Last Updated: 23 May 2018          For: OptiSurface Designer V2.7+

Overview: The Drainage Analysis functionality allows you to calculate various useful surface drainage characteristics such as:

• Ponding Depth Map,
• Flow Paths Map
  

This analysis assumes enough rainfall occurs to overflow all depressions in the field. Ponding is the water that cannot drain away by flowing along the ground surface, so it needs to infiltrate or evaporate to be removed.

Menu:  Tools > Drainage Analysis

Appearance:

Topography

Surface:  Select the surface the calculation will be based: Existing Surface or Proposed Surface

Calculation Grid:  The cell spacing of the grid that the drainage analysis is calculated on. 10m or 30ft is a typical useful value. 

Furrows or Beds

Furrow or Beds Restrict Water Flow Direction:  If furrows or beds exist tick this ON.  

Furrow/Beds Height (m):  The height of the intended furrows in the field. The water will build up in any depressions and then spill across the furrow.  The Ponding Map Depth shows water depth in the furrows, not on the beds.

Furrow/Beds Bearing (deg):  The direction of the furrows relative to North. Use the ‘Pick’ button to click two points to define the direction or type a number in.  Currently, only straight furrows/beds are handled.

Furrow/Beds In 'Valley' Subzones:  Tick this ON to simulate beds or furrows are present where the valley subzone valley runs. This is OFF by default as OptiSurface assumes water can drain in the valley subzone without being impeded by beds or furrows.

Cost Analysis

Typical Gross Income ($/ha/yr or $/ac/yr):  Insert the gross income per hectare (or per acre) per year. 

Loss In Ponded Areas (%):  The loss of crop yield in the areas that pond water in an average year from water logging, weeds and disease.

Loss in Non-Ponded Areas (%):  This is to account the losses in timeliness of operations; i.e. planting, spraying and harvesting can be delayed waiting for the ponded areas to dry out.  That waiting reduced the yield for the rest of the field.  This loss in production is often overlooked but it can be quite significant.