Combining Landforming and Ditching
Figure 1. Aerial shot of Field Hactor after landforming (left) side by side to another field (right) without landforming.
This field is located in Alberta, Canada with shallow depressions scattered all over the field causing ponding as shown in the drainage analysis below.
Figure 2. Existing Topography (left) and Existing Drainage Analysis (right) of Hactor. Drag the slider left or right to view each.
A combined ditching and landforming was determined to be the best solution to eliminate the ponding areas by connect them using waterways and filling up the low lying areas.
An OptiSurface 4Way surface type was used to design the field along with the Ditch Network Design. Because the field is quite large, it is sectioned into watersheds as shown by the white boundary lines. This allows a more detailed design calculation and allows the export of the machine control file to suit.
Figure 3. Existing Topography (left) and Proposed Topography (right) of Hactor. Drag the slider left or right to view each.
The Cut/Fill Map below shows 95% of the field does not require any cutting or filling and the cut/fills are limited to the flow paths. Also note, the cut and fill volumes balance within each sub catchment which further reduces earthworks and reduces the depths of each drain. This helps with machinery trafficking through these drains and limiting the cut required in the outlet of the field.
Figure 4. Proposed Cut/Fill Map.
Below is the long section along one of the longest flow path from south to north of the field. The deepest cut is only 0.8ft.
Figure 5. Waterway (highlighted in yellow) profile.
Figure 6. Field Hactor during landforming operations.
Figure 7. Field Hactor planted with Timothy Grass after landforming.
This example shows how OptiSurface can be used in applications with shallow depressions which are common in naturally flatter topographies including floodplains.
The design is better than a traditional cut only ditch design because of the balanced nature of the cut and fills which ultimately reduced the volume of earthworks required and also allows the outlet elevations to be higher.