Appendix E - Stormwater Management Plan · MCU22/0140

                                                                                                             ingeniir

Detailed Erosion and Sediment Control design and plans should be documented by a suitably experienced
professional in conjunction with any application, or prior to commencing with the Operational Works
associated with the proposed development on site.


5.2         Operational Phase

The site has an allotment area of 1012m2 and as such does not trigger local or state requirements for
operational treatment objectives for stormwater quality.

The above ground rainwater retention tanks will provide opportunity for nutrient retention on-site and it is
proposed that the tanks will be used for landscape irrigation and other external uses. In context of the scale
of the development the re-use of rainwater on site is considered an acceptable outcome.


6.      STORMWATER QUANTITY
The development is proposed to incorporate stormwater detention to mitigate the increase in peak discharge
from the site.

The Bureau of Meteorology 2016 IFD service has been used for all analysis in this report.

A Rational Method estimation of the stormwater discharge has been used to estimate the pre-developed
runoff performance of the site. The detention analysis has been proportioned to match or improve on the
pre-developed flows as determined by the Rational Method. A summary of the Rational Method discharge
estimations are presented in Table 1.


 DISCHARGE ESTIMATES ( m 3 / s)
                                  Pre-Developed Flow Rates                                         Developed Flow Rates
      AEP        Rational Method                    WBNM                         Difference           Rational Method
 63.20%                0.02                         0.021                        0.001 (105%)                0.022
 39.35%               0.027                         0.029                        0.002 (107%)                0.029
 18.14%               0.038                         0.039                        0.001 (103%)                0.04
     10%              0.046                         0.049                        0.003 (107%)                0.048
      5%              0.054                          0.06                        0.006 (111%)                0.058
      2%               0.07                         0.067                        -0.003 (96%)                0.074
      1%               0.08                         0.074                        -0.006 (93%)                0.085
                                    Table 1: Rational Method discharge estimation for the site

A WBNM 2017 (v001) hydrology model has been used to determine the detention volume required to
maintain or improve on the current flow characteristics of the site. Temporal patterns from ARR2016 have
been used in the analysis, along with reference parameters from the ARR Data Hub.

The WBNM pre-developed model was calibrated to achieve an acceptable alignment with the existing site
Rational Method estimates for whole of site discharge.




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