SCG 31030 Stormwater Management Plan · OPW22/0319

6.1.1    Design Storms:

Stormwater Drainage of the NSC Planning Scheme Policy outlines the following design storms.

            1.       Minor Drainage System                      10% AEP (ARI 10 years)
            2.       Major Drainage                              1% AEP (ARI) 100 years)

6.1.2    Rainfall Intensity:

Rainfall intensities were obtained from ARR for the Noosa region.

            I10            -          221 mm/h      (te = 5 min)
            I100           -          320 mm/h      (te = 5 min)

6.1.3    Time of Concentration:

Times of Concentration (Tc) were calculated as defined in QUDM –

                                                Table 6.1 – Tc Values

                                  Existing (Tc) (mins)         Post Development (Tc) (mins)
                                                                           5.0

6.1.4    Runoff Coefficient (C10):

The 10 year runoff coefficients (C10) were obtained for the development and determined as defined in QUDM.



                                               Table 6.2 – C10 Values

                                        Condition                         C10
                               Existing Site                              0.7
                               Post-development                           0.9


6.1.5    Fractions Impervious:

The following values were calculated for the impervious areas: -

                          Site Area                 -         1510m2
                          Impervious Area           -          300m2 (pre-development)
                                                    -         1316m2 (post development)

6.1.6    Peak Flows:

Table 6.3 below displays a summary of major and minor discharge rates for pre and post development conditions.

                   Table 6.3 – Pre and Post Development Peak Flow Rates – Rational Method

                       Condition                        Q10 (m3/s)              Q100 (m3/s)
                    Pre-development                      0.093                   0.158
                    Post-development                     0.103                   0.169


6.2.1    Peak Flow Mitigation:

As shown in Table 6.3 Stormwater runoff will increase as a result of the proposed development using the Rational
Method. Therefore, it is proposed to utilise an on-site detention tank to mitigate the peak stormwater discharge
rates from the proposed development prior to discharging to the lawful point of discharge as discussed in section
4.2.




 SCG Consulting engineers                                      7                              SCG Ref: 31030(SWM)


[OCR of page images]
6.1.1 Design Storms:
Stormwater Drainage of the NSC Planning Scheme Policy outlines the following design storms.

1. Minor Drainage System 10% AEP (ARI 10 years)
2. Major Drainage 1% AEP (ARI) 100 years)

6.1.2 Rainfall Intensity:
Rainfall intensities were obtained from ARR for the Noosa region.

lio - 221 mm/h (te
loo - 320 mm/h (te

5 min)
5 min)

6.1.3 Time of Concentration:
Times of Concentration (Tc) were calculated as defined in QUDM —

Table 6.1 — T, Values

 

Existing (T.) (mins) Post Development (T.) (mins)
5.0

 

 

 

 

 

6.1.4 Runoff Coefficient (C10):

The 10 year runoff coefficients (C10) were obtained for the development and determined as defined in QUDM.

Table 6.2 — Cio Values

 

 

 

 

 

 

Condition Cro
Existing Site 0.7
Post-development 0.9

 

6.1.5 Fractions Impervious:
The following values were calculated for the impervious areas: -
Site Area - 1510m?2
Impervious Area - 300m? (pre-development)
1316m? (post development)
6.1.6 Peak Flows:

Table 6.3 below displays a summary of major and minor discharge rates for pre and post development conditions.

Table 6.3 — Pre and Post Development Peak Flow Rates — Rational Method

 

 

 

Condition Qio (m*/s) Qi00 (m/s)
Pre-development 0.093 0.158
Post-development 0.103 0.169

 

 

 

 

 

 

 

6.2.1 Peak Flow Mitigation:

As shown in Table 6.3 Stormwater runoff will increase as a result of the proposed development using the Rational
Method. Therefore, it is proposed to utilise an on-site detention tank to mitigate the peak stormwater discharge
rates from the proposed development prior to discharging to the lawful point of discharge as discussed in section
4.2.

SCG Consulting engineers 7 SCG Ref: 31030(SWM)