Culverts are vital for channeling water flow beneath roads, railroads, and other structures. Accurate modeling of their hydraulic performance is crucial for effective flood risk management and infrastructure design. This study employed computational fluid dynamics (CFD) modeling to evaluate the hydraulic behavior of culverts beneath the railway crossing at West Main Kanal in Indramayu. Simulations were conducted across a range of discharges, from 25% to 188% of the design flow, analyzing flow patterns, water depth, and velocity distribution. The results showed that the side spillway and culvert effectively reduced excessive discharge to the outlet channel for inflows up to 150% of the design capacity, preventing overflow into the adjacent paddy fields and railway corridor. However, at inflows exceeding 175%, the structure experienced zero or negative freeboard, leading to overtopping and potential inundation. The average velocity within the culvert remained within subcritical flow conditions across all scenarios. The safety performance analysis revealed a clear transition from safe to critical operating conditions beyond 125% inflow. At 175% and 188%, the composite safety score exceeded the high-risk threshold, indicating increased overtopping hazards. These findings confirm that the culvert can safely convey flows up to 150% of the design discharge, but higher flows may require supplementary flood mitigation measures to protect the surrounding infrastructure.