Thanks for your answer @Lonnie A !
I managed to find a solution to my problem (it was the unit conversion ).
For those who are struggling in this process here’s what I did :
– First create your geometry in HEC geo RAS, so river, bank, flow path and XSCutLines layer etc.
Do like you were meaning do compute 1D analysis in HEC-RAS
– Export your RAS Data,
– Open your HEC RAS document and import the GIS geometry file, be careful of the unit !! (That was my problem…) Otherwise your imported geometry will be in a completely different place in the coordinate system
– On RAS Mapper import your terrain file if it’s not already done
– Turn on the geometries layer and do the process indicated in @Lonnie A’s second link