RFI - Stormwater Mgm Plan 20169 - SBSMP - Rev 4 (2)

                                                                                 20169 - SBSMP/4
                                                                                          Page 14




The XPSTORM hydraulic modelling shows that the water level does not exceed the emergency weir
level in the northern basin and a freeboard of approximately 33mm is maintained. As can be seen
when comparing flows between Table 5-5 and Table 5-6, pre-development flows are still maintained
for Catchment B. There is also a 300mm wide gap between the boundary and the basin wall where
emergency overflow will fall onto natural ground level prior to sheet flowing across the boundary.
Therefore, pre-development drainage conditions are not expected to be worsened for the
downstream properties within Lot 79 and Lot 80 on SP138388, northeast of the site.

Furthermore, the downstream pipe capacity analysis for each legal point of discharge has taken
into account a tailwater condition of 150mm below surface at the stormwater gully pits located
within the road reserves, which is considered a conservative measure.

Therefore, XPSTORM hydraulic modelling has demonstrated that the proposed mitigation
implemented will still maintain pre-development flows (or less) for the 1% AEP storm event at end
of planning period 2100 at the aforementioned LPDs.




Site Based Stormwater Management Plan
Proposed Townhouse Development at 99, 101 & 105 Eumundi Noosa Road, Noosaville