Reference Document - MCU24 0155 (As Published)

DCM BUILDING DESIGN

18 SHEARWATER STREET, PEREGIAN BEACH – STORMWATER MANAGEMENT PLAN
5         CONCL USIO NS AND RECOMMENDATIONS

Based on the findings of the Rational method analysis for the site there is a slight decrease in runoff
of less than 1 L/s between pre and post development as shown in Table 5 below therefore, there is no
significant change in pre and post development flows from the site.

Table 5: Pre-development vs Post-development Comparison
            ARI                Pre-development           Post-development             Comparison
                               Discharge (Q, L/s)        Discharge (Q, L/s)              (L/s)
                        1                     10.88                     10.84                       -0.04
                        2                     12.91                     12.86                       -0.05
                        5                     19.35                     19.28                       -0.07
                       10                     23.90                     23.81                       -0.09
                       20                     28.70                     28.60                       -0.10
                       50                     36.84                     36.71                       -0.13
                      100                     42.75                     42.59                       -0.16

To address item 15 from Noosa councils Request for Information, there is no need for collection or
detention of stormwater runoff for the proposed site for the purposes of mitigating post development
flow to predevelopment levels however, as discussed in chapter 4 of this report, sufficient collection of
stormwater runoff is required to meet councils’ specific performance outcomes.

Although the site falls under Level 0 roof water design standards per QUDM Section 7.13.10, it is
recommended to discharge roof runoff via a minimum 150mm diameter uPVC pipe to the existing
open drain located in the rear (eastern) buffer. The outlet should include a small plastic headwall (or
similar) and at least 0.3m² of 100mm D50 rock to prevent scour and ensure free drainage. This
solution is feasible only if existing drain levels are sufficient to allow connection and would meet the
Level 1 drainage design criteria outlined in QUDM Section 7.13.11.




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