Swmp

They are as follows: -

       Pit Number                HGL(Exist)               HGL (Prop.)                  S.L. (m)

            H5                       6.43                      6.46                      8.34
            H4                       4.54                      4.57                      6.29
            H3                       3.54                      3.76                      4.08
            H2                       2.96                      3.13                       4.0
            H1                       1.71                      1.78                      2.51



The above results confirm pit number H3 as having the greatest increase in the HGL level of 220mm.
However, there is still 320mm of freeboard within the pit which is in accordance with QUDM minimum
freeboard depth of 150mm.

Catchment A will result in a increased discharge to the Eumundi Noosa Road kerb and channel, however
this has been limited to a Q10 flow rate of 25Lt/s at each kerb adaptor location as per Noosa Council
requirements. The net total discharge from the proposed site will remain below pre development flows
for all storms from Q1 up to Q100.

6.4      Climate Change Analysis for 1% AEP Storm Event at Year 2100
A climate change analysis has been undertaken to determine the impact for a 1% AEP storm event at
year 2100. This includes a 20% increase in rainfall intensity to allow for climate change. As part of the
Climate change analysis, runoff flows were increased by a factor of 1.2 to incorporate a 20% increase
to rainfall intensity.

The PC DRAINS Results displayed in Table 6.7 maintain pre-development flows for catchment C 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.

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




SCG Consulting Engineers                    Page 21                               SCG Ref: 33132(SWMP)