Attachment D - Stormwater Management Plan · 132008.175.04

              Infiltration Rate (mm/s) = 4mm/sec + 13.6 x head (m)
              Refer to Appendix C for prototype test results.

              In order to model the operation of the RIP’s, a spreadsheet has
              been developed and utilised for all previous stages of Settlers
              Cove.

              Temporal patterns for Zone 3 from the Australian Rainfall and
              Runoff, Volume 2 were applied. These temporal patterns were
              used in conjunction with the average rainfall intensities for the
              Noosa region to create a series of design storms of varying
              duration for a 100-year average return interval (ARI).

              Temporal patterns were converted to flow rates by breaking
              each storm event into a series of short duration storms. A
              triangular flow verses time approximation was used for each
              sub storm with sub storm flows then added to produce flow Vs
              time for RIP inflow.

              Outflow and water depth were then calculated through
              iterations for the duration of the storm based on the infiltration
              rate / head relationship discussed above. A factor of safety of
              2.0 was applied to the observed prototype infiltration rate. Each
              RIP was then sized to prevent overtopping in a 100-year ARI
              storm event of any duration.

              Spreadsheet model results for each building are attached in
              Appendix D.




       6.2    Emergency Overflow (>100year ARI events)

              Emergency overflow, for events (>Q100) which cannot be
              wholly infiltrated by RIPs, is to be directed to the POSCWP area
              as controlled sheet flow at velocities/depths which will not
              induce significant scouring.

              In order to achieve this outcome RIP’s are to be aggregated in
              discrete basins adjacent the POSCWP areas and behind existing
              boulder retaining walls. Stone pitched weirs 3m long and at a
              constant height 0.2m below surrounding bunded area will
              control emergency overflow into the POSCW. The rough nature


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A6107/L9/SMP/RevA/Aug 2021                                                   Page 5 of 7
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