Loose boundary modeling using SFlood for Sungai Junjung / Mohd Eizam Yusof

The sediment transport capacity of a river determines the scour and deposition processes in a river reach. As such, it is quite important to correctly model the loose boundary channels in response to catchments changes either due to human interferences or natural processes. However, current engineering practice indicates that most modelling activities done by using rigid boundary models. This is due to lack of sediments transport characteristics information such as the sediments rating curve at Sungai Junjung. Site observation for hydraulic and sediments transport data including river cross section, velocity, water level, bed load, suspended load and bed material samples has been collected at downstream stations. A flow rating curve which contain the water level data as a function of water discharge (Q) were then established. Later, sediment rating curve which shows the relationship between sediments total load (Tj) and water discharge (Q) also been derived. By using the derived flow rating curve and sediments rating curve the historical water level and sediment discharge values for the ungauged catchment for Sungai Junjung can be derived at any time period from the historical water level records for the study site. The derived parameter then will be use to predict floods level using SFlood Model incorporating with the sediments transport. The simulation is considered in loose boundary condition and the rigid boundary condition. The simulation result show that loose boundary condition gave higher water level comparing to the rigid boundary condition. It’s clear that loose boundary condition affected the river by erosion and deposition. Deposition of sediment cause the flow resistance is higher, thus the water level also increase.