Rethinking Water Sensitive Design.

The design of a stormwater system is not a simple task, is there another solution?

Site conditions might require one design, yet stakeholder wishes and local body guidelines provide additional, and often conflicting viewpoints. Water sensitive design adds further complexity to the task, especially in increasingly intensifying urban environments, as emphasis is placed on using entirely natural components to achieve an already difficult result.

Whether a new subdivision or redeveloping an existing urban site, water quantity and quality is high on the priority list. Achieving good amenity and biodiversity is also key for human interaction with a project and to complete the requirements for a water sensitive design solution. Mimicking natural hydrology requires managing water flows throughout the system to match pre-development flow rates.

Surface flows can be impossible to achieve on flat sites, or be difficult to control when the gradient is too steep, and overland flows can quickly become a hazard. Even in new developments, devices such as speed tables can quickly disrupt the drainage scheme, creating dams at every pedestrian crossing. Treatment devices such as rain gardens function well in theory, yet ongoing maintenance requirements are often overlooked, resulting in reduced performance.

Using a proprietary drainage device in conjunction with traditional water sensitive design components can achieve a more efficient outcome, often at a reduced cost. Independent comparisons between pit and pipe and grated channel systems showed savings of up to 25%, with significantly improved hydraulic performance. Water is captured from the surface along the length of a channel drain and conveyed off the surface to a treatment or storage device. Products such as Qmax, a slot drain with high capacity channel, can be used for capture and detention within the same device. Exploring these options allows for greater spacing between devices such as manholes or rain gardens, and associated infrastructure. The same Water Sensitive outcome can be achieved with greater flexibility and capacity, all without compromising the overall outcomes.

ACO Limited has unrivalled experience providing technical support throughout all stages of a project. Engagement during concept stage can help inform landscape and civil strategies, and provide initial product recommendations. Aesthetics are important, ACO’s range includes bespoke grate patterns, slot channels and a variety of materials. Ask ACO today to help with your project at info@aconz.co.nz or
0800 448 080.

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