Sediment basins

Sediment basins

Select from the tabs below

• Overview
• Key considerations
• Planning and design
• Construction and operation
• Links and references

Other name/s

Sedimentation basin, silt traps, sump

Description

Sediment basins work by slowing water velocity, causing sedimentation of coarse and medium-sized sediments (typically 125μm and larger). Sediment accumulates in the bottom of the sediment basin and regular removal (desilting) is required to maintain the capacity of the basin to remove subsequent sediment additions. An advantage of using sediment basins in agriculture, is that sediment from the farm can be trapped and used back on the farm. In some instances sediment basins can also be used for water capture and re-use, providing additional benefits for the land manager, although care must be taken to not impede the natural flow of water and approvals may be required[1].

Sediment basins can be built in-line (i.e. within existing drain infrastructure) or off-line. Off-line sediment basins provide the greatest capacity for water quality improvement due to increased detention time and opportunity to incorporate a high-flow bypass. However, in an agricultural landscape space is often limited and in-line structures are more commonly constructed. They can be used on their own or in combination with other treatment systems, as part of a treatment train.

In a treatment train sediment basins perform two roles for water quality improvement:

1. Remove coarse and medium sized sediments prior to run-off entering downstream treatment system/s, so that these downstream systems can efficiently treat smaller-sized sediments, nutrients and pesticides.
2. Control flows entering downstream treatment systems by diverting high flows, protecting them from scour and resuspension.

Sediment basins can be either permanent systems, or temporary measures to control sediment loss during high risk periods such as during tillage, land preparation, planting or harvesting.

Services provided

• Water treatment (primarily sediment and some particulate nutrients and pesticides and may also facilitate some pesticide degradation)
• Moderates peak flows and slows velocity, reducing risk of flooding and erosion
• Can facilitate water collection and reuse, if configured for that purpose and consistent with water take allowances and requirements.

References

1. ^ Water by Design (2017), Wetland Technical Design Guideline. [online], Water by Design, Brisbane. Available at: http://hlw.org.au/resources/documents/?topic=Water%20By%20Design.

Last updated: 5 October 2018