Culverts are essential components of surface water drainage systems and are often preferred over bridges due to their lower cost. However, scouring at the upstream and downstream ends can weaken culvert foundations, potentially leading to collapse and significant damage to nearby structures. Additionally, blockages during floods can alter flow patterns, increasing the risk of culvert failure. This study examines scour around culverts and proposes various baffle configurations to mitigate it under different flow and obstruction conditions. Numerical models using Flow-3D were utilized to predict the position and depth of scour downstream of circular culverts under both steady and unsteady flow conditions. For steady flow scenarios, maximum flow rates of 13.8 l/s and 20 l/s were investigated. For unsteady flow, two hydrographs were employed, each containing seven distinct flow discharges. The study tested the use of 10 to 11 baffles, each with dimensions of 50 mm in width and 150 mm in height, placed downstream of the culvert in three different configurations to reduce scour. In the first design, the baffles were arranged as 4-3-2-1; in the second, they were arranged as 2-4-3-2; and in the third, as 4-2-3-2. Numerical simulations were conducted for both steady and unsteady flow scenarios, resulting in a total of 48 runs. The results were validated by comparison with laboratory data. Circular culverts with 0%, 25%, and 50% inlet obstructions were analyzed, and the findings were compared with predictions from the Flow-3D software using the Renormalization Group (RNG) turbulence model. The findings were compared to the base case scenario at the same obstruction level. The results indicate that baffles significantly reduce scour under both steady and unsteady flow conditions. They effectively decrease the maximum scour depth (dsm) and limit the development of scour holes compared to the base case at the same blockage rate. In both steady and unsteady flow conditions, the maximum scour depth location (Xsm) is typically near the culvert outlet when baffles are used. Additionally, the inclusion of an inlet blockage increases the deepest scour depth, particularly when combined with a baffle compared with the 0% blockage. However, in the base case without baffles, the inclusion of a blockage does not lead to an increase in scour depth. This required analyzing the downstream scour profile, identifying its location and maximum depth, and comparing these values with observed data. The results revealed the following: • For steady flow conditions and the first hydrograph, option one was the most effective in reducing scour depth across all three blockage rates, achieving reductions of 18.44%, 16.84%, and 16.48% for 0%, 25%, and 50% blockage rates, respectively. • For steady flow and the second hydrograph, option one performed best for 0% and 50% blockage rates, with reductions of 17.89% and 14.77%. Option three was the most effective at 25% blockage, achieving a reduction of 17.58%. • For unsteady flow conditions and the first hydrograph, option one proved most effective at 25% blockage, with a reduction of 29.87%. Meanwhile, option three performed optimally at 0% and 50% blockage rates, with reductions of 28.37% and 27.25%, respectively. • For unsteady flow and the second hydrograph, option one was most effective at 50% blockage, achieving a reduction of 29.13%. Option three performed best at 0% and 25% blockage rates, with reductions of 51.13% and 36.8%, respectively. Although the calculated scour depths were often greater than the observed values for both steady and unsteady flows, the numerical model predictions closely matched the actual data, demonstrating good agreement.
