Flood is a natural hazard. It happens when the water in a river channel is beyond the capacity of the channel to carry while the overflowing water is called as floodwater. Flood causes damage to life and property when it strikes a vulnerable population in the affected area. There are several townships located along Batang Rejang such as Kapit, Song, Kanowit and Sibu. The main objective of this paper is to develop a river model to map the extreme events for Batang Rejang. The method used in is river modelling by using InfoWorks RS software. This method is simulating the Batang Rejang in order to view the behaviours of the river in response to conditions and effects of extreme events over a given period of time. Flood maps computed from InfoWorks RS are for flood extent analysis as it provides insights to the damage for different locations at different flows. The maps are also useful for related authorities or parties to locate human activities at the catchment area and to carry out emergency flood plans in the future.