Floodplain aerial view
A floodplain is a low-lying area, often near or surrounding rivers and creeks, that is subject to flooding during periods of heavy rainfall or high-water flow. Floodplains are managed well when development is regulated to protect flood resilience and by using flood maps to inform residents and developers about property risks.
Defined Flood Event (DFE)
A Defined Flood Event (DFE) is a flood of a certain size that has a set chance of happening each year. On the Gold Coast, we have a 0.5% chance of a DFE each year. We manage flood risk by using this DFE to guide safe planning and building in areas that can flood.
Defined Flood Level (DFL)
The Defined Flood Level (DFL) illustrates how high floodwaters are expected to rise during a Defined Flood Event (DFE). If your property is in a flood area, knowing the DFL is important. If you are planning new buildings or renovations the DFL can help you to make sure floors are raised enough and so your property is more resilient to flooding.
Flood Planning Level (FPL)
The Flood Planning Level (FPL) is a safety margin above the Defined Flood Level (DFL). It adds extra height — usually 30 to 50 centimetres — to protect against things like bad weather, blockages, or mistakes in forecasts. We use the FPL to make sure buildings are raised high enough to stay safe during floods.
Floodway
A floodway defines where significant volumes of water will flow during a flood. They are often aligned with natural watercourses and include areas that can experience a significant inundation or redistribution of water, even if water flows are only partially blocked. A floodway can potentially impact neighbouring properties.
Flood storage
Parts of the floodplain that temporarily hold floodwaters are defined as flood storage. Development that substantially reduces this storage – such as filling or levees – can impact surrounding areas by increasing peak flood levels or flow rates.
Flood fringe
A flood fringe is the area that is affected by flooding after the floodway and flood storage areas reach capacity. Development in the flood fringe usually doesn’t significantly impact flood levels or the pattern of flood flows.