When using a curb Inlet in sag with a local depression and a long curb opening length, unexpected depth and spread results occur.
For example, there is a sudden jump in gutter depth and spread when the curb opening length is greater than 12 feet.
This is a known issue that has been resolved. Download and install the latest patch set for SELECTseries 5 (2016-Jan 28 or later), or upgrade to a newer version when available. Check the "See Also" section below for information on upgrading and patches.
Note: This is only relevant to gutters with atypical lengths (>12ft).
With this fix, calculations now properly conform to section 18.104.22.168 of the FHWA HEC-22 Urban Drainage Design Manual (3rd Edition).
Unexpected spread and depth results for a curb inlet in sag with local depression
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