Planning Scheme Overlays
Melbourne Water, in conjunction with local councils, prepares drainage survey and floodplain data to be included in the various council planning schemes. Inclusion of planning scheme overlays ensures that drainage issues are addressed at the outset of the development process and that proposals are designed accordingly.
What is an overlay?
An overlay is a map in a planning scheme that shows the location and extent of special features, such as where land may be subject to flooding.
In the case of flooding, overlays are an important way to manage development in order to minimise the effects of overland flows and flooding on new buildings and ensure new development does not adversely affect other existing properties.
Overlays are based upon the extent of flooding that would result from a 1 in 100 year storm. The 1 in 100 year storm relates to a storm event of such intensity that, based upon historical rainfall data, has a probability of occurring once in every one hundred years, or a 1% chance of occurring in any given year.
Types of overlays
Special Building Overlays 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 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 apply to land which is identified as carrying active flood flows associated with waterways and open drainage systems. This overlay is categorised by depths in excess of one metre.