Attachment C - Stormwater Management Plan - 30-32 Doonella Street_SMP-revA_full (00016826)

aquaintel

3.3. Developed Scenario

The proposed development has been incorporated into the WBNM model by
adjusting the fractions impervious values, with the catchment area remaining
unchanged. Fraction impervious values of the existing and proposed scenarios are
provided in Table 11 below.

Table 11: WBNM Sub-Catchment Fraction Impervious Values — Developed Scenario

 

 

Area (ha) Developed Scenario Existing Scenario
Impervious (%) Impervious (%)
0.2527 75 20

 

 

 

 

 

Peak flows tabulated in this report represent the peak values extracted from the
modelled range of storm events.

Table 12: Developed Scenario WBNM Outlet Peak Flows

 

 

 

 

 

 

 

 

Existing Peak Flow Developed Peak Flow Change in Peak Flow

(m?/s) (m/s) (m?/s)

1 year 0.08 0.08 0.006
2 year 0.10 0.10 0.007
5 year 0.12 0.13 0.006
10 year 0.14 0.14 0.007
20 year 0.16 0.16 0.006
50 year 0.16 0.18 0.014
100 year 0.18 0.19 0.014

 

 

 

 

 

 

It can be seen that the peak flows have increased to the catchment outlet. This is a
result of the development site increasing the impervious area. Mitigation within the
catchment will be required in the form of a detention tank.

11