Water resources in Indonesia are diverse, but it is not easy to process them due to, for example, flooding and rob problems in Semarang. This research examined the hydraulic effectiveness of water-filled rubber weirs through a stability analysis of numerical models. The aim was to analyze the flow load stability as well as the efficient material characteristics. The research was carried out on weir prototypes in the laboratory with variations in the simulation of elevation models in the upstream water level (10 cm to 40 cm) and the simulation of downstream elevation (5 cm to 10 cm). The variables studied were weir weight, mud pressure, earthquakes, and hydrostatics. The laboratory tests revealed that the weight able to withstand the rolling force from upstream was 0.155 (Ton.Meter), with mud pressure of 0.003 (Ton.Meter), seismic force of 0.025 (Ton.Meter), and hydrostatic force of 0.084 (Ton.Meter). The conclusion was that the weir weight has a stabilizing factor. Hence, it can overcome flood mitigation by using efficient materials.