There are four types of overlay that mean you may need the consent of a floodplain management authority (such as Melbourne Water) in writing, before you put in your application for a planning permit. This applies to VicSmart applications where the lot is identified under a Special Building Overlay (SBO).
The overlays relating to floodplain management authorities include:
Special Building Overlays (SBO)
These are planning scheme controls that identify areas prone to overland flooding. The purpose of these overlays is to set appropriate conditions and floor levels to address any flood risk to developments. These overlays require a planning permit for buildings and works.
Land Subject to Inundation Overlays (LSIO)
These are planning scheme controls that apply to land affected by flooding associated with waterways and open drainage systems. Such areas are commonly known as floodplains. These overlays require a planning permit for buildings and works.
Floodway Overlays (FO)
These apply to land that’s identified as carrying active flood flows associated with waterways and open drainage systems. This overlay is categorised by depths in excess of one metre.
Urban Floodway Zone (UFZ)
Unlike the overlays, the UFZ controls land use as well as development, with land use being restricted to low intensity uses such as recreation and agriculture. Development is generally not encouraged in the UFZ.
Source: Overlays Explained by Melbourne Water