Need volume of site detention pond

[patricks]

I have a toposurface shaped with a depression area for storm water dentention. I need to know the volume of water that the depression will hold before the water spills over the edges. Is there any way to calculate this?

[sbrown]

Not automatically, I would just do an average based on the area * the average depth.

[patricks]

Well I tried to do a pad to give me the volume below it, but for some reason my pads are not reporting the correct volume.

To test it, I made a pad 5 feet by 5 feet, and the average depth of the fill below the pad is around 1.5 feet. 1.5x5x5 should be 37.5 cubic feet, but Revit is only reporting around 6.5 cubic feet for that area of fill below the pad. The surface area of the pad top itself is 25 square feet, so why would the volume only show up as 6.5 cu ft.?

[patricks]

Nevermind, I had something set wrong before.

So a pad works for determining the volume of water in a certain area of your topography. I needed to find the volume up to a particular elevation, and my pad is 1 foot thick, so I set the pad elevation as 1 foot higher than the contour line and traced that contour line as my pad outline.

Then I just selected the earth fill below the pad and it reports the volume.

[sbrown]

Wow, I'm surprised that works unless the walls of the pond are vertical.

[patricks]

The bottom of the pad was set to the upper-most contour line around the pond. Any higher and the water will be spilling over the berm. So the filled area of earth below the pad is equal to the volume of water the pond can hold.

[barathd]

I used a mass pyramid - worked for me.

Regards

DB

[Dimitri Harvalias]

What about a graded region for this?
Use the orignal topo as the existing, create your duplicate, delete the points inside the boundary of the pond edge, set points around the perimeter of the pond that are just below the corresponding contour around the pond and finish the sketch. The net fill should be your volume.
If there are only the perimeter points for the pond then the interior of the pond should be level.

[patricks]

What about a graded region for this?
Use the orignal topo as the existing, create your duplicate, delete the points inside the boundary of the pond edge, set points around the perimeter of the pond that are just below the corresponding contour around the pond and finish the sketch. The net fill should be your volume.
If there are only the perimeter points for the pond then the interior of the pond should be level.

I dunno, the topo was already graded from the existing, so it's actually the New topo that has the detention pond.

[Dimitri Harvalias]

You could try copying it out to another project and using the new topo as the existing:screwy:

[patricks]

Checking topo cut/fill didn't really work very well because some of the internal points below what would be the water surface were affecting the shape of the 93' contour line (the maximum water surface elevation).

Looks like a pad is the best way, since it will fill in whatever void is below it. So just sketch the pad around the contour line representing the maximum water surface elevation and that will give the water volume.

[Phil Read]

(Area of Base + Area of Top)/2 x Depth. Presumes fairly regular slopes.

-Phil

[patricks]

(Area of Base + Area of Top)/2 x Depth. Presumes fairly regular slopes.

-Phil

The pond is an extremly irregular shape, with no flat area anywhere except what would be the surface of the water.

[patricks]

Nevermind, I had something set wrong before.

So a pad works for determining the volume of water in a certain area of your topography. I needed to find the volume up to a particular elevation, and my pad is 1 foot thick, so I set the pad elevation as 1 foot higher than the contour line and traced that contour line as my pad outline.

Then I just selected the earth fill below the pad and it reports the volume.

Well now I'm having to do this again, and for some reason I'm having the same problem as before, but I don't remember what was set wrong that I referred to in my previous post. :(

Pad 5' x 5' with a fill of about 1.5' below the pad is reporting less than 5 CF fill. :banghead:

*edit* seems the pad's surface is reporting the fill amount above the existing surface. Not sure how to make it read the amount above the new surface.

[ricky rocket]

Has there been any new developments with this issue? It would be great to be able to calculate volumes of topo accurately.

Im open to any suggestions,

Thanks