Application of Hybrid Flow Data and Dimensional Analysis to Gated-Culvert Flow Estimation

A calibrated flow rating equation is often used to determine the flow rate through a hydraulic structure as a convenient and relatively inexpensive method to avoid the difficulties of direct discharge measurements in an open channel. In South Florida, there are hundreds of gated culverts, where accurate and quick estimation of discharge in real time is critical for effective water resource management. Flow through culverts under various conditions and geometries has been studied extensively; however, studies of stage-discharge relationships through gate-controlled culverts are rare and, to the authors' knowledge, not discussed in any open-channel hydraulics books, relevant journals, or design manuals. In this paper, two approaches to improve the stage-discharge relationships at gated culverts are presented, and case studies demonstrate their successful and cost-effective use: first, the application of computational fluid dynamics (CFD) for flow data simulation to supplement field measurements to resolve data limitations and, second, the application of dimensional analysis to improve gated-culvert rating equations. The proposed nondimensional flow rating approach is useful for data planning and consistency testing of hybrid data (field flow data and CFD results) and reduces the flow types occurring at a culvert, making the flow classification less complex while maintaining reasonable rating accuracy within 6% of field flow measurements.