Appendix B- SWMP

                                                                               23098 - SBSMP/2
                                                                                        Page 8




5 STORMWATER QUANTITY
A roof and allotment drainage system is to be designed to comply with:

    1. AS/NZS 3500.3:2015 - Plumbing and Drainage Part 3: Stormwater Drainage;

    2. The Queensland Urban Drainage Manual (QUDM), and;

    3. The Noosa Council Engineering Design Standards – Road, drainage and earthworks.


5.1 Rational Method Assessment
The Rational Method has been used to calculate the peak discharges from the site under the
existing (pre-development) and proposed (post-development) conditions.

5.1.1 Design Storms
As defined in the BRC Planning Scheme Policies the following design storms were adopted:

    1. Minor Drainage System: 10 year ARI statistical flood (Q10 storm);

    2. Major Drainage System: 100 year ARI statistical flood (Q100 storm).

5.1.2 Rainfall Intensity
Rainfall intensities for this study were obtained from the Australian Bureau of Meteorology.

5.1.3 Times of Concentration
Times of concentration (tc) were calculated as defined in the QUDM. Refer to Table 5-1 for the
adopted tc’s and Appendix E for tc calculations.

                                     Table 5-1 – Adopted tc values
                                   Pre development         Post development
                                       tc (mins)                tc (mins)

                                          10                     5.5



5.1.4 Runoff Coefficients
The 10 year runoff coefficient’s (C10) were determined as defined in the QUDM. Refer to Table 5-2
below for the adopted C10 values.

                                      Table 5-2 – Adopted C10 Values

                                         Property State                C10

                                       Pre-development                 0.75
                                       Post-development                0.85




Site Based Stormwater Management Plan
Proposed Townhouse Development at 5 Pearl Street, Cooroy