Stormwater Management Plan · MCU15/0122

                                                                                         15099 - SBSMP/3
                                                                                                  Page 12




         Table 5.7 - Post-Development Peak Discharge (XP-RAFTS and Rational Method)
                                      XP-RAFTS                            RATIONAL METHOD
             ARI           Post-Development Peak Discharge          Post-Development Peak Discharge
           (years)                  (Unmitigated)                            (Unmitigated)
                                        (m3/s)                                  (m3/s)
                                        0.194
              2                                                                  0.144
                                     (2yr 25min storm)
                                           0.239
              5                                                                  0.198
                                     (5yr 25min storm)
                                           0.266
              10                                                                 0.230
                                     (10yr 25min storm)
                                           0.306
              20                                                                 0.274
                                     (20yr 25min storm)
                                           0.325
              50                                                                 0.346
                                     (50yr 15min storm)
                                           0.359
             100                                                                 0.386
                                     (50yr 15min storm)


As seen in Table 5.5 and Table 5.7 there will be an increase in peak flows between pre and
post-development conditions as a result of the proposed development. Consequently on-site
detention will be required.

5.6.3 Post-Development Mitigated
It is proposed to provide underground detention storage within the southern portion of the site.
The detention storage is to be implemented as part of the internal stormwater drainage
network. The underground detention basin will receive roof water from the total roof area.

Figure 5.2 shows the XP-RAFTS model used to represent the post-development mitigated site
scenario for the proposed development. The model is the same as the post-development
unmitigated model used in Section 5.6.2 above however the detention basin has been added to
receive runoff from the Roof Node. Flows (>Q20) that exceed the capacity of the roof water
guttering and down pipes are diverted directly to the LPD. For explanation of what each node
represents refer Table 5.3.




                      Figure 5.2 - XP-RAFTS Post-Development Mitigated Model




Site Based Stormwater Management Plan
Proposed Medical Development at Cnr Val Crescent & Goodchap Street, Noosaville