Attachment D amended SWMP

5.5.4     Pre- and post-development (with mitigation) peak flow rates comparison
The table below summarises the pre- and post-developed (mitigated) design flow rates off the Development
Area.
Table 6- Comparison of Pre- and Post-Development (Mitigated) Peak Flow Rates

                                    Q1          Q2          Q5          Q10
                                                                                   Q20         Q50         Q100
                        Area       (63%        (50%        (20%        (10%
                                                                                (5% AEP)    (2% AEP)    (1% AEP)
                        (ha)       AEP)        AEP)        AEP)        AEP)
                                                                                  (m3/s)      (m3/s)      (m3/s)
                                  (m3/s)      (m3/s)      (m3/s)      (m3/s)

 Development Area
                        0.415     0.059       0.086       0.112       0.140       0.167       0.198       0.220
  (Pre-Development)

 Development Area
                        0.415     0.058       0.073       0.111       0.129       0.154       0.183       0.207
  (Post-Development)

        Increase                  0.001       -0.013      -0.001      -0.011      -0.013      -0.015      -0.013
                                  (-2%)       (-13%)       (-1%)       (-8%)       (-8%)       (-8%)       (6%)


Results show that after mitigation, compared to existing condition, there is no increase in post-development design
flow rates for the development area.

Table 7 - Comparison of Pre- and Post-Development (Mitigated) Peak Flow Rates (Climate Change)

                                    Q1          Q2          Q5          Q10
                                                                                   Q20         Q50         Q100
                        Area       (63%        (50%        (20%        (10%
                                                                                (5% AEP)    (2% AEP)    (1% AEP)
                        (ha)       AEP)        AEP)        AEP)        AEP)
                                                                                  (m3/s)      (m3/s)      (m3/s)
                                  (m3/s)      (m3/s)      (m3/s)      (m3/s)

 Development Area
  (Pre-Development      0.415     0.080       0.110       0.150       0.179       0.207       0.244       0.270
 20% Climate change)

 Development Area
  (Post-Development     0.415     0.072       0.106       0.148       0.169       0.202       0.233       0.270
 20% Climate Change)

        Increase                   0.008      -0.04       -0.002      -0.010      -0.005      -0.011      -0.000
                                  (-10%)      (-4%)        (-1%)       (-6%)       (-2%)       (-5%)       (0%)


Results show that after mitigation, compared to existing condition, there is no increase in post-development design
flow rates for the development area with the climate change increase included.




 BR210522_SBSMP_Rev5.docx                                                                                   Page 11 of 25