For a curb opening this would be the case if the depth of storm water at the opening is less than the height of the opening. The openings for storm water drains can be modeled as a weir if the opening isnвЂ™t completely submerged at the design storm water runoff flow rate. The Weir Model for Sizing Storm Water Drain Inlets A sketch of a depressed gutter inlet is shown at the bottom left.Д¬urb Inlet Image Credit: Lone Star Manhole and StructuresД¬ombination Inlet Image Credit: Robert Lawton вЂ“ Wikimedia CommonsДepressed Gutter Inlet Image Credit: H. Gutter inlets typically have a grate over the opening, while curb inlets are typically open without a grate, as shown in the pictures. A combination inlet has both a curb opening and a grate opening in the bottom of the gutter as shown in the image at the right. A curb inlet is just an opening in the curb as shown in the image at the left. The types of pavement drain inlets in common use include curb inlets, gutter inlets and combination inlets.

The links above also have spreadsheets for calculating the peak storm water runoff rate with the Rational Method equation. Read on for information about storm water inlet design and Excel spreadsheets to do the calculations.Дesign of storm water drain inlets is basically determining the size opening needed to handle the design peak storm water runoff rate, for the particular type of inlet opening.

For a storm water drain inlet calculations spreadsheet, click here to visit our spreadsheet store.

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