Boundary Conditions

[P Shane]

I am trying to model a river length of approximatley 1 Km which links two lakes. I know what the 50 year and 100 year flood flow volume is at the point just upstream of discharge to the lower downstream lake.
For my HEC-RAS model (assuming subcritical analysis) can anyone suggest what would be the most appropriate boundary conditions to use. I would normally use normal depth but will the water level in the downstream lake have to be considered. I have no idea of what the water level in the downstream lake would be during 50 or 100 year flood conditions.
Thankyou

[RDZ]

Yes the water level of the down stream lake is important. To start your model I would use normal depth but you should at least try to find the pool elevation of the lake. Also you said you have the flow rate down stream near the lower lake. This might be a issue considering HEC-RAS assumes your flows start at the upstream station. It sounds like you have some good information to start your model but more information will be needed.