Volume 1 Report This flood study has been undertaken to determine the flood behaviour in the catchment due to local storm runoff for the 0.5% Annual Exceedance Probability (AEP), 1% AEP, 2% AEP, 5% AEP, 10% AEP, 20% AEP, 50% AEP and 100% AEP flood events and the Probable Maximum Flood (PMF). In accordance with its objectives, the study has determined the nature and extent of flooding through the estimation of design flood flows, levels and velocities. Flood impacts due to storm events in the Brisbane Water estuary are detailed in the Brisbane Water Foreshore Flood Study (2009). In undertaking the flood study, a hydrologic-hydraulic computer model of the major channels and floodplain within the catchment was established and verified against historical flood event observations. The hydraulic model was then used with design rainfall conditions to simulate design flood behaviour in the catchment. The study has defined Provisional Flood Hazard and Hydraulic Categories for the flood affected areas.

The objective of this Study is to define the nature of the existing flood behaviour due to local runoff only in the Davistown catchment.

To achieve the objectives, the following tasks were undertaken:

• Collate available flood-related data,
• Define existing catchment condition flood behaviour for mainstream flooding in the catchment,
• Define design flood levels, velocities and flow distributions for the catchment,
• Define the extent of flooding the nominated AEP events and PMF for the catchment,
• Define the hydraulic categories for the flood-affected areas,
• Define provisional flood hazard for the flood-affected areas,
• Assess flood damages for the flood-affected areas.