Attachment D - Stormwater Report · MCU18/0013

      Model Setup

      Two models were developed for the site. These are summarised as follows:

      Pre-developed model
                The existing site was modelled as a single catchment (Node A). The hydrograph of the catchment
                 was linked to and evenly distributed across a rainfall/ flow area grid at the rear of the site. The peak
                 flow rate discharging to Sunshine Beach was measured at a flow line at the rear of the site and the
                 total runoff volume discharging to Sunshine Beach was measured as the total runoff inflow at Node
                 A.

      Post-Developed Model
                The developed site was modelled as two catchments. The rear portion of the site consisting of
                 pervious areas (Node A) was modelled as per Node A for the pre developed model. The upper
                 portion of the site consisting of impervious areas was linked to a storage node (Node B) linked to the
                 2D network. This node was used to model the detention/infiltration tank. The peak flow rate
                 discharging to Sunshine Beach was measured at a flow line at the rear of the site and the total runoff
                 volume discharging to Sunshine Beach was measured as the sum of the total runoff inflow at Node A
                 and the total runoff outflow at Node B.

      The catchment data for each model is summarised in Table 2 below:

     Table 2 - Catchment Summary

      Model                    Node        Area (Ha)                   Slope (%)               % Impervious

      Pre Developed            A           0.0635                      25                      0

      Post Developed           A           0.0215                      25                      0

                               B           0.0420                      25                      100


       3.4             XP Storm Results
      The results of the ensemble statistics utility are presented in Figure 2 & Figure 3 below.




                               Figure 2 - Ensemble Statistics Utility Results; 10 year ARI

                                          24 Arakoon Street, Sunshine Beach QLD 4567
Job No – S18-003                             STORMWATER MANAGEMENT REPORT                                             4