Sunday, August 13, 2000
Dear Ken Potter
Note that the new RCAD 2000 User Manual has been completed, and will be posted on our web site in the next couple of days. I have responded to your questions below.
Sincerely,
Chris E. Maeder, M.S.
Senior Technical Engineer
chris.maeder@bossintl.com
> 1 METAJOBS / REACHES and RCAD MODELS with TRIBUTARIES
>
> Questions
>
> (a) Can you confirm that Metajob in the V 3.0 Manual does mean "model of a Reach"?
This is explained more clearly in the RCAD 2000 User Manual, but a Metajob (which is now called a River Reach) is a single reach of river. Currently, you can have 100 independent river reaches in an RCAD drawing file. There are plans on linking the reaches together to create a dendritic network model.
> (b) If one is using HEC-RAS in RCAD and wishes to develop a model which incorporates one or more tributaries:
> Does one need to have a cross section across a junction (as against a cross section upstream and a cross section downstream of the junction as in HEC's HEC-RAS)?;
> Can one incorporate all the tributaries in a single model (as one can do in HEC.s HEC-RAS) and run the entire model at one time?
With RCAD 2000, you can model an entire reach of river as a single "reach", and then model the tributaries as separate models. You can have either 1 or 2 cross-sections at the tributary junction, it does not really matter to the software.
Currently you cannot run individual reaches as part of one model. As before, we plan to add this capability in a later release.
> (c) If the answer to the 2nd bullet point question in (b) above is Yes, then:
> how does one do it using the cutting cross section method?
> how does one do it (eg say by coding linkages) if entering cross sections manually?
> Note: The V 3.0 Manual is silent on the subject of incorporating tributaries, although it does talk about changing flows to allow for tributary inflow.
See the new RCAD 2000 User Manual. It explains this in detail. However, suffice to state, we model river reaches as separate models.
> (d) Does the RCAD 2000 HEC-RAS Module allow for Split Flows to be analysed, or is this facility still only in HEC-2?
The HEC-RAS analysis engine does not support split flow modeling at this time. Therefore, you need to model the split flow portion of a model using HEC-2.
>
> 2 PROBLEMS WITH IMPORTING and ANALYSING HEC-RAS FILES
>
> 2.1 The HEC-RAS Model and Files
>
> 2.1.1 Description
>
> I have been trying to import HEC-RAS files into RCAD 2000 so that I could generate a longitudinal profile (1:500 "X" axis and 1:50 "Y" axis scales) which I would then export to Autocad to finish the drawing. I have however encountered problems (see 2.2 below).
>
> The HEC-RAS model is of an open drain in an urban industrial / commercial area which discharges to a larger open drain. Flow is sub- critical in the drain being modelled and starting water levels at the downstream end (junction with the main drain) have been separately calculated and entered in the model.
>
> The HEC-RAS Project has 2 Geometric files, 4 Steady Flow files and many Plan files. The Plan and its associated Geometric and Steady Flow files are current at the time of trying to import them.
>
> The Geometric file has 8 box culverts. It also has a Split Flow junction (I fixed the flows manually, ie by iteration in HEC-RAS to obtain an energy balance at the junction). Distances between the sections upstream and downstream of the junction are entered in the Junctions dialog box). The 3rd and 4th culverts (proceeding in an upstream direction) are represented by Sections 22 and 25; Section 23 is the section immediately upstream of 3rd culvert and Section 24 is the section immediately downstream of the 4th culvert.
> Note: The 3rd and 4th culverts are really 1 culvert, but a pipe enters the culvert at about midway along the culvert. To deal with this, I split the culvert into 2 culverts and set up the sections between them, ie 23 and 24 as described above.
>
> The Steady Flow file has 5 profiles.
>
> 2.2 The Problems
>
> 2.2.1 Discussion
>
> Importing: The HEC-RAS files were imported, but:
> · there were 3 warnings. Two (2 ) of the warnings were to do with lack of reach length between Sections 46 and 48 (ie across the junction); the 3rd was a warning associated with Sections 23 and 24, ie the sections between the 3rd and 4th culverts mentioned above.
