Sediment basins

Sediment basins

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

Other name/s

Sedimentation basin, settlement pond, settling basin, silt traps, sump

Description

Sediment basins are designed to trap and store sediment and debris. They work by slowing the water velocity, causing sedimentation of coarse and medium-sized sediments and associated nutrients. Sediment accumulates in the sediment basin and periodic removal (desilting) is required. An advantage of using sediment basins in agriculture, is that sediment from the farm can be trapped and reused. 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 either permanent systems, or temporary measures to control sediment loss during high risk periods such as during tillage, land preparation, planting or harvesting.

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 basins 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 downstream systems are not smothered with sediment and 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.

Services and benefits

• Water treatment (primarily sediment and some particulate nutrients and pesticides)
• Moderates peak flows and slows velocity, reducing risk of flooding and erosion
• Soil lost from the farm can be trapped and re-used
• 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: https://waterbydesign.com.au/.

Last updated: 5 November 2022