Design of Minor Stormwater Drainage Systems

Minor storms are frequent and can cause flooding, water damage, pollution, and reduce the aesthetic value of properties. Today we discuss minor storm drainage systems, disconnected roof drainage systems, use of field inlets and pits, and slot drains.

Minor Storm Drainage Systems

  • Minor storms are frequent storms with over a 10% chance of occurring annually.
  • During minor storms, stormwater runoff is usually conveyed through a residency within a piped drainage system, or as a shallow surface of water.
  • Rainwater runoff from the roof is usually discharged directly into a drainage system.

Disconnected roof drainage systems

  • The design of drainage systems for new building works is usually performed by the designer of the building.
  • Your Stormwater Sydney specialist may also be aware of specific design requirements that your council may require.
  • Standards for design may vary depending on the council, some require the connection of roof water to the public street or to a council drainage system, other councils may allow certain downpipes to release water into garden beds.

Use of field inlets/ Pit insets

  • Many councils allow for the use of grated field inlets and pits within residential property grounds, while other councils either oppose their use or forbid their usage.
  • These types of stormwater inlets are highly susceptible to blockages from debris, particularly when surrounded by loose organic garden material.
  • The need for such stormwater inlets in residential properties has become important due to the increasing use of solid, impermeable fencing.

Use of slot drains

  • Slot drains are usually placed in front of garages to catch and redirect runoff from stormwater.
  • Such slot drains will usually only absorb the runoff from small storms.
  • Stormwater also flows over these drains during major storms.
  • Because of their length, the probability of full debris blockage is lower for these drains- complete debris blockage is unlikely to occur along the entire length of the slot drain.

Stormwater Sydney provides Inspection, Cleaning, Maintenance, Repairs, Construction, and Advisory on stormwater systems across Sydney, ensuring compliance with Sydney standards and Council regulations.