Figure 1. Satellite image of Dillard field.

Growers in North Carolina and Quebec farm have a unique way of farming their fields. They like farming with long narrow strips about 300ft or 100m wide with a crest in the middle promoting cross drainage. These "sub-fields" are grouped together, with ditches in between each subfield.

As the planting direction follows the length of the field, even though there's a ridge along the middle of the field, reverse grades can be an issue along the farming direction which results to ponding areas as shown below.

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

An OptiSurface 2Way was used to design each subfield independently. Ridge and valleys are used to define the high areas and cross drain. Subzones with defined cross slope parameters split the field to create a ridge line along the middle of field. Minimum main slope is set to 0.05% while minimum cross slope is set to 0.15%.

Figure 3. Proposed Topography.

Figure 4. Proposed Cut/Fill Map.

Figure 5. Field cross section

Total earthworks ended up at 60 yd³/ac (113 m³/ha) which is very low compared to traditional methods. Creating a ridge line along the length of the field can promote cross drainage, but main slope drainage is just as important if not more.