Cut and Fill Volume Differences

AxelG
AxelG
in Raster Data

Hello Global Mapper Forum,

I am working on a project that analyzes erosion and deposition within a stream network using LiDAR change detection. My goal is to determine the volumes of erosion and deposition within a 10m buffer around each stream segment (5m on each side). Here’s what I’ve done so far:

  1. Used the Combine Compare Tool to calculate elevation differences between my LiDAR grids.
    • Negative values indicate erosion, positive values indicate deposition, and 0 indicates no change.
  2. Selected the relevant stream line segment (watershed).
  3. Navigated to Analysis/Measurement > Volume.
  4. Used the Cut and Fill Volumes tool along the selected line feature, with a 10m corridor around the line.
  5. Set the "Use same base height value for all vertices (0m)" option.

Attached is a screenshot showing the area I’ve analyzed, with erosion shown in blue, deposition in orange, and no change (0m) in grey.

image.png

When I run the analysis, I get the following volumes for cut (deposition) and fill (erosion):

  • Cut (deposition) = 286 cubic meters
  • Fill (erosion) = 184 cubic meters

These values seem inconsistent, as most of the stream segment is in areas with negative elevation. Therefore, I would expect the fill volume to be higher than the cut volume.

I also tried calculating the volume using a buffer polygon of the same size (5m on both sides of the stream). I set the parameters to calculate both cut and fill volumes within the area feature and used the "same base height for all vertices (0m)" setting.

image.png

When I ran the volume calculation for the buffer polygon, I got the following results:

  • Cut (deposition) = 61 cubic meters
  • Fill (erosion) = 289 cubic meters

As we can see, the cut volume is much smaller in this case.

My main questions are:

  1. Why do the volumes differ between these two methods if they are essentially calculating the same thing?
  2. Which method should I use for this specific analysis?


Any help would be appreciated

Thank you

Tagged:

Answers

  • AxelG
    AxelG

    As a follow up for anyone interested:

    When calculating the volume along the corridor diameter of the line, I was setting my base height to 0m above ground. When I redid the volume calculation using 0m above sea level, the cut and fill volumes seemed to have been resolved.


    Does anyone know why there is a difference in volume calculations when I compute 0m above sea level vs 0m above ground? I would expect those values to be the same if my DEM is already set to 0m where no erosion/deposition occurred.

Categories

In this Discussion