Queensland Contour Banks

Designing Erosion Control Contour Banks with OptiLine

Farmer: Tristan Nitschke
Location: Queensland, Australia
Field Area: 310 ha or 766 acres
Irrigation Method: none
Crops: Wheat, Chickpeas, Cotton

The design worked perfectly, vastly expediting the the project of draining the contour banks and minimizing necessary earthworks.

Tristan Nitschke
Farmer, Queensland, Australia

Problem

The client was looking for a way to improve the existing contour banks on his field and add more to reduce the risk of erosion.

The Google Earth image below show where the existing contour banks are.

Figure 1. Google Earth Background image showing the contour banks.

They surveyed the field and only covered where the contour banks will be. The locations were predetermined and the banks have approximately 0.16% slope. As the spacing between survey points is sparse, the triangulation length was increased from 100m to 500m to form a surface.

Figure 2. Existing Topography at 100m triangulation (left) and Existing Topography at 500m triangulation (right). Drag the slider left or right to view each.

Solution

The first step was to create a working surface. An OptiSurface 4Way without any parameters was used to do this. This basically recreates the Existing Topography as the Proposed Topography.

Figure 2. Existing Topography (left) and Proposed Topography (right). Drag the slider left or right to view each.

Next was to add the breaklines for the contour banks. Breaklines were added in the Existing Topography following the survey points closely and these breaklines were then moved to the Proposed Topography. The breakline elevations were then optimized using the OptiLine parameters shown.

Then, the breakline was offset to create a wide flat surface so the machine control file will pick up the points. The operator will use the centerline to cut the channel base and then use vertical and horizontal offsets to batter up the side slopes to the required height (E.g. 700mm for banks).

Lastly, the Cut/Fill Map was recalculated to show the estimated earthworks and update the cuts and fills in the map.

Figure 3. The parameters used for the New OptiLine Feature (Design Breakline).

Figure 4. Long section of one of the contour banks.

Conclusion

'Design Breakline' operation can use the OptiLine algorithm to calculate an optimized elevation profile for a breakline.  The calculation aims to minimize the cut & fill distance from the Target Depth while satisfying constraints like slopes and smoothing.

Tristan also said,

The design worked perfectly, vastly expediting the the project of draining the contour banks and minimizing necessary earthworks.

The design will also be very valuable in future bank and drain maintenance.


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