I am designing Stream crossing where I have 10' wide stream. Because of 100 year flow and flood-way condition I am designing 50' Conspan O series Arch culvert. I am getting different result on design as a bridge and design as a Culvert condition.
I Calculated scour at bride and I am getting 30' and 25' scour at left and right over bank, which does not seems right at all.
1) Which is right method in this situation? Design as bridge or Design as Culvert?
2) If Design as a Culvert( Conspan O series is different then HEC RAS Predefined Conspan Shape) then How do I calc. Scour depth?
3)When Design as a culvert How do I put invert of the Conspan O series Arch Culvert? Because if I buried some depth then it is taking some of Channel Cross section area too.