Onsite Detention (OSD) - Overview
Stormwater onsite detention (OSD) refers to the temporary storage of stormwater on a property before it is slowly released into the public stormwater system or natural waterways. This is crucial for mitigating flood risks in urban areas, where impervious surfaces such as roads, rooftops, and driveways increase the volume and speed of runoff during rainfall events. Without OSD, stormwater can overwhelm drainage systems, causing flooding and damage to downstream properties.
Why is On-Site Detention Required?
As urbanization increases, natural landscapes are replaced by hard surfaces that prevent rainwater from infiltrating into the soil. This leads to higher runoff volumes and more frequent flooding in downstream areas. On-site detention systems help reduce this risk by temporarily holding back stormwater on private property and releasing it at a controlled rate. Most councils in Greater Sydney and other regions across Australia mandate OSD systems for new developments to ensure proper stormwater management and flood mitigation.
When is On-Site Detention Required?
On-site detention is typically required for new developments, redevelopments, and subdivisions, particularly where increased impervious areas are created. Councils determine whether OSD is necessary based on factors such as the size of the development, existing drainage systems, and local flood risks. Residential, commercial, and industrial projects may all need to incorporate OSD systems to comply with council regulations and Australian standards.
Types of On-Site Detention Systems
Below-Ground Detention: Below-ground OSD systems are commonly used in urban developments where space is limited. These systems include underground storage tanks or pits that temporarily hold stormwater. Once the storage capacity is reached, the water is slowly released into the stormwater system via an outlet structure.
Below ground rainwater tank and onsite detention (OSD) Above-Ground Detention: Above-ground detention systems involve surface-level storage areas, such as detention basins, swales, or landscaped areas that double as green spaces. These systems provide a natural way to manage stormwater while enhancing the aesthetic appeal of a property. Above-ground detention is often used in larger developments where more land is available.
Above ground OSD Rainwater Tank Combination Systems: In some cases, rainwater tanks can be combined with OSD systems. These tanks capture roof runoff, store water for reuse (such as irrigation or toilet flushing), and also provide temporary detention during heavy rain. Dual-purpose systems maximize the efficiency of rainwater management while reducing demand on mains water supply.
Rainwater tank OSD combination tank
OSD Design and Compliance
The design of OSD systems must comply with local council requirements and Australian standards to ensure they effectively manage stormwater. This includes selecting the appropriate size of the detention system based on factors such as site characteristics, rainfall patterns, and the type of development. At United Hydraulic Consultants, we specialize in designing custom OSD systems that seamlessly integrate with your building design while meeting all regulatory standards.
Our team uses advanced modelling software to calculate the optimal size and configuration of your OSD system. We work closely with developers, architects, and councils to deliver efficient, cost-effective solutions tailored to your project’s unique requirements.
Conclusion
On-site detention is an essential part of managing stormwater in urban developments, helping to prevent flooding and protect downstream properties. Whether your project requires below-ground, above-ground, or rainwater tank OSD systems, United Hydraulic Consultants is here to provide expert guidance and tailored solutions that meet local council regulations. Contact us today to discuss how we can assist with your OSD design and ensure the success of your development.
For expert and tailored assistance with OSD requirements for your development project, contact United Hydraulic Consultants today. Our team provides comprehensive support and guidance throughout the planning and execution process.
Reach out to us at 0432 539 469 or email us at admin@unitedhydraulic.com.au for a consultation or free quote.
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