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I’ve now extended a few cross sections it occasionally complained about, changed my input Flow Hydrographs to 1-minute intervals (instead of 10-minutes or 1 hour), tweaked the lower end Normal Depth to avoid any slant on the last segment of plots, speeded up my calculation time interval to 1 second and all reporting times to 1 minute – and everything is as spiky as before – but in randomly different places.
I had been setting the input Flow Hydrograph – Critical Boundary Condition – Max Change in Flow value to 1, and it had obviously slowed down calculations in the parts where the flow was changing rapidly. I tried it as low as 0.1, which turned a 1-minute calc into 8 minutes, but didn’t reduce the spikiness.
I still see occasional “EG Max WS” values that are 200000 feet above my real surface – never in the same places twice. The “WS Max WS” values are sometimes a bit odd, but always at least physically possible.
The only explanation Google finds:
“EG Max WS: elevación máxima de la superficie de agua. Crit. Max WS: elevación crítica de superficie de agua. WS Max WS: elevación de la superficie de agua.”I guess that means “EG” is the maximum ever seen in calculations? Do we care, if the average value settles on a more reasonable “WS”?
As for “maximum headwaters and tailwaters in the htba parameters”, I’m completely lost. I can’t find anything like that in any of my Htab Parm or Cross Section dialogs. But I suspect it doesn’t matter – my wild spikes are never at the same cross section twice.
To compare with the earlier Stage and Flow Hydrographs plot, here’s essentially the same thing with all the factors speeded up:
Actually puts less water up on the flat bank areas, as I’d guess from less area under the curve. How can the flow be so wrong at the very first cross section where the hydrograph is dumping it into the system?
Thanks, Luis, for giving me things to try, and someone to try to explain this to…
Thank you Luis for the reply! A lot has happened since I wrote my post… I wanted to check the example projects, and noticed HEC-RAS 5.0.5 was there, so I installed it. Can’t find any examples of junctions.
But I did discover RAS Mapper’s editing functions! The Release Notes document announced them like a finished addition, but I notice the Menu choices all still say “BETA”. And rightly so – I saw at least ten “exceptions” yesterday. They randomly re-order a few Cross Sections, or move a couple of them way out in the mid-Pacific on “River (Missing), Reach (Missing)” – and then redraw all your bank lines zigzagging up and down the reach, or flipping around to the other end of it. If you can get through fixing those without generating any new ones, it will automatically fix all your bank lines… If they ever make editing reliable it will be wonderful!
So I was able to edit those junctions with the Terrain visible under them, and cleaned up several places where my original river lines didn’t match the new 1-meter LIDAR DEM.
There is still a pileup of water ahead of junctions, but it is now ~5 feet instead of ~32 feet. But the “Max WS” levels still wildly overreact to every little bump in the streambed! A 2′ rise to a downstream cross section can make a 100′ spike in the Max WS. I guess that’s what they mean by “unstable”?
All my junctions have less than 2′ drop across the adjacent cross sections, similar to differences between other cross sections. Does that require a “direct drop”?
The cross sections joining the reaches are as close to the junction as they can be without being a star of arrow points. Maybe that’s what I need, a really short perpendicular line with splayed tails barely avoiding each other?
But I’m now seeing worse pile-ups midstream than at the junctions, so I think my scenario is just way too sensitive all over. Maybe little ~1 cfs and ~2 cfs wandering mountain streams are just tricky to model?
Thank you gerar200 for pointing me to the right menu!
I started with this – QGIS on the left, Geometric Data Editor on the right, showing cutline 19380 extending well beyond the bank line to the (screen left) west on the “right” side of my stream looking downstream. HEC-RAS shows all cutlines L-R reversed:
Cross 19380 original QGIS, with HEC xyz plot.JPGI used this on 19380 (in HEC-RAS 5.0.4):
HEC_RAS -> Edit -> Geometric Data Editor -> GIS Tools -> GIS Cut Lines -> Reverse Cut Lines -> (select river and reach – “all” shows no items! But see below…)–> Check the “Node Types …” button before selecting lots of items! Sometimes it has all node types selected, even though you triggered it from a Cross Section specific menu item.
And while it reversed the XS left right arrow as expected, it also reversed the geometry, moving the whole channel westward and reversing the shape of it, leaving the wide bank area on the (screen right) east, “left” side of the stream:
Cross 19380 original QGIS, with Reverse Cut Lines.JPGSo I reversed that back and tried the other option:
HEC_RAS -> Edit -> Geometric Data Editor -> GIS Tools -> GIS Cut Lines -> Reverse XS Stationing and Cut Line Data
(For a single XS line, in Geometric Data Editor, left click the line, select “Reverse XS Stationing and Cut Line”, which does the same thing.)These options reverse the HEC-RAS idea of left and right, _without_ moving the stream channel or spoiling the elevation profile.
Cross 19380 original QGIS, with Reverse XS Stationing and Cut Line Data.JPGIf you’re flipping your entire reach, you can click “All RS” to have the right arrow select all of the stations (you won’t see any action until you click the right arrow…) If you’re flipping your entire project, you can click “All Rivers” when the dialog first opens to have the right arrow select everything.
To see handy XS direction arrows in Geometric Data Editor, View -> View Options … -> Cross Section Properties -> XS Direction Arrows
To see map coordinates in Geometric Data Editor, hold Ctrl key, click a point.
P. 6-187 “Reverse Cut Lines” in the HEC-RAS “User’s Manual” Version 5.0 February 2016 sort-of describes the first function. I guess P. 6-166 “Reverse Stationing Data” must be trying to describe the other option, but it doesn’t match my HEC-RAS 5.0.4 at all, and isn’t very helpful.
Does anyone have a PDF manual that allows copying text? I can hardly believe it, but all the ones I’ve found are “protected”.
So I think my left-right issue is solved! I wonder what I get to learn next…
