found to increase the risk of flood more than the rate of discharge flow change. During the 40 years from 1973 to 2015, it was observed that the extent of the inundated areas did not increase, but the number of assets increased considerably in the flood zone. In conclusion, this study showed that the role of wrong land use methods increased flood vulnerability in the floodplain catchment areas, and that the consequences of rapid urban expansion increased the risk of flood.