Multiple Reaches, but not connected? 1

[mahey07]

Hello everyone,
My Question is: I have multiple reaches, but they are not connected to each other. Can I still model them in One HEC-RAS model, or do I need separate HEC-RAS model for each reach? They are part of one Main River though... and I am doing floodplain analysis!

I am not sure how fast are the replies here. This is my first thread. But I would really appreciate an early reply.
thanks everyone!

 

[SMIAH]

Yes you can.

 

[mahey07]

Thansk SMIAH. Can you be a bit more detailed? like how?

 

[SMIAH]

In Geometric Data / River Reach : draw 2 reaches not connected.

Then when you enter cross sections and flow data, you can select one or the other.

So you can set 1 river with 2 reaches.

 

[mahey07]

SMIAH,
I have geometry imported from GIS. And I have 5 reaches, which are not connected to each other, flowing in different directions actually. I still can't follow the step you mentioned. Sorry, if my question is simple. I am new!!

How dO I set 1 river 5 reaACHES?

 

[SMIAH]

Main Menu / Edit / Steady Flow Data

What's written under "River and Reach" and how many (5?)

 

[mahey07]

Thanks. Yes, I have 5 reaches. I am still confused, but I will try running it soon.

PS: I got here - Main Menu / Edit / Steady Flow Data --> Whats next?

 

[SMIAH]

So everything's ok then.
5 reaches in 1 river.
You have to start to create the model.
User Manual?

 

[mahey07]

SMIAH,
Is it discussed in User Manul or Ref Guide? I still didn't find the multiple reach (non-connected) option in "Main Menu/Edit/Steady Flow Data". BUT, I will post more detailed message soon..

 

[SMIAH]

I don't think that there is anything else special abouit the multiple reach apart from entering specific flow data and boundary conditions for each of them.

 

[Ryb01]

Hi mahey07,

Hopefully I'm understanding your question but here's my thoughts.

The reaches should be connected if they are apart of the same watershed. You can connect the reaches with junctions. These junctions will be useful in establishing reach boundary conditions where there is a confluence in the network. This way you will not have to vary the downstream water conditions as you move from downstream to upstream.

Connecting the reaches is quite simple, yet a bit confusing at the same time. If you want to connect say two reaches for an example go into the Edit/Enter Geometric Data window. From there select the river reach tool button at the upper left corner of the window. Draw a line, by clicking on the end of one reach that you want to connect and double click at the limit of the next reach you want to connect. Once you have done this you have created a new reach. This is a dummy reach for the time being. Next you will be prompted to enter the river and reach ID for this "dummy" reach. ID's are not that relavent, just type in an indentifier to you know it's a dummy reach. Next you will be prompted for two Junction ID's connecting this dummy reach with the two other reaches. Once this is complete you will temporarily have three reaches. You can delete both new junctions (or only 1) to connect the reaches.

 

[gbam]

mahey07;
Can you pdf your geometry plan view and upload it so we can take a look at it. A picture is worth a 1000 words.

I am unclear why you would want to model several reaches that are NOT hydraulicly linked in one HECRAS model.

If there is a chance for lateral weir discharge from one to another then they are linked and SHOULD be modeled in a single HECRAS.

 

[mahey07]

Will do it soon. I am out in the field today. But I believe SMIAH's advice would work.

I don't think connecting with dummy reaches would be needed. Moreover, if you connect it with dummy reaches/river, then XS and boundaries would be needed for the dummies!

anyways, will upload the pdf early next week. Not sure if it would help. thanks everyone!