Smp

TABLE 3.1:WBNM SUB-CATCHMENT FRACTION IMPERVIOUS VALUES – EXISTING SCENARIO

 WBNM Sub-Catchment                            Area (ha)                                      Impervious (%)

 SUBA                                          1.43                                           50

 SUBB                                          4.29                                           10

 Total                                         5.71


The catchment lag parameter adopted was 1.6, which is within the accepted range of values provided in the WBNM technical reference
manual. Rainfall loss rates adopted are consistent with those from the Noosa River Flood Study (2017) and are an initial and continuing loss
of 15 mm and 2.5 mm/h for pervious surfaces respectively, and 0 mm and 0 mm for impervious surfaces. Modelling has been completed for
a range of standard design storm events ranging from the 63.2% AEP to the 1% AEP event, with durations ranging from 10 minutes to 3
hours. Peak flows tabulated in this report represent the peak values extracted from this range of storm events.

TABLE 3.2: EXISTING SCENARIO PEAK FLOWS

                             63% AEP         50% AEP          20% AEP         10% AEP         5% AEP           2% AEP          1% AEP

 WBNM (m3/s)                 0.60            0.72             1.11            1.41            1.68             1.99            2.23


  3.1.2       Developed Scenario (unmitigated)
For the Developed Scenario (unmitigated) the approved development was represented along with the new townhouse area proposed in the
south-west corner of the development. The development was represented within the WBNM model by adjusting the site sub-catchments
and the fractions impervious values. The catchment parameters applied in the Developed Scenario are provided in Table 3.4, with the
approved development represented as low density residential (50% imp), townhouse site (90% imp) and park area (0% imp).

The Developed Scenario catchment plan is shown in Figure 2.2

TABLE 3.3: WBNM SUB-CATCHMENT FRACTION IMPERVIOUS VALUES – DEVELOPED SCENARIO

 WBNM Sub-Catchment                            Area (ha)                                      Impervious (%)

 SUBA                                          1.430                                          50

 SUBB                                          4.408                                          50.7

 SUBC                                          0.140                                          50

 Total                                         5.978                                          -




73 EUMUNDI - NOOSA ROAD, NOOSAVILLE I BBNE00529_0002_0001-REP-001-0                                                                      11