2019-02-12 Planning & Environment Committee Agenda

PLANNING & ENVIRONMENT COMMITTEE MEETING AGENDA                                 12 FEBRUARY 2019




                                Figure 3 – 1% AEP extent shaded in blue

An existing driveway to access the rear building is located across the overland drainage path which
is not immune to certain rain events particularly during a 1% AEP rain event. Concerns are raised
regarding potential adverse offsite flooding impacts and the ability of residents to enter and exit the
property and to evacuate in major flooding events, compromising the safety of people.
In regard to these concerns, the proposal is to raise the driveway to offset some of the flooding
impacts and the applicant’s hydrology consultant advises the following:
    The flow across the site is an intermittent flow path from Noosa National Park being dry most
      of the time with only trickle flows.
    Only approximately 30% of the total flow from the upstream catchment passes through the
      site with the remaining 70% outside the site and inside the National Park.
    Adjacent the very upstream southern boundary the flow depth beside the existing residence
      in a 1% AEP is 400-500mm deep
    The required flood immunity for detached houses under the Noosa Plan is 300mm above the
      modelled floor level whereas the freeboard provided to the existing residence is 580mm
      above the highest water elevation in the defined flood event on the upper most southern
      boundary, which is compliant.
    The maximum flow depth across the driveway low point is 390mm and the velocity is 1.0m/s
      maximum which complies with Table 7.4.5 from QUDM which requires a maximum depth x
      velocity of 0.45m/s2 and the proposal is 0.39m/s2. The QUDM table limits depth x velocity to
      be less than 0.45m/s2 for vehicle safety at intersections.




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