RFI - SWMP Elands

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



Table 3.5 Peak flow results from Rational Method with 20% increase in rainfall intensity


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

             63% AEP                  0.022                 0.027      0.005          5
             39% AEP                  0.026                 0.033      0.007          7
             20% AEP                  0.040                 0.050      0.010         10
             10% AEP                  0.049                 0.061      0.013         13
             5% AEP                   0.058                 0.074      0.015         15
             2% AEP                   0.074                 0.094      0.020         20
             1% AEP                   0.087                 0.107      0.023         23



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



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