H - Revised Integrated Water Management Plan by Cardno (inc MUSIC file) (13.09.19)

                                                                                   Integrated Water Management Plan
                                                                           Noosa Marketplace : 2-20 HOFMANN DRIVE



7.5             Severe Storm Impact Assessment
A severe storm impact scenario was prepared for the post development case. In this scenario all of the culverts
and pipes were modelled with 100% blockage, as per QUDM 2017 suggested values in Table 7.5.1. The 1%
and PMF AEP events were modelled in this scenario to ensure that the safety of persons on site is not
compromised and floor levels have sufficient free board. Hazard areas were assessed using the hazard curves
as shown in Figure 7-11.
To assess the PMF, the Generalised Short Duration Method was used which can calculate the greatest flood
depth for a given duration at a particular location. Using the method, the maximum flood depth was then
converted into a spatial distribution for use within the hydraulic model.
Mapping produced for the above events shows that the safety of people will be protected on site during these
events with no inundation of the carpark or building areas. Access to the site is only limited for approximately
24 minutes during the PMF at the main entrance. As the site has three exit points that can be utilised in case
of emergency this period of limited access is not considered significant. Blocking the drainage network had
minimal effect on the peak water surface levels during the 1% AEP event due to the existing network being
ineffective for events of this size. The site remains accessible during the 1% AEP.
At the access off Hofmann Drive roundabout hazard mapping for the PMF event shows that an exit route
remains available to Eenie Creek Drive for all but small vehicles. Water surface elevation recorded at Point 5,
(Figure 7-12) show a decrease in the peak water level at this location in the developed case (Figure 7-10).

                                    P5 PMF WSE
                13.9
                12.9
   WSE (mAHD)




                11.9
                10.9
                 9.9                                           Developed
                 8.9                                           Existing
                 7.9
                 6.9
       -0.3                0.2                0.7        1.2
                                 Time (hrs)


Figure 7-10        Point 5 Water Surface Elevation




Figure 7-11        ZAEM1 Flood Hazard Curves




V190428 | 10 September 2019 | Commercial in Confidence                                                          34