RFI - SWMP Elands

65-67 Elanda Street, Sunshine Beach
Site Based Stormwater Management Plan
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QUDM-2016 refers to the Australian Rainfall & Runoff (ARR) for guidance on IL and CL. In
Section 3.5 of Book 5 of ARR, recommendations for the IL & CL are adopted. In particular,
the IL value of urban pervious area is suggested to be 10mm – 30mm. The IL value of
effective impervious is suggested to be 1mm – 2mm. Details of the applied IL and CL
parameters are presented in Table 3.2.

Table 3.2 Adopted Initial & Continuing Losses

                   100% Impervious Area                       0% Impervious Area
                 IL (mm)                CL (mm/hr)         IL (mm)        CL (mm/hr)
                    1                       0                10               2.5



3.2 Modelling of Peak Discharge and Impact Assessment
Through the analyses of hydrological model, it is identified that the worst-case storm
duration is 25 minutes for both Minor (10% AEP) and Major (1% AEP) storm events, as
shown in Appendix C. Therefore, 25 minutes is consistently adopted as critical design storm
duration for storm events ranging from 63% AEP to 1% AEP.

To identify the flow increase due to the development, the Pre- and Post- development
scenarios are modelled simultaneously with the same infiltration parameters across various
of rainfall events.

Hydrographs of 25mins storm events for various of storm events are summarised in Figure
3.1. It can be observed that with the increase of AEP the flow increases consistently for both
pre- and post- development scenarios.

To further assess the impact due to the proposed development, the peak flows of storm
events with various AEPs are extracted from Figure 3.1, as shown in Table 3.3.




File Name:            WCD-22936 – 65-67 Elanda_SWMP.docx
Revision:             B                                                                   10