Subject: SWMM 5 Culvert Data from FHWA, HDS No. 5, Hydraulic Design of Highway Culverts, 1985
If you use the culvert option in later versions of SWMM 5 then when the inlet control equation flow is less than the computed St Venant flow then the FHWA equations will be used for the current iteration in the SWMM 5 Dynamic Wave Solution.
via Blogger http://www.swmm5.net/2013/08/swmm-5-culvert-data-from-fhwa-hds-no-5.html