2015-03-31 I&S Committee - Item 4 - Attachment 1 - Flood Mitigation Investigation Ashgrove Dr Cooroy

Flood Mitigation Investigation: Ashgrove Drive, Cooroy



                                                          There is potential to modify the channel
                                                          configuration during detail design.


  Material for the construction of the “bund”, as well    Agree - the proposed bund is essentially a flood
  as maintenance aspects related to the bund, need        levee and will require on-going monitoring to ensure
  to be considered (stability, scour potential, long      structural integrity is maintained. Detail design
  term erodibility)                                       channel should address stability, erosion and scour.


                                                          Flood modelling of the current project predicts 1%
                                                          AEP flow velocities are less than 1m/s and
                                                          therefore grass lining or native planting would be
  Is lining of drain required to protect against          sufficient. Some local scour protection may be
  scour/erosion?                                          required at inlet/outlet subject to final detailed
                                                          design.

                                                          To be addressed at detailed design stage.


  Community impacts (if any) need to be considered,
  including consultation                                  Council to Action


                                                          Yes there is likely to be environmental benefits
                                                          however this may be difficult to achieve if a bund is
                                                          excluded from the design.
  Proposed work changes the overland flow path
  regime in this area. Are there benefits from low flow
                                                          Council may wish to assess environmental value of
  events still draining toward Ashgrove Drive?
                                                          the Ashgrove Drive tributary downstream of the
                                                          diversion to determine whether low flow diversion is
                                                          desirable.


  Access needs to be considered to maintain drain.
  Are TMR responsible for maintenance of drain,           Council and DTMR to negotiate.
  considering it is in the road reserve?


                                                          HWMC do not believe extension of the bund is
  TMR would not be responsible for any effects            required. All lots on the eastern side of Cooroy
  caused by surface water levels increases in Cooroy      Creek (i.e. Ashgrove Drive lots) receive an overall
  Creek downstream of the Bruce Highway (afflux           benefit from the works. Land on the western side of
  increases from 10 mm to 25 mm). Note: Could             Cooroy Creek is owned by a developer and it is
  bunding be extended to shield the closest               expected that negotiation with the developer would
  structures/properties to Cooroy Creek.                  be the best option here (noting impacts are over
                                                          land designated as open space / drainage reserve)


  Noosa Shire Council to consult with Ashgrove Drive
                                                          Council to Action
  residents to gauge acceptance of proposal.


  Any resident complaints in regard to loss of
  vegetation or perceived increased noise levels to be    Council to Note
  referred to Noosa Shire Council
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