What would be the best way to create a stage storage report with a basin that has mulitple depressions and high points in the bottom of the basin?
The stage storage report seems to calculate these features as an addition when it should be subtracting for high points.
Could I do a bounded volume and set the datum to each increment of storage? How accurate is that? If it's accurate, is there a way do generate multiple at a time instead of typing D then setting the datum, then repeating that process over and over?
The only way that seems the most accurate is to create multiple planes at different increments, add those to seperate surfaces, then a volume surface for each one comparing it to the basin. This method takes up a ton of time, especially when dealing with 50+ increments.
Solved! Go to Solution.
Solved by BrianHailey. Go to Solution.
Create a surface for your high water elevation (WSEL).
Create a volume surface between your WSEL and pond.
Run an Elevation Analysis on the volume surface using the Range Interval with Datum option (set your datum to 0).
Create an elevation table for the volume surface.
Edit the table to show the range volume.
Thanks so much, I'm going to try it out and as soon as I'm able to replicate what you have done, I'll accept it as the solution.
You can also type StageStorage into the command line and automatically create a table for export to text or to create in the current dwg. Tsis command works with surfaces and polyline contours.
John Mayo
The stagestorage command does not accurately calculate basins with depressions and mounds in the bottom. Say if you had a small mound in the bottom of your basin, C3D does not subtract this contour from the report correctly as it should.
I used Brians method and manually checked it and it is accurate. I had to create an excel template to be able to export the result into to generate a report in our format our engineers will accept though. These guys accept less formats than C3D point formats, and you can't train them to learn new ones either...
Depends on you model and data whether it picks up depressions (user contours) but it is after all an avg end area.
John Mayo
Don't use the range volume values from the elevation analysis. They are not the volume of that elevation stage. They represent the volume of all material above that range area.
You can use the Surface Range 2D areas. Incrementally adding them, starting with the lowest, to generate the area of each elevation range.
@david.zavislan wrote:Don't use the range volume values from the elevation analysis. They are not the volume of that elevation stage. They represent the volume of all material above that range area.
You can use the Surface Range 2D areas. Incrementally adding them, starting with the lowest, to generate the area of each elevation range.
I disagree. Go ahead and use them, just understand what they are. They are not a cumulative volue, they are the volume of that specific range. For example, I created a pond with two low points (two pyramids side by side basically), and a water surface elevation surface (the same elevation as the top of the pond), created a volume surface, ran a surface analysis, and then created the table showing the surface range volume.
I then extracted the contours from the surface to check the table (I used the conic approximation equation) and it matched almost exactly.
The range volume is just that, the volume from the top of the range to the bottom of the range. If you want a stage storage, start at the bottom range and that's the volume up to that elevation. Add in the next range at that's your next Stage Storage point. Add in the next range and that's the third Stage Storage point. You just need to keep adding the ranges as it gets deeper.
I'm a little confused. David said "They represent the volume of all material above that range area." But Brian says " they are the volume of that specific range...the volume from the top of the range to the bottom of the range." Which is it? I hope Brian is right; his explanation makes more sense to me.
So then, this does incremental volumes rather than cumulative? That's fine, so long as I can bring the table into a spreadsheet and add a formula in the next column to find the cumulative. The table should also include the surface area at every stage.
Mark Green
Working on Civil 3D in Canada
Thanks Brian. It appears that I was also confused. If I slow down and check the calculations (As we should always do!) I find that the numbers listed in the table are very close to the values calculated using the extracted contour areas and the average end area method. The volumes in the table are no where near the total volume above a region (area x depth) as I had originally believed.
If I would have checked this before my original post on this thread, I could have avoided the embarrassment of claiming to know something that I obviously did not.
That's the beauty of this forum, post something up and if you misunderstood something, someone is bound to pipe up and give an alternate view.
Don't think of it as, "I messed up and gave the wrong answer", think of it more along the lines of, "Now I know something I didn't before." Whatever you do, don't stop answering questions, it's a great way to learn!
As far as the average end area, try the prismoidal method instead, it will give an even closer approximation:
V=(H/3)(b1+b2+sqrt(b1*b2))
HERE is a little write up I did on volume calc methods.
I've been using this method since you responded and it sure saves a ton of time.
Is there a way to get the contour areas for each interval? I know there is a 2D area option in the table style, but this seems to get an odd area.
Basically when I run this, it would be ideal to get as table data headers:
Elevation Interval Range | Contour Area of Min and Max Interval in Range | Interval Volume
Thanks again for all the help in this!
The 2D area is probably giving you the area of the color itself (think of it as a hatch). There's no way that I'm aware of to accomplish this. Sounds like a good item for the wishlist group.
I found that the lowest range seems to give an accurate area. Using that and the volumes in Excel, I was able to get the remaining areas with a bit of backward calculations.
Thanks again!!
Brian,
Who said anything about not posting on the forums? The intent of my "embarrassment" comment was to stress the importance of checking the numbers. Whether it's posting on the forums or a submittal for a client. We should make sure that we understand, and verify, the results generated by any software program that we use.