Stormwater Management Plan

SC5594 – Walter Hay Dr, Noosaville                                                             11




4.3      Modelling Overview
4.3.1    Methodology
The software package XP-STORM V2016, has been used to model the site in its current and post-
developed state. The modelling has been undertaken to determine detail design parameters of on-site
detention to replicate pre-development peak flow rates. As the development falls within the ‘Urban
Residential’ development category (QUDM Table 7.02.1), the minor (10yr ARI) and major (100yr ARI)
storm events were primarily sized for underground and overland design flows respectively.


All events ranging from 1, 2, 5, 10 20, 50 and up to the 100yr were analysed to compare pre/post
development discharges ensuring ‘non-worsening’ discharge. The development modelling and analysis
undertaken was based on the information provided by the detailed site survey and preliminary architectural
layouts. A rational method check of the pre-development scenario was conducted to calibrate the XP-
STORM model.


4.3.2    Catchment Areas
The subject site has been modelled in its existing pre-development and proposed post-development states
with the catchment areas illustrated in Tables 4.1 & 4.2 and Appendix A. In its pre-development state the
subject site was modelled as one hydrologic node to replicate the existing sheet flow situation for the lot.
XP-STORM model outputs are included in Appendix C of this report.


 Node                 Description                       % Impervious      Area (Ha)


 ‘PRE’                Landscape                         0                 0.890


 Total Catchment (ha)                                   0                 0.890
Table 4.1 - Pre Development Node Sub-Catchment Areas


 Node                        Description                % Impervious      Area (Ha)
 Combined                    Roof                       100               0.355
 Post-development            Carpark/hardstand areas    100               0.197
 Catchments                  Landscape                  0                 0.441
 Total Catchment (ha)                                   55                0.993
Table 4.2 - Post Development Sub–Catchment Areas