> · the ID numbers assigned to the cross sections by RCAD were different to those of the HEC-RAS sections
> Note : My general interpretation of the above is that:
> RCAD is not recognising the junction;
> RCAD has a problem with the way Sections 23 and 24 function in HEC-RAS.
To allow people to get all of the cross-sections into BOSS RCAD from a network HEC-RAS model, we import all of the cross-sectional data and related information. However, since the software does not yet place these cross-sections from different network tributaries into separate river reaches within RCAD, and require that all cross-sections within a reach be uniquely numbered, RCAD will renumber cross-sections that "collide" with existing cross-sections. However, it is relatively simple to construct the additional reaches that are necessary, and the transfer the other tributary cross-sections to the appropriate river reaches.
> The Analysis started, but stopped with a message saying that "An error occurred while reading the ineffective flow information at River Station 25 in Reach Job 1"
> Note: River Station 25 is the 4th culvert mentioned above; there is no ineffective flow information in HEC-RAS for Section 25.
This is probably related due to the fact that we only partially support importing of tributary models, as I described above.
> 2.2.2 Questions
>
> (a) Can you explain why the problems encountered with importing and analysis occurred?
>
> (b) Can you advise on what I need to do in RCAD to fix the problem?
> Note: My guess would be that.
> I would need to add at least a 3rd section between the 3rd and 4th culverts;
> I would need to create a cross section across the junction (ie at cross section 47), as well as create 3 Reaches (ie 2 along the drain and 1 for the outflow reach from the junction) using the procedure to be advised by you under Section 1 above
>
> I would prefer not to have to link the cross sections to the Topo Map unless I had to (in particular there could be a problem with sections between the 3rd and 4th culverts - I am not familiar enough with RCAD and culverts to make any sensible guess on this at the moment).
You do not need to link cross-sections back to the topo map, unless you want to. There has been many improvements, however, in providing tools for linking cross-sections back to the topo map. Please refer to the new User Manual for a discussion of these tools.
The easiest way to import your model with a minimum amount of fuss and work, is to break the original HEC-RAS model into separate models. You would delete all the tributaries except for one in each model so that each model contained a unique tributary. Then import all of these HEC- RAS models into a single RCAD drawing file, creating a separate river reach for each model.
> 3 PROBLEMS WITH PLOTTING
>
> What I did in the Cross Section Grid dialog box
>
> The "X" and "Y" axis scales set as 500 and 50 respectively.
> Grid spacings are supposed to be set in Drawing Units. I wanted a 20 mm spacing between the columns (and between the rows), so re the columns, taking 1mm = 0.5 DU (assuming DUs are in metres and a scale of 1:500) I entered 10 DUs.
>
> Problems
>
> I tried to plot 1 cross section. I was only able to plot it using the "Scale to fit" option. When I tried to scale the plot, nothing was registered; I first tried 1 mm = 1DU and then 1 mm = a range of DUs.
>
> Because I could not plot to scale. I was unable to scale the hard copy re the cross sections themselves or the spacing between the columns (the cross sections seemed about right from the "fit to paper" plot). However, with regard to spacing between the columns, the spacings seemed much greater than anticipated.
>
> (a) Why was a plot produced using the "fit to paper" option, but a "plot to scale" plot could not be produced., and what do I need to do to achieve a plot of say 1:500 Hor and 1:50 Vert?
You need to recognize that the Configure Cross-Section Grid dialog box will generate an "exact" scaled grid to the specifications you give it. Therefore, entering 100 for the Horizontal Scale will 100 meters (or feet) per drawing unit. (Make certain that you have specified the correct unit base in the Configure Units dialog box and the Print dialog box. This could be causing you some problems.)
Then, in the Print dialog box, if you specify 10 mm per drawing unit, then when you output the plot, it will show 10 meters / mm.
Note also that you can do some testing, by drawing some lines that are of different length, and then printing these lines out and measuring them on the printed paper. Note that some printers don't print to scale that well.
> (b) If I want spacings between columns of cross sections to be 20 mm, what is the setting value to be entered and how is it calculated?
The simpliest way is simply to test different values. Again, if your printer is not scaling well, trial and error tends to home you in the fastest.
Linear Mode
