UPDATE: You can do this even easier with the “Stage Storage Basin Tool” available in my free tools package here
https://ceethreedee.com/ceethreedee-tools

It is quite easy to do perform a stage storage analysis of a simple basin or dam water. This is because all the volumes are compared to a flat elevation, one flat surface (water level), one irregular surface(ground surface).

But what if you want to know the stage storage elevation of a dam wall or a stockpile, i.e two irregular surfaces).

Well you can essentially use the same technique as described here, but you will need to compare the two stage storage analysis’s to get the final answer.

Keep reading to find out how or if your feeling lazy watch the video here.

Basin Stage Storage (Flat to Irregular)

Stockpile Stage Storage (Irregular to Irregular)

By turning our two irregular surfaces into two separate stage storage calculations to a common flat surface, we can then subtract one from the other to form a stage storage of the stockpile.

Firstly we need to create the common flat surface, the best technique is to find the Max RL of the design surface, by looking at the Surface Properties.

On this stockpile the max RL is 1560 . So, I’m going to create a flat plane at 1560 m and add it to a new surface called “CALC LEVEL”

Now we need to limit our calculation to the design extent

So you will need to create a surface that clips the existing ground to the design surface boundary.

Now you have all the surfaces you need, you can create the two volume surfaces to do the stage storage,

• one that compares to the design, – The Subtract Surface
• and another that compares to the existing ground – The Addition Surface

Extract the stage storages for both of them using the technique described in my post here

You will now need to do a simple subtraction between the two stage storages to form a combined stage storage like below.

The finished result it is quite clear. Looking at the area it starts narrow at the bottom, increases to full width where the toe meets the ground, then reduces in size as it goes back down to the crest of the stockpile. The change in volume also reflects with the increase in area.

Do a final check with a volume surface at the end to see if your correct.