HEC22 wizard

HEC22 wizard

This is a procedure for determining the capacity of on-grade pits from geometric data, using methods  presented in U.S. Federal Highway Administration Hydraulic Engineering Circular 22, Urban Drainage Design Manual, 3rd Edition, 2009 (available from www.fhwa.dot.gov/bridge/hyd.htm).

The procedure is implemented using the dialog box shown below, which can take different forms depending on the choice made in the box headed Inlet Type in the top left corner.


These methods have also been implemented in a Generic spreadsheet available to DRAINS users that can calculate pit inlet capacities for all sizes of rectangular pits.

The factors involved are shown in the following diagrams, for pits in gutters and for pits in swales.


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