[sam1]

yes, thank you for your answer, actually this is what i did. But in the HDF file you have the depth in each cell, so cell is considered dry if depth equal 0 and wet if depth>0. But to calculate the flood area extent, is there any other method than considering wet cells? Because the water may not cover all the cell so to calculate the flow extent not all the cell area should be considerd.

[sam1]

No one said that it matters if there is only data for every hour.
And second, i do understand the role of the boundary condition, but what is the problem of having the upstream BC as flow hydrograph as input to the flow area and the Downstream BC as Flow ( with negative values) as outflow of the flow area.

The HEC-RAS 5.0 Reference Manual explains the possibility to have a flow hydrograph as a Downstream or Upstream BC.

[sam1]

You can add Flow hydrograph as a downstream BC with negative values, this means that the flow is flowing out of the flow area.
I dont think this error is related to the time steps, since it does not appear for a 1 days time step but only for 1h.

[sam1]

Thank you for your reply.

I modified the simulation time, now the flow reaches the downstream boundary condition. On the other hand I don’t understand why when the flow reaches the downstream boundary condition the flow disappears ( or empties as you said).
My objective is to export from hec-rass the simulated discarge near the downstream boundary condition. But at this moment, when I draw a profile at this point to export the calculated flow, there are several periods where the flow is 0 because at these periods there is no flow around the lower limit.

Thank you for your help

[Author]

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