Enter LiDAR and QGIS Channel Data
Example Data Table
| Station | Spacing | Bed Elevation | Design Elevation | Bottom Width | Side Slopes | Purpose |
|---|---|---|---|---|---|---|
| 0 | 25 | 101.20 | 103.40 | 8.5 | 1.8 : 1.6 | Upstream control section |
| 50 | 25 | 100.60 | 103.10 | 10.1 | 1.6 : 1.4 | Mid channel estimate |
| 100 | 25 | 100.10 | 102.80 | 11.4 | 1.4 : 1.2 | Downstream check section |
Formula Used
Depth: depth = design elevation − bed elevation
Cross section area: area = bottom width × depth + 0.5 × left slope × depth² + 0.5 × right slope × depth²
Section volume: volume = cross section area × section spacing
Total volume: total volume = sum of all section volumes
Adjusted volume: adjusted volume = total volume × (1 + bulking percentage ÷ 100)
Material mass: mass = adjusted volume × dry bulk density
The prismoidal option adds a small smoothing adjustment. The trapezoidal option applies a conservative reduction. These options help compare planning estimates.
How to Use This Calculator
Prepare channel transects in QGIS from a LiDAR DEM or surface model.
Enter each station, section spacing, bed elevation, design elevation, bank elevations, width, and side slopes.
Select the preferred volume method. Add density, bulking, and uncertainty values.
Press the calculate button. The result appears above the form and below the header.
Use the CSV option for spreadsheet work. Use the PDF option for a simple report copy.
LiDAR Channel Volume Planning Guide
Purpose
Channel volume work often starts with a LiDAR surface. The surface is cleaned, clipped, and checked inside QGIS. Then transects are drawn across the channel. Each transect gives a bed elevation, width, bank height, and profile shape. This calculator turns those measured sections into a clear volume estimate.
LiDAR and QGIS Inputs
A good result depends on good input data. Use a corrected DEM when possible. Remove bridges, dense vegetation, and obvious spikes. Check the vertical datum before comparing water levels or design grades. A small datum error can change volume quickly. QGIS profile tools can help sample cross sections. Export station data and enter the key values into the form.
Section Method
The tool estimates each section area from bottom width, depth, and side slopes. It then multiplies that area by spacing. This is close to the average end area approach used in earthwork planning. The prismoidal setting adds a smoothing allowance. The trapezoidal setting gives a slightly conservative comparison. Use close station spacing when the channel changes fast.
Practical Review
Review the maximum depth and average area before using the final volume. These values reveal unusual sections. Compare the output with field notes, survey shots, and recent imagery. LiDAR may miss submerged bed features. It may also include noise from plants or debris. Add uncertainty when the surface is old, rough, or partly obstructed. Use bulk density only when material mass is needed. Keep the original raw volume for audit records.
Reporting
The exported CSV supports checking in spreadsheets. The PDF button prints the visible report area. Keep station spacing, datum details, DEM source, and processing notes with every project file.
FAQs
1. What does this calculator estimate?
It estimates channel volume from LiDAR and QGIS cross section values. It uses spacing, depth, width, side slopes, and adjustment inputs.
2. Can I use QGIS profile data?
Yes. Export or read station, elevation, and width values from QGIS profiles. Then enter those values into the section table.
3. Which method should I choose?
Average end area is a practical default. Prismoidal is useful for smoother terrain. Trapezoidal can support conservative planning checks.
4. What unit should I use?
Use one unit system consistently. If elevations are in meters, spacing and width should also be in meters.
5. Why add uncertainty?
LiDAR may contain vegetation, water, bridge, or datum errors. Uncertainty gives a practical range around the final volume.
6. Does this replace survey work?
No. It supports planning and review. Critical design, payment, or legal work should be checked with reliable survey control.
7. What is bulking or shrinkage?
Bulking increases volume after excavation. Shrinkage lowers placed volume after compaction. Enter negative values for shrinkage.
8. Can I download the results?
Yes. Use the CSV button for spreadsheet data. Use the PDF button to save or print the report view.