MCU14/0056 Stormwater Quantity Management Plan Att D Information response

6.0     CONCLUSIONS
      This report has been prepared to address the stormwater and flooding issues raised in the
      Main Roads and Noosa Shire Council’s Information Request Letters. A direct response to
      each item in these information request letters is presented in Section 2.0.

      The existing site is undeveloped and contains a waterway which traverses along the eastern
      side of the site. The proposed development involves the construction of a multi-use facility.
      This development includes a service station with a fast food drive thru outlet, a car wash
      facility, a self-storage unit facility and a caravan tourist park which includes 10 cabins and a
      pool.

      An URBS hydrologic analysis was undertaken to determine effects of the development
      through the subject site. The URBS model results show a minor increase in peak flows
      downstream of the site during a Q1, Q5 and Q10 storm event; however reductions are seen
      during a Q20, Q50 and Q100 storm event. The URBS results show a net marginal benefit. The
      nominal storage in the bio retention will attenuate the frequent low flows. Therefore it is
      considered that a detention basin is not required.

      A 1D HECRAS hydraulic model was setup to determine the inundation extent through the
      site. Figures 7 and 8 in Appendix A illustrate the 1% AEP flood extent for the existing and
      developed site. The results indicate that the proposed development will not result in an
      adverse impact on neighbouring properties and roads.




      Darren Rogers
      BE Civil (Hons), MIE Aust, RPEQ
      Director




                                        J4279 Report 1.0.doc
                                          14 January 2015                                     Page 14