SCG 31131(SWM).RevA

The PC DRAINS Results displayed in Table 6.7 maintain pre-development flows for catchment B as
displayed in Table 6.5. The Hydraulic modelling shows that the water level does not exceed the
emergency weir level and maintains a freeboard of approximately 100mm. A 300mm gap between the
basin and RP boundary with scour protection has been provided where emergency overflow will fall
onto natural ground level prior to sheet flowing across the boundary. Therefore the hydraulic modelling
has demonstrated that pre-development drainage conditions will not worsen for the Downstream
properties outlined in Catchment B for the 1% AEP storm event at year 2100.



Furthermore, the downstream pipe drainage analysis for the legal point of discharge has used a tailwater
level of 150mm below surface level at the stormwater manhole located in Headland Drive, which is
considered a conservative approach.



Catchment A will result in an increase to pre development flows. However we have assessed the
capacity of the Eumundi Noosa Rd Kerb and channel in accordance with Section 7.4 of QUDM 2017 &
Aust Roads Guide to Road Design Part 5A Section 5.3 using a 3m flow width for the 10 Yr ARI (10%
AEP). Calculations confirm the Kerb and channel can safely convey the proposed post development
10% AEP catchment flows in addition to the existing catchment whist maintaining a 4m wide flood-free
trafficable lane on Eumundi Noosa Rd.




7.0      FLOODING


Information provided from Noosa Council’s Flood Hazard Overlay Map confirms the site is unaffected
by flooding.




SCG Consulting Engineers                  Page 23                           SCG Ref: 31131(SWMP).RevA