2018-11-06 Planning & Environment Committee Agenda

PLANNING & ENVIRONMENT COMMITTEE MEETING AGENDA                                6 NOVEMBER 2018


      Specific Outcome O20
      Development does not compromise the safety of people resulting from residual flood risk
      associated with events that exceed the defined flood event, up to and including the
      probable maximum flood
      Disaster Management O24
      Development supports, and does not unduly burden, disaster management response or
      recovery capacity or capabilities.
Council’s Development Engineer has reviewed the proposed use of a basement car park and
advises that the submitted engineering comments/plans indicate that it is not possible to
construct an access driveway to the basement that achieves the 1%AEP flood level immunity
without significantly impacting on the design due to the road/site levels and the location of the
sewer main that crosses the site to the rear of the basement. It is noted that the flooding in the
area of the site is essentially backwater (Flood Certificate dated October 2017 indicates velocity
of flood waters to be up to 0.5m/sec) and the site is not affected by wave and wind action
compared to a site on the river front.
To address the potential for flood water entering the basement the applicant proposes to install
an automatic flood barrier across the basement access driveway. The type proposed is a flood
barrier that uses the rising flood levels and the associated hydraulic differential to activate the
barrier and raise it into position. The type of barrier proposed does not require power or human
intervention to raise or lower the barrier.
It is considered that the barrier proposed does achieve:
The Noosaville Locality Code - Specific Outcome O17 (a) and (b)
The Residential Uses Code - Specific Outcome O8
The Natural Hazards Overlay Code – Specific Outcomes O17 (a), (b) and (c) and O20
The proposal also includes a grated drain and storage tank at the base of the driveway to collect
runoff from rain that falls on the driveway. The proposal is to pump from the storage tank up to
the Mary Street road formation. The proposal does not include a backup power source for the
pump. The submitted engineering comment indicates that there is potential in the event of a
prolonged power failure for the basement floor area to be inundated to provide extra storage. For
example if 500mm of rain was to fall during a power failure the basement floor would have a
depth of 53mm.
It is noted that other uses are proposed at the basement level (lift, communal laundry and
storage/data/comms). These areas may be inundated should the pump system not function.
It is recommended that conditions be included for the storage tank to have the capacity to cater
for the runoff from a 1%AEP event on the driveway and to include a backup power source for the
pump.
The proposed development does not include a stairwell from the basement to the upper floor.
There is concern that, should the barrier and pump system fail during a significant rain event, any
person in the basement will be trapped putting their life at risk. It is recommended that an internal
stairwell connecting the basement to the upper level be provided. It is considered that the
inclusion of the stairwell would address these concerns and achieve compliance with The
Residential Uses Code - Specific Outcome O8 and The Natural Hazards Overlay Code - Specific
Outcome O17 (a) and (c).
Overlays
The Natural Hazard Overlay applies to the site, Flood Hazard and Acid Sulfate Soils. The issues
relating to flooding have been addressed in the ‘Basement’ section of this report. The
recommendation includes relevant conditions to address acid sulfate soils.



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