Brief description

The main objective of this study (in two parts) has been to determine water levels in Brisbane Water for
the full range of flood and ocean events that can occur due to the various natural physical
processes, taking joint occurrence issues into account to some extent. The flooding
behaviour can be influenced, either separately, or by a combination of, catchment rainfall
runoff flooding, rainfall directly onto Brisbane Water, elevated ocean levels, local winds
and, to a minor extent, the condition of the ocean entrance channel near Ettalong.

The outcomes from this study include: -

* Public Participation: Community consultation is highly important in the whole process
leading to the development of a sustainable floodplain risk management plan and is an
essential component of the flood study. An information leaflet and questionnaire were
prepared and delivered to residents, whose properties were considered to be lower than
2.5m AHD (see Figure 4.2) and potentially at risk of inundation.
* Brisbane Water Design Foreshore Flood Levels: This Study has determined design still
water levels and flood extents for a full range of flood events for existing catchment
conditions. All contributing physical processes of wind, rain, waves and tide were
considered. Cardno Lawson Treloar, as part of the Brisbane Water Estuary Processes
Study, have set up and calibrated hydrologic and hydrodynamic models of the catchment
and waterway, respectively, as well as fine grid wave models of sub-regions of the
waterway. This calibration process involved some months of work and hence having these
models ‘ready-to-go’ helped the study schedule.
* Hydraulic and Hazard Categorisation: To achieve effective and responsible floodplain
risk management, the Brisbane Water floodplain was divided into areas that reflect the
different hydraulic impacts of development activity on flood behaviour and the hazard
impact of flooding on development and people.
* Floodplain Risk Management Measures: This study forms the basis for a future Brisbane
Water Foreshore Flood Risk Management Study and Plan, where detailed assessment of
flooding risk management measures and a damages assessment will be undertaken for all
urban settlements along the foreshore of Brisbane Water. Cardno Lawson Treloar have
undertaken many Floodplain Risk Management Plans and undertook this study keeping
those future needs in mind.