Swmp

      2. STORMWATER QUANTITY
      The objective of this component of the study is to investigate the potential impact that the
      proposed development will have on peak flows discharging downstream from the site.

             Hydrologic Assessment
      Hydrologic modelling of the catchments has been undertaken using WBNM software (Boyd
      et al, 2019), developed jointly by the University of Wollongong, Rienco Consulting and
      Balance R&D. The 2012 version has been used for this investigation which utilizes ARR87
      hydrology.
      Modelling has been carried out for the 1, 2, 5, 10, 20, 50 and 100-year Average Recurrence
      Interval (ARI) storm events for the following scenarios:
          1. Existing Scenario (base case)
          2. Developed Scenario
          3. Mitigated Scenario

      2.1.1. Existing Scenario

      Sub-catchments have been delineated using 1m contours sourced from the NSC catalogue,
      developed using 2015 LiDAR and site survey. The fraction impervious values have been
      calculated using aerial imagery. Figure 2-1 shows the existing catchment delineation with a
      summary of parameters shown in Table 2-1.




      Figure 2-1: Existing Catchment Delineation




21-0166SMP01-V1 | Stormwater Management Plan | 25 Pavilion Street, Pomona                            |4