Last Updated: 28 September 2021          For: OptiSurface Designer V3.5+


Overview:  Calculates a design for a ditch network connecting depressions to drain to the edge of the field.

Displayed by:  Tools > Ditch Network Design

Appearance:

• Boundary - select the boundary where the ditch network design will be calculated within.
  
  
• Topography - select the topography which will be the input to the calculation. 
  
  
• Calculation Grid Spacing (m or ft) - define how far apart the calculation grid points are.
  
  
• Calculation Grid Direction (deg) - defines the direction of the calculation grid.
  
  
• Optimization Method - select how the earthworks will be optimized: 
  - Balanced: uses cut and fill and tries to balance them so the cut volume is equivalent to the fill volume
  - Unbalanced: uses cut and fill but does not care if the cuts and fills balance, however, total earthworks will be lower than the balanced option. You could manually balance by taking or depositing earth from an area outside the drain network.
  - Cut Only: only uses cuts to get the field to drain, i.e. there are no fills calculated. This can be used to clean out drains if required or when you have a rotary ditcher that only cuts rather than a scraper which can cut and fill.
  
  
• Minimum Slope - minimum acceptable slope falling in the direction of the ditch.
  
  
• Proposed Ditch Network - tick this ON to create breaklines as guidance lines for the ditch network design.
  
  
• From Cut/Fill Greater Than (m or ft) - define the cut/fill depth when a ditch network will start. For example, when a depression area needs to be filled by 0.001m to eliminate ponding, then a ditch will start from there.
  
  
• Minimum Drain Length (m or ft) - define the smallest length for a ditch line to be created. For example, if a drain line is calculated at only 5m long (which is less than the 10m input) then no ditch line will be formed.
  
  
• Minimum Area To Drain (ha or ac) - define the size of the smallest catchment area where a ditch network will start from. For example, if the catchment area is only 0.01ha (which is less than the 0.02ha input) then the ditch line will not start until the catchment area increases to 0.02ha.
  
  
• Smoothing - defines how smooth the ditch lines are. Higher number means more smoothing and no smoothing forms sharp turns or corners.
  
  
• Delete Previously Created Breaklines - tick this ON to delete the breaklines created from the previous calculation.
  
  
• Proposed Topography - tick this ON to generate a Proposed Topography if you calculate the ditch network on the Existing Topopgraphy. Note that you can also design a ditch network using the Proposed Topography (calculated using the landform design method) as base for the calculation, hence, the option to tick this OFF so it will not overwrite the Proposed Topography.

Example:

This field have several ponding areas that can be linked together and form a ditch network to drain. Ridge subzone was drawn in the south and west edges so the ditch network can only exit north or east.

Satellite Image

Existing Topography

Existing Drainage Analysis

Ditch Network Design
The ditch design was calculated using the parameters below.

Proposed Topography

Cut/Fill Map
Balanced earthworks only ended up at 17 yd³/ac.

Ditch Profile