If you are intending to build a dwelling on a property with a LSIO or FO, a Council Report and Consent is essential. This request to build on land subject to inundation is referred to the relevant water catchment authority, who will either grant approval for a building permit to be issued or refuse depending on the area of inundation on the property.
A Report and Consent Application form for Regulation 153, with the required documentation and applicable fee, can be submitted through Council's online building portal here. Registration for the portal is only required once (refer to the Building Forms page for the Report and Consent application form).
See the updated Victorian Building Authority's Practice Note: PN-65-2018-Flood-Hazard-Areas-and-Building-Regulations.pdf