New Lessons About the Hydraulic Performance of Highway Storm Sewer Inlets

Laboratory experiments were performed with highway storm water curb inlets to 1) reduce the oblique standing wave that extends into the highway from the downstream side of the inlet and 2) determine the effect of highway resurfacing on inlet efficiency. The work was performed at the University of Nebraska Hydraulic Modeling Basin on a section of full-scale single lane highway with a longitudinal slope of three percent and a transverse slope of two percent. All measured flows were supercritical. Four alternatives to reduce the oblique standing wave were tested but produced only minimally better conditions. Further work continues on this problem. Carless highway resurfacing that covers inlet transitions drastically reduces inlet efficiency. Efficiency for this case can be predicted with previously developed equations and is less than one-half that achieved with standard design transitions.