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Competency Area 3: Drainage and irrigation AEM

PO 18. Know the advantages and disadvantages of:

  1. Surface Drainage
  2. Subsurface Drainage
  3. Random Layout
  4. Pattern Layout

Random Layout

A random layout refers to the irregular pattern in which surface and subsurface drainage systems are implemented into the landscape. A random layout mimics and takes advantage of natural drainage patterns, and thus surface ditches and/or subsurface drains are randomly arranged in depressional topography to improve the wettest areas of the landscape. Random systems are well suited to undulating landscapes, where the higher areas of the topography are already adequately drained. Random systems are less costly to install per unit land area improved, and generally facilitate more efficient cultural operations by reducing turns (around wet areas), allowing for larger areas to be managed as a single unit. A disadvantage of a random layout is that it may not adequately and uniformly drain the area.

Pattern Layout

A pattern layout is a well organized regular spacing of surface and/or subsurface drains across an area. The pattern can be parallel or herringbone shaped (at angles to a slope, channel, or field boundary). Pattern layouts are well suited to long, uniformly sloping fields where the land slope is generally less than 5 to 8%. In land slopes of 3% or less, the pattern can be oriented in any direction to take advantage of optimal field shapes. A pattern layout provides more uniform drainage improvements, but will be more costly per unit land area improved.


Two types of pattern layout drainage systems: a simple parallel system and a herringbone pattern.