Swmp

65-67 Elanda Street, Sunshine Beach
Site Based Stormwater Management Plan
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Table 3.4 Peak flow results from Rational Method


        Storm event          Peak Flow Pre-        Peak Flow Post-   Difference   Difference
                              development            development       (m3/s)       (L/s)
                                        3                     3
                                      (m /s)                (m /s)

             63% AEP                  0.018                 0.023      0.005          5
             39% AEP                  0.022                 0.027      0.005          5
             20% AEP                  0.033                 0.041      0.009          9
             10% AEP                  0.041                 0.051      0.011         11
             5% AEP                   0.048                 0.061      0.013         13
             2% AEP                   0.061                 0.078      0.017         17
             1% AEP                   0.070                 0.089      0.019         19



It must be noted that the XPSTORM numerical model and Rational Method are different
methods in nature. Rational method is a mathematical model, which is only recommended
to provide general storm peak discharge without the capacity of considering the infiltration
and runoff storage. Whereas the XPSTORM model is a hydrological model based on runoff
routing technique considering the necessary infiltration and site-specified design storm
events. Higher flow prediction from Rational Method is expected, as represented by Table
3.3 and Table 3.4.

However, both modelling results indicate that the proposed development would cause
similar amount of flow increase. Therefore, it is confirmed that the proposed development
will likely cause flow increases that could create actionable nuisances.




File Name:             WCD-22936 – 65-67 Elanda_SWMP.docx
Revision:              A                                                                       13