Stormwater Management Plan - Rev 1

                                                                               20169 - SBSMP/1
                                                                                           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 – Roads, 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 Noosa Council’s Planning Scheme 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)

                                        11.3                   5.6


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 101-105 Eumundi Noosa Road, Noosaville