The PMF is the largest flood that could conceivably occur. It is typically estimated from probable maximum precipitation coupled with the worst flood producing catchment conditions. While it is a rare and improbable occurrence, every property potentially affected by a PMF is considered to be on a floodplain and has some element of flood risk. Under the State Government's Flood Risk Management Manual (2023), councils must consider the full range of risk when managing floodplains.

A 1% AEP flood event (often referred to as the 100-year flood) is the flood that has a 1% probability of occurring in any given year. If you have experienced a 1% AEP flood event, it is still quite possible for you to experience another event of similar magnitude within your lifetime, as large flood events do occur randomly. Some parts of Australia have received two or three 1% AEP flood events within a few years of one another. On average, if you live to be 70 years old, you have a greater than 50% chance of experiencing a 1% AEP flood event.

Australian Height Datum is a reference of the elevation of any object or point above mean sea level, which is taken as 0m AHD. All flood levels, floor levels and ground levels are given in meters AHD.

The NSW Government's Flood Risk Management Manual (2023) outlines the required method for councils to manage flood liable land. A key objective in this manual is to undertake flood studies for appropriate catchments to provide detailed information on flood behaviour.

Council has completed a number of Flood Studies and Flood plain Risk Management Studies. The adopted studies are available on Council's website. If your property is flood affected and you require flood levels and velocities for your property, you can submit a request for flood level information to Council. Council will then provide you with property specific flood information letter that can be used to manage your risk and inform the design of your development proposal.

You can request flood information via the following link: https://www.shellharbour.nsw.gov.au/council/forms/...

Flood behaviour, including flood levels, velocities and hazard is calculated using detailed computer models to simulate floods of varying magnitudes. These models may be reviewed periodically when:

• new data becomes available from new flood events
• flood mitigation works are undertaken
• developments occur, and
• more advanced computer models become available.

Many parts of Shellharbour City have little or no flood data or records available at Council. Over time as new data is received and new flood studies are adopted by Council, more flood liable land will be identified and mapped accordingly. Also, under the NSW Government's Flood Risk Management Manual in (2023), flood liable land became inclusive of land that is affected by the Probable Maximum Flood (PMF).

If your property is now classified as flood affected, the real world flood risks to your property is not likely to have changed; only that new information has been made available.

No evidence has been presented to Council to suggest that there have been negative impacts on property values or development in study areas. Councils floodplain management program has been ongoing now for more than 20 years. Council first adopted a flood study for Lake Illawarra in 2001. A flood study was adopted for Elliot Lake Little Lake in 2006 and again for Horsley Creek in 2011. Concerns over effects on property values were raised from residents in these catchments prior to adoption by Council.

In 2012, a standard definition of flood was agreed upon by the Insurance industry. This is now known as:

The covering of normally dry land by water that has escaped or been released from

the normal confines of:

• any lake, or any river, creek or other natural watercourse, whether or not altered or

modified; or

• any reservoir, canal, or dam.

However, Insurance companies each have their own distinctive ways in which they calculate risk and determine insurance policy premiums. Many insurance companies will offer house and contents insurance, with each individual insurance company determining their own policy and conditions.

Flood insurance premiums generally reflect the level of flood risk at a property and the cost of repairing or rebuilding the property. In practice, this can be broken down to three factors which would be assessed by all insurers when setting a flood premium for a property:

• Likelihood of flooding;
• Expected depth of flooding relative to the insured building; and
• Expected cost of recovery.

Likelihood and depth of flooding are assessed at an individual address level, using results from computer flood modelling which simulates how water flows through a catchment. Expected cost of recovery includes repair, rebuild and replacement costs, temporary accommodation, and other factors such as the potential shortage of materials and labour after a flood event. Some insurers may also consider property-specific information such as number of storeys, floor levels, building materials used and construction type.

Insurance policies and conditions may change over time or between insurance companies, and you should confirm the specific details of your situation with your insurer.

Floodplain Management Australia has developed flood insurance fact sheets to assist property owners in understanding the information surrounding this process.

Flood affected properties may be developed if the proposed development meets the relevant standards and requirements. The applicable planning controls are largely determined by the proposed land use and the extent of flooding on your property.

A Local Environmental Plan (LEP) is a legal document which allows Council to regulate land use and development. They are prepared by Council and approved by the State Government.

A Development Control Plan (DCP) provides detailed planning and design guidelines to support the planning controls in the LEP. Sections of Council's DCP provide criteria for assessing applications for properties potentially affected by flooding. The above documents are available on Council's website.

Council owns and manages a significant number of stormwater pits, pipes, channels, culverts, basins and Gross Pollutant traps throughout the city and we are committed to maintaining this infrastructure within the limits that current funding and resources permit. Council has an annual budget for cleaning and maintaining this infrastructure, as well as a budget for Capital Works (upgrading and building new infrastructure). All works are scheduled on a priority basis, where those works that are most critical become highest priority.

Although the impact of vegetation on flood behaviour is very important, vegetation has an essential function in managing erosion and providing habitat to wildlife. Unless identified within an adopted Floodplain Risk Management Study & Plan, the flood impacts associated with the removal of vegetation from creeks and waterways is relatively unknown. For example, carrying out such works may have little to no benefit in reducing flood risks. Alternatively, such works could reduce the flood risks in one area, whilst increase it in other areas. These issues are considered in the context of a Floodplain Risk Management Study.

Within the Horsley Creek catchment, a large proportion of the creeks and waterways are also within private property, and as such Council is unable to maintain these areas.