Flood-Planning Levels Explained
What a flood-planning level is and how it sets your floor height in the Northern Rivers NSW — the 1% AEP flood, freeboard, and how councils apply it to a build.
If you are building on flood-prone land in the Northern Rivers, the single number that shapes your design is the flood-planning level. It sets how high your habitable floors have to sit, and it is the reason two neighbouring blocks can need very different homes. This guide explains what it is and how it works.
It is general guidance, not advice for your specific block. When you are ready, we confirm the flood-planning level the council holds for your exact address and design to it from the start.
What a flood-planning level is
A flood-planning level (FPL) is the height, above sea level, that your habitable floor must meet or exceed on a flood-prone block. Councils set it from a flood study, usually based on the 1% annual exceedance probability flood (the '1-in-100-year' level) plus a freeboard allowance for safety. The result is a specific height for your land, not a single figure for the whole town, and it is what decides whether a standard slab works or the home needs to be raised.
How it shapes the build
Once the FPL is known, it drives the floor system — a slab-on-ground on higher land, or a raised, suspended floor on piers where the level sits well above natural ground. It also influences where services and electrical go and what materials are used low in the structure. We confirm the FPL for your block early so it is built into the design rather than discovered at the construction-certificate stage, when changing it is expensive.
Questions
- How do I find the flood-planning level for my block?
- It comes from the council's flood mapping for your specific address, derived from the local flood study. We obtain and confirm the flood-planning level for your block before design so the floor height and floor system are right from the outset rather than assumed.
- Is the flood-planning level the same as the 1-in-100 flood?
- Not quite. The flood-planning level is usually the 1% annual exceedance probability flood (often called the 1-in-100-year flood) plus a freeboard margin added for safety, so it sits a set distance above the modelled flood height. The exact figure depends on your council's controls and your block.