# 3.4.18.2 Design Breakline (OptiLine)

*Last Updated: 22 May 2018 For: OptiSurface Designer V2.5+*

**Overview:**
'Design Breakline' operation calculates an optimized elevation profile for a breakline. The new breakline profile is called an OptiLine. The calculation aims to minimizes the cut & fill distance from the Target Depth while satisfying constraints like slopes and smoothing. This feature is best used to create surface drains or subsurface pipe (tile) drainage. It can also be used in conjunction with design surfaces to combine the benefits of drains/ditches and optimized surfaces.**Displayed
by:**

Right Click Breakline > Design Breakline

**Appearance:**

**Design Breakline****Calculate Using:**

*Existing Topography :*References the Existing Topography for calculation.*Proposed Topography*: References the Proposed Topography for calculation.

**Line Type:**Select the Line Type required:

*OptiLine 1Way™ :*Optimised line incorporating Infinitely Variable Grades™ (IVG™) which drains in one way (1Way). The downslope falls to the last point of the reference breakline.*The reference breakline is the breakline selected to calculate the OptiLine.**OptiLine 2Way™*: Coming soon.

**Point Spacing:**Defines how far apart the calculation points for the OptiLine are.

**Constraints****Minimum Downslope (%):**Minimum acceptable slope in %. Enter a positive slope for falling in the direction of the last point of the reference breakline. Typically 0.05% for minimum acceptable drainage. Note: You need to tick the tick box ‘ON’ to adjust the value and use this constraint in the calculations.

**Maximum Downslope (%):**Maximum acceptable slope in %. Enter a positive slope for falling in the direction of the last point of the reference breakline. Usually defined by erosion risk. Note: You need to tick the tick box ‘ON’ to adjust the value and use this constraint in the calculations.

**Smoothing Distance (ft/% or m/%):**Defines how rapidly the slopes can change. This effectively smooths the surface so the grade changes do not change too rapidly e.g. from minimum slope to maximum slope in a short distance. A typical value is 100 m/% (300ft/%) but depends on how much soil you want to shift versus how smooth you want the finished design. The grade changes are calculated at every grid point. For example, if the point spacing is set to 10m, and Smoothing Distance is set to 100 m/%, then at each grid point the slope can change a maximum of 0.1% (10/100). Eg from 0.1% to 0.2% at one grid point, then the next grid point it could go from 0.2% to 0.3%, etc Note: You need to tick the tick box ‘ON’ to adjust the value and use this constraint in the calculations.

**Min. Depth (ft or m):**Defines the minimum depth allowable for the OptiLine below the Existing Topography surface.

**Target Depth (ft or m):**Defines the ideal depth of the OptiLine below the Existing Topography surface. Note: This in ON by default and cannot be turned OFF.

**Max. Depth (ft or m):**Defines the maximum depth allowable for the OptiLine below the Existing Topography surface.

**Max. Elevation (ft or m):**Defines the maximum elevation allowable for the OptiLine.

**Min. Elevation (ft or m):**Defines the minimum elevation allowable for the OptiLine.

**Example**:

It was determined that this field will have drain channels allowing water to exit to the east. An OptiSurface 4Way was calculated with an Exclusion subzone marking where the drain channel would be.

1. Draw the breakline. Right click Proposed Topography under Project Explorer > Add Breakline. This will serve as the Reference Breakline for the calculation of the OptiLine.

2. Right click the Reference Breakline > Design Breakline. Insert required parameters or constraints.

3. An OptiLine will be calculated.