Site Based Stormwater Management Plan

4.5    Pre-Development v Post-Development Flow Comparison

Table 4.4 below compares the pre-development Rational Method results from Section 4.2,
with the post-development XPSTORM model results from Section 4.3 to demonstrate the
requirement for stormwater detention.


                                   Peak Discharge Comparison (m3/sec)
                        Pre-Development        Post-Development
   Design Storm                                                          Difference        % Change
       (AEP)            Rational Method            XPSTORM


       63%                    0.089                  0.125                 0.036             40%
       39%                    0.114                  0.160                 0.046             40%
       18%                    0.158                  0.223                 0.065             41%
       10%                    0.198                  0.279                 0.081             41%
        5%                    0.236                  0.333                 0.097             41%
        2%                    0.301                  0.413                 0.112             37%
        1%                    0.346                  0.456                 0.110             32%
       Table 4.4 Pre-Developed Rational Method v Post-Developed XPSTORM Peak Stormwater Discharge



From Table 4.3 the proposed development will increase peak flows discharging from the
site, therefore stormwater mitigation will be required to demonstrate post-developed
stormwater discharge is consistent with pre-development characteristics in accordance with
the Noosa Plan (2020).




Site Based Stormwater Management Plan                                                       Page 7 of 19
2123-SBSMP-01_Version 1.0 (October 2021)