REPS - Technical Memorandum

applied to the sizing of all detention tanks.
c. A stormwater design calculation table.
d. Details of detention outlet orifices / controls.
f. Prepared by a suitably qualified person (RPEQ)

RECOR RESPONSE:

A 12d Model drainage analysis was conducted for the entire site. The 1% AEP (Q100) and 10% AEP
(Q10) hydraulic grade lines (HGLs) are presented in the stormwater long section plans for reference.

The site drainage and detention/ rainwater harvesting tanks have been modelled in 12d using the
ILSAX method of dynamic drainage analysis. All rainfall data was obtained from the Bureau of
Meteorology (BOM) Intensity-Frequency-Duration (IFD) data website and is based on the latest 2019
data. The rainfall data obtained was then multiplied by a factor of 1.2 to simulate an increase of 20%.
Refer tables 1 and 2 below for the original and climate change adjusted rainfall data.

Table 1: IFD Table


    Annual Exceedance Probability (AEP)

    Duration                              63.2%   50%#   20%*   10%      5%       2%       1%

    1 min                                 173     195    263    308      351      405      446

    2 min                                 147     167    230    273      316      375      420

    3 min                                 138     157    215    254      293      346      386

    4 min                                 131     149    203    239      275      321      357

    5 min                                 125     142    193    227      259      301      333

    10 min                                103     116    155    181      205      236      259

    15 min                                87.0    98.1   132    153      174      199      218

    20 min                                76.0    85.7   115    134      152      175      192

    25 min                                67.8    76.5   103    120      137      158      173

    30 min                                61.4    69.3   93.5   109      125      144      159

    45 min                                48.6    55.0   74.9   88.2     101      118      131

    1 hour                                40.8    46.3   63.5   75.2     86.5     102      113

    1.5 hour                              31.7    36.1   50.2   59.8     69.4     82.2     92.2

    2 hour                                26.5    30.3   42.4   50.8     59.2     70.6     79.5

    3 hour                                20.5    23.6   33.5   40.4     47.4     56.9     64.4

    4.5 hour                              16.0    18.4   26.5   32.2     37.9     45.8     52.0

    6 hour                                13.4    15.5   22.5   27.4     32.4     39.2     44.6




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