Environment & Waste

Flooding Mapping

Flood maps, depicting floodplains in Gosford City, have been produced by council to assist in identifying flooding hazards.

These maps are used by council to define where works may be required and where development controls are required to alleviate the risk to life and damage to property.

These maps also provide vital data necessary for emergency services to identify hazard areas when flood assistance and evacuation may be required.

Council has investigated all the main waterways for flooding and is now investigating the upper catchment areas.

These maps are regularly updated as new flood studies are completed or reviewed.

Common terms

The main flood event that NSW councils use as a benchmark for investigating flooding problems and to set development controls for residential development is the 1% AEP (1 in 100 year) flood event.

This flood event also provides an idea of where major flooding has occurred or is estimated to occur across the Gosford LGA.

However, larger floods above the 1% AEP flood event can occur. The largest flood is called the Probable Maximum Flood (PMF) which is defined as the largest flood that could conceivably occur at a particular location.

Critical infrastructure and other important or vulnerable development, e.g. hospitals, emergency services, evacuations centres, group homes or seniors’ homes, are required to address flooding up to the PMF event.

Flood maps and your property

To assist customers with assessing a property or area of interest, council has provided the 1% AEP flood extent maps for viewing on its website. These maps can be found on the Mapping Page.

These maps show which properties are identified as being affected by a 1% AEP flood event from waterway(s) adjacent to the property. 

However, please note that the depth of flooding may be only minor in some cases (e.g. 150mm) or may be quite high (e.g. greater than 1 metre).

Properties located within or adjacent to the identified 1% AEP flood prone areas may be subject to restrictions on development.

Council is in the process of developing separate maps which will define the Flood Planning Area (FPA) for various waterways, and properties within these areas will be subject to development controls. 

These controls may consist of building to a flood planning level in low hazard areas, maintaining overland flow paths, or more stringent controls in high hazard areas where development is restricted. The FPA may vary according to what waterway is being analysed.

For details of smaller or larger size flood event maps and other data e.g. depths and velocities of flooding, and hydraulic and provisional hazards, customers may view the relevant Flood Study or Floodplain Risk Management Study or Plan.

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