Ditch Network With Balanced Cut/Fill
The field is located in Canada with large depressions scattered all over the field as shown in the Ponding Map below.
Figure 1. Existing Topography (left) and Existing Drainage Analysis (right). Drag the slider left or right to view each.
As the Existing Topography is somewhat rolling or undulating, a pure landforming solution is not the best option. On the flip side, a pure ditching solution is not the best option either because ditches are always cutting and end up deeper than they need to be if some filling in depressions can be achieved.
So an OptiSurface 4Way was used to design the field. This surface type lets water meander across the field and exit to the boundaries. In addition, a Ditch Network Design was calculated to create guidance lines for the earth moving operation.
Figure 2 shows the final design.
Figure 2. Existing Topography (left) and Proposed Topography (right). Drag the slider left or right to view each.
Figure 3 shows a typical long section along one of the longer ditches through this field.
Figure 3. An Example Ditch Profile.
Figure 4 shows the Cut/Fill Map. The cuts and fills only occur where earthworks is absolutely required. The cuts and fill also balance which means the lowest possible volume of earthworks is required and the cuts for the ditches are at the lowest possible which makes them easier to farm through and maintain.
Calculated earthworks (cut volume) on average is only 39 yd³/ac, which is an extremely efficient design.
Figure 4. Proposed Cut/Fill Map With Ditch Paths.
This example shows how OptiSurface can be used in applications with rolling topography and deep depressions which common through the pot hole region of northern USA and Canada.
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.