Understanding river flow's spatial and temporal dynamics during extreme hydrological events is crucial for flood risk assessment and sediment transport modeling. This study employs Large-Scale Particle Image Velocimetry (LSPIV) to analyze surface flow velocities during a significant storm event on July 16, 2024, in the Greater Toronto Area (GTA). The analysis compares non-flooded and flooded conditions to evaluate the hydrodynamic response of Black Creek Basin. Violin plots of velocity distribution reveal a sustained high-energy flow regime, with surface velocities ranging from 1.6 to 2.15 m/s. The persistence of peak velocity regions highlights preferential flow paths shaped by channel confinement and bed topography. The rose diagram of flooded conditions indicates a dominant east-to-south flow direction, deviating from non-flooded patterns. This suggests increased discharge modifies the primary flow trajectory and potentially engages secondary flow pathways. Submerged gravel banks and riparian vegetation influence near-bank velocities, affecting flow convergence and divergence. The application of LSPIV in this study demonstrates its capability in real-time flood event monitoring and hydrodynamic model validation. The results provide insight into the interaction between extreme flow conditions and channel morphology, offering valuable implications for flood mitigation strategies and river management. Future work will incorporate additional video datasets for winter conditions to enhance temporal analysis and improve understanding of seasonal hydrodynamic variations.