stormwater mgJ00300R1V1_25_Kauri_St_Cooroy_Complete · MCU18/0165

25 Kauri St Cooroy




Table 4-6 Detention Storage Details

   Storage Details

74m2 of underground tank storage with a depth of 0.75m                               55.5 m3 storage

125m2 of active flood storage in basin with a depth of 350mm (above the
                                                                                     44.5 m3 storage
extended detention zone)

Total detention storage up to peak 1% AEP flood level                                100 m3 storage

   Outlet Details

Orifice with invert at base of pit                                                 240 mm diameter

High flow weir 1.2m above pit invert level                                         900mm wide weir



Under this configuration the peak flood depth predicted in the basin for the 1% AEP is 1.35m
above the base of the outlet pit (i.e. above the orifice invert level). Assuming the pit invert level is
106.2 m AHD then the peak 1% AEP level in the basin will be 107.55 mAHD.

The storage curve assumed for the WBNM modelling is provided in Appendix D. There is
potential to revise the configuration of the storage basin when detailed design is carried out in the
future. When this is done, the storage in the basin should achieve or exceed the storage curve
assumed for this modelling.

The peak 1% AEP flow rate over the weir is predicted to be 0.08m3/s. This equates to a depth
over the weir of 100mm and velocity of 1m/s. This gives a depth-velocity product of 0.1m2/s
which is a low hazard.

The adopted ensemble hydrograph for each AEP event is shown on Image 4-3. Peak flows and
the associated critical storm duration are also labelled. These hydrographs represent the design
storm runoff from the full mitigated developed site.




J00300R1V1                                                                                           9