Ku-ring-gai Council Stormwater & Drainage Requirements

Building in Ku-ring-gai: Leafy Streets, Strict Controls

Ku-ring-gai is one of Sydney’s most established and most protected residential areas. Knock-down rebuilds and high-end new homes dominate in St Ives, Turramurra, Pymble, Wahroonga and Killara, while apartment and townhouse activity clusters around the rail-based local centres of Gordon and Lindfield. Land values reward ambitious projects, but the LGA’s planning controls – particularly around trees, landscape and water – are among the most demanding in Sydney.

Stormwater is assessed rigorously here, and drainage design that ignores the tree canopy is a common reason for requests for additional information and redesign.

The Planning Framework

Two development control plans operate in the LGA: the principal Ku-ring-gai Development Control Plan, which applies to most residential land, and the Ku-ring-gai Local Centres Development Control Plan, which applies around centres such as Gordon, Turramurra, Pymble and Lindfield. Both contain a dedicated Water Management part (Part 24) setting out controls for on-site stormwater management, stormwater disposal, water quality and riparian protection.

A notable feature of Ku-ring-gai’s approach is that stormwater disposal controls depend on the property’s drainage situation – whether the site can drain by gravity to the street, to a Council drainage system, or only to a downstream property – so two neighbouring blocks can face quite different requirements.

What Builders Are Typically Asked to Provide

• On-site detention: New dwellings, dual occupancies and multi-dwelling projects are generally expected to manage post-development flows through on-site detention or retention so that downstream systems and properties are not burdened with additional runoff.
• Stormwater management plan with the DA: showing collection, the detention system, overflow paths, the discharge point and any treatment measures.
• Water quality and re-use: The DCP addresses stormwater quality and water recycling beyond BASIX commitments, particularly for larger projects; discharges to waterways and riparian land must be treated first.
• Easements for rear-falling blocks: Where gravity discharge to the street is impossible, Council expects an inter-allotment drainage easement – pump-out solutions are accepted only in limited circumstances.

Detention volumes, discharge rates and design storms should always be confirmed against the current DCP and Council’s engineering requirements before design is finalised.

The Local Challenge: Tree-Sensitive Drainage Design

Ku-ring-gai’s identity is its canopy – remnant Blue Gum High Forest and Sydney Turpentine-Ironbark Forest are critically endangered communities, and mature trees are protected across the LGA. For stormwater design this has real consequences:

• Pipe routes and OSD tanks must avoid the tree protection zones of retained trees; trenching through major root zones will not be supported.
• An arborist’s input is often needed alongside the drainage design, and non-destructive excavation or above-ground detention may be required near significant trees.
• Deep, well-drained soils on the ridges contrast with sandstone benches on gully slopes falling toward the Lane Cove River, Cowan Creek and Garigal/Ku-ring-gai Chase bushland – discharge to these bushland edges must be controlled to prevent erosion.

The smart approach is to design the stormwater system and the landscape/tree retention plan together, not sequentially.

How Builders Should Prepare

• Get the site survey to capture all trees (including neighbours’ trees near the boundary) – they constrain tank and pipe locations.
• Determine early whether the block drains to the street or needs a downstream easement.
• Coordinate the stormwater engineer, arborist and landscape designer from concept stage.
• Allow for water quality treatment on multi-dwelling projects, not just detention.
• Confirm current numeric controls with Council before lodgement.

Stormwater Design for Ku-ring-gai Projects

Contrive Consultants prepares tree-aware stormwater and OSD designs for new homes, duplexes and townhouses across the Ku-ring-gai Council area, from St Ives to Gordon. View our stormwater design services or contact the team – call +61 497 848 111 or email info@contriveconsultants.com.au.