Linking Hydrological modeling with Hydraulic modeling

Question

Hi, I am working through a flood modeling project as part of an academic course and attempting to use both ArcHydro and HEC-GeoRAs. Does the watershed delineation process using ArcHydro produce data that is then a necessary input for hydraulic modeling? Are the two modeling processes ever linked or are they usually used for very separate outcomes? I am also wondering if the river schematic produced from the stream definition tool can be used to guide the digitization of the river centrelines in Arc using HEC-GeoRAS.

Thank you for any insight that can be provided.
Myla-Rae

Myla-RaeBaldwin · Answer

Thank you for pointing me to that link. 
Very helpful. HEC-RAS will be tackled later while I explore this avenue. 
Thanks,
Myla-Rae

MarkBoucher · Answer

You can do some approximation using relative water levels. This thread was posted very recently and addresses that.
http://forums.arcgis.com/threads/79620-Calculate-maximum-flooded-area-based-on-maximum-flood-levels-along-a-stream

Myla-RaeBaldwin · Answer

Thanks very much for your reply Mark. I think my team members and I got ourselves a little over our heads with this project, trying to learn HEC-RAS without any hydrological background. In my research I have discovered that many of the decisions that need to be made using HEC-GeoRAS requires a certain level of hydrological knowledge. If we just want to show three possible flood extents over a terrain based on a high, average and low river flow levels over a ten year period, is it possible to do this using only ArcHydro tools? Or does mapping flood extents without having river geometry at our disposal, (only river gauge readings and a DEM) make it necessary to use another software suite such as HEC-RAS/HEC-HMS?

Again, thanks for your timely reply,
Myla-Rae