Environmental monitoring is the most popular application of wireless sensor networks (WSNs). At present, WSNs have been used for a number of applications such as soil moisture monitoring, solar radiation mapping, aquatic monitoring, glacial control and climate change, and forest fire alarm. The ability to place autonomous and low cost nodes in large harsh environments without communication infrastructure enables accurate data collection directly observed from interested areas. In this paper, the use of WSNs for realtime monitoring of the hydrological conditions of rivers for flood forecasting and prompt warnings is investigated. This paper describes the design and deployment of a real-time flood monitoring system (RTFMS). The system performs flood forecasting based on readily available data to provide an indication of likely flood behaviour. RTFMS intends to predict flood in rivers using simple and fast calculations, to provide real-time results and save the lives of people who may be affected by the flood.