Amended Stormwater Plan · MCU18/0019

SC7440 – Goodchap St, Noosa                                                                              12




4.3.5     Outlet Condition
The subject site is not impacted by regional flooding, refer Section 5.0. The Val Crescent gully inlets have
been modelled with an assumed upstream catchment to estimate the HGL rise through the different storm
events.


4.3.6     On-Site Detention
It is calculated from the development site plan that the proposed development will increase impervious
areas on the site from 24% to 72%. The proposed increase in impervious areas has the potential to
increase peak flow rates to the existing drainage system. To mitigate potential increases in flow rates it is
planned to detain stormwater flows on-site and discharge at a mitigated rate to the existing swale.


Mitigation of flow is provided by the following volume:
          Approximately 225kL of total detention volume within an underground tank. Flows from this storage
          volume will be throttled by a reduced cross-sectional area connection at the outlet (2/225mm), and
          high level overflow pipes. Refer to Figure 4.1 for the detention tank details modelled.




                                   Figure 4.1 – Detention Tank Parameters