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What is Flood Assessment Report

When planning to develop a project, the council will require you to present a Flood Assessment Report if the site is in a flood-prone area. This report assesses the flood risks of the site and suggests a plan to counteract these flood hazards. Flood resilient designs involve building alterations that aim to counter the effects of flooding, all while ensuring that the integrity of the original architectural design is kept.

The 1% Flood Annual Exceedance Probability (AEP)

The Annual Exceedance Probability (AEP) represents the likelihood of a flood occurring in an area at any given year. Designers and engineers refer to a 1% AEP when developing a plan. The 1% AEP refers to maximum probable flood which has a 1% chance in a single year. This can also be represented as a ‘1 in 100-year flood’ and must be considered when looking at a site for development.

The 1% Flood Annual Exceedance Probability (AEP)

Common Flood Resilient Designs

Type 1: Elevating Finished Flood Level

  • Raising the level of the building by working on top of existing property.

Type 2: Level for Level

  • Raising the level of the property by filling land beneath the building (most commonly using concrete). To compensate for the new land mass in the floodplain, ‘cuts’ are made around the property to hold water. This prevents raising the floodplain height and affecting buildings around the property.

Type 3: Flood Resistance

  • Raising the upper floor of the building and suggesting design plans for the lower floor to meet water-resistant requirements.


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Useful articles from various government agencies and flood experts

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