Flood Risk Management

Floods are one of the most expensive natural hazards experienced in Australia. There has been evidence of this over the last 36 months, where major floods have hit communities on Australia’s east coast which resulted in millions of dollars worth of damage to private properties, as well as public infrastructure and that majorly impacted the national economy.

Flood behaviour is influenced by a range of factors, including the speed of conversion from rainfall to runoff and the floodplain topography. Depending on location, these factors affect flood risk differently which needs to be understood and managed locally.

Flood Risk

Flood risk at any location varies due to the frequency of flooding and the consequences the community suffers. Flood risk management mainly involves reducing the impact a flood causes on people in the community and the impact that affects both public and private infrastructure.

Due to ever changing conditions and demographics, having updated and accountable flood risk management plans in place is essential. Conditions such as the uptake in urban expansion along with changes in flood behaviour, as well as the influence of climate change affecting rainfall patterns and the rising sea level produce more exposure to potential flooding incidents. This is why it is so important to have effective flood risk management plans in place because without said plans, people, property, local industry and economies the potential impact would exponentially increase.

Flood risk management has significantly evolved over the past 70 years to reduce the catastrophic impacts communities suffered. In the 1950s, the main focus of a risk management plan was to reduce risk through mitigation works as they were cost effective. Today, an effective risk management strategy requires heavy consideration of existent and future communities, as well as a combination of the following options.

Reducing the community’s exposure to flood risk

For existing communities this may mean that structural flood mitigation measures need to be taken. Measures such as protecting the existing development from flooding with levees, detention basins that reduce downstream flows or increasing water flow capacity in the floodplain. When these types of measures are proposed, it’s important that careful consideration is given to determine any possible environmental impacts. The measures made need to be sustainable and effective. It’s also important to note that careful consideration needs to be given to potential environment enhancement as part of every flood risk assessment.

For families and communities looking to occupy new land in hazardous and potential flood risk areas, effective planning can limit the amount of damage previously experienced. Using land use planning in addition to developing an effective subdivision layout and a strategic development plan can help combat the potential risks of a flood. One of the most common strategies that has been implemented in urban areas is to set minimum floor levels. Another application that can be used to restrict certain types of development is land use zoning.

Structural measures, and sometimes land use planning regulations, require a threshold beyond which they no longer offer protection and is typically associated with flood frequency. This standard should ideally be set through community consultation, ensuring that it is both acceptable and affordable. It’s also important to account for scenarios where this standard is surpassed.

Reducing the vulnerability of communities and properties to flood risk

To reduce the potential exposure for existing communities, options like voluntary house raising in less hazardous areas can reduce the frequency of flood damage.

For all communities, reducing the vulnerability of people and property involves a combination of:

• The ability to financially recover after a flood event
• Appropriate technical specifications for buildings
• Availability of infrastructure
• Flood awareness and readiness
• Flood forecasting and warning
• Flood response assistance
• Insurance being an important tool in a community’s recovery

For future communities, it is essential to consider the potential vulnerability of future occupants when implementing land use planning and development controls. An acceptable level of risk for the general population may not be acceptable for the elderly population. Therefore, facilities such as aged care homes, hospitals, or other buildings serving more vulnerable members of the community should not be located in flood-prone areas if evacuation is difficult, flood warnings are inadequate, or the facilities cannot be evacuated in time.

The complexity of floodplain management today underscores the necessity of integrating diverse skills and disciplines such as floodplain management, civil and water engineering, hydrology, hydraulics, emergency management, land use planning, research, policy making, and insurance. Effectively leveraging these skills and securing the funding required for expensive solutions depends on the support and cooperation of all levels of government and various government departments and agencies.

Flood Risk Management is essential to understanding flood risk and flood behaviour. For an effective flood plan, the responsibility falls not only on government institutions but the local communities as well. To effectively implement these important strategies, explore the Flood risk management toolkit on the NSW Government website. All parties involved need to be on the same page when it comes to the warning and response to floods, ensuring that everyone is safe and accounted for. To learn more about your local flood risk management plan, take a look at NSW Government’s Floodplain management plans.