Hi, I’m a new user of HecRAS and HecHMS.
I’m trying to model a specific extreme flood event that occured last year in the basin I’m working on.
The problem is that a few km before the main river delta a diversion is constructed (for flood management) creating thus 2 riverbeds, the natural and the constructed one, resulting in two outlet points and two deltaic parts along the coastline. As I first need to create the input data for RAS I’m working with GeoHMS. I must produce the flow accumulation layer but I don’t know how to do it with two outlet points. I have used “dem reconditioning” tool to modify my dem according to a vector layer, which contains my digitized stream network, but still i cannot create the correct flow accumulation layer. I would like to ask:
a) Should I work in GeoHMS only with the natural riverbed or I should create the flow accumulation layer with two outlets? If the second is correct could you help me how to do it?
b)In GeoRAS how should I approach this matter? Is there some way to define the diversion or should I import it as part of the stream network?
I’ve searched a lot on how to deal with this matter but I could’nt find something helpful. As I understand this is not a very common case and in general I couldn’t find case studies modeling rivers with more than one outlet points.
Any advices and guidelines on how to model this specific case, starting with GeoHMS and GeoRAS, would be a great help for me.
Thank you in advance.
Nick