What is a Special Building Overlay?

The Special Building Overlay is a planning scheme provision that identifies areas prone to overland flooding.  The overlay triggers a planning permit for buildings and works (development), with the purpose being to set appropriate conditions and floor levels to address any flood risk to new developments.

Council has prepared Amendment C111 to the Port Phillip Planning Scheme.

The amendment proposes to change the Port Phillip Planning Scheme by:

  1. Updating the Special Building Overlay (SBO) maps to reflect the revised flood extent (land subject to inundation).  This includes depicting SBO1 (areas affected by overland flows resulting from the Melbourne Water main drainage system) and SBO2 (areas affected by overland flows resulting from Council’s ‘local’ drainage system). 
  2. Introducing two new schedules to Clause 44.05 (Special Building Overlay) – SBO1 and SBO2, with Melbourne Water and the City of Port Phillip nominated in the schedules respectively as the relevant drainage authority. The schedules define what permit exemptions apply to specific local areas. These schedules replace the existing schedule to the SBO.

What are the different types of flooding that occur in Melbourne?

Riverine flooding

Riverine flooding occurs when rivers and creeks burst their banks and flow onto surrounding land. This is relatively predictable and can be known hours or days beforehand for major rivers and creeks.

Overland flows

When severe storms generate more water than the drainage system can carry, the excess runs downhill along natural flow paths or valleys. These overland flows usually happen with little or no warning.

This type of flooding is what the Special Building Overlay is designed to address.

Coastal tidal and storm surge flooding

Extreme weather or ocean tides above normal sea levels can flood coastlines and nearby tidal rivers. This type of flooding is usually predictable, but current warning systems do not monitor it.

Sea level rise

Over time, sea level rise caused by climate change will affect coastal properties and low-lying areas. While this happens slowly and is not predictable, we can estimate the future impact.