2014-08-19 Planning & Organisation Committee Agenda - Pages 1-101

PLANNING & ORGANISATION COMMITTEE MEETING AGENDA                                 19 AUGUST 2014


Legal advice suggests that council should be taking climate change into account when planning
for flood hazard. The current planning scheme includes a 300mm sea level rise for the Noosa
River flood hazard area based on modelling prepared in 1996. Experts advise that this region
could expect sea levels to rise as much as 800mm by 2100 and an increase in extreme weather
events including more severe and frequent flooding.

The amended mapping is based on a 1%AEP (Annual Exceedance Probability) flood event
(Q100) and adopts an 800mm sea level rise and 20% increase in rainfall intensity by the year
2100. These mapping amendments increase the extent of the area shown as being potentially
affected by flooding for the 1% AEP flood event. Larger, less frequent flood events will inundate
land beyond these extents.

If adopted, the mapping would also increase the height properties are required to be developed
to achieve the desired flood standard of immunity. To compensate for the increased flood height,
it is proposed to reduce the freeboard for minimum habitable floor levels for dwellings from
500mm (or 800mm for new development close the Noosa River) to 300mm. This will amount to a
modest overall increase in flood level of around 300mm in some areas. This means that the
habitable rooms such as bedrooms, kitchens and living rooms of new or extended properties in
these areas may need to be built 300mm higher than currently. This additional floor height is
considered to be readily achievable through appropriate design and site layout.

The 300mm freeboard is considered an appropriate safety factor given the conservative climate
change allowance. This approach will ensure the desired level of flood immunity of new
development is preserved for the life of the asset (say for the next 50 years) and will provide
important preparatory action to reduce Council and the community’s flood risk exposure.

By taking into account predictions for future sea level rise, in the short term this will provide an
additional level of flood immunity to new/redevelopment, enabling those developments to
possess greater resilience to extreme events.

As currently, the revised mapping would trigger assessment against the flood provisions in the
natural hazards code and would only apply to applications for new development, extensions over
50m2 and redevelopments.

Various changes are proposed to the flood provisions in the natural hazards code to ensure—
   development provides for an effective evacuation route or safe refuge areas on site;
   development does not alter the flood characteristics external to the development site based
     on current and future climate conditions;
   buildings are designed to provide for an attractive street front address appropriate to the
     intended use; and
   building materials used below the defined flood event have a high water resistance.
New definitions are proposed to be added to Part 2 Interpretation as follows:

defined flood event means the event, measured in terms of the likelihood of occurrence, and
associated inundation level adopted by the Council to manage development as identified in Table
13.12 (Flood levels and flood immunity requirements) of the Natural Hazards Overlay Code. The
DFE incorporates an allowance for future climate change over the design life of the development,
through increased rainfall intensities, mean sea level rise and a greater frequency of extreme
weather events.




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