Modeling inlet hydraulic performance using the storm water management model
da Costa, Larissa R.
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The Texas Department of Transportation (TXDOT) uses Type – H inlets as a median drain for divided highways and as lateral drains on feeder roads. The Federal Highway Administration (FHWA) manual presents the hydraulic aspects of drop – type median inlets. These inlets are usually designed using empirical equations, that are time consuming, propagate rounding errors, and have multiple solutions. One of the solutions for such problems is the use of a modeling program to attempt to simulate drop – type inlets. The modeling was performed using over 250 physical experiments conducted on Type – H inlets at Texas Tech University. The experiments were performed in an 8 ft wide by 48 ft long flume, with tiltable slopes of 0.5%, 1.0%, and 2.0%. The U.S. Environmental Protection Agency (EPA) Storm Water Management Model (SWMM) was used to explore the ability of the program to simulate drop – type inlets. The methodology describes the physical models and how the drop – inlets were conceptualized and then modeled in SWMM. The results of the modeling effort found that the simulated values were within 2.0% of the observed values for the approach flow and outflow of the inlet, but could not predict depths well. SWMM can perform adequately for use in designing Type – H inlets with minimum input information, with the caveat that the depth predictions are poor. Future work should include different types of inlets to test the methodology, and refinement of the modeling technique to more accurately predict flow depths.