1909-13367 SRA referral response approved docs

                        Figure 3 – 1D model layout (Image from NearMap 2019)

The critical points for this model have been considered to be links 59 and 41 (see figure 2). Link 59 has
been chosen as it represents a critical point upstream of the development. Link 41 was chosen as it will
be the downstream end of the model and therefore represent the downstream condition.


3.1.7 Det e rm in at io n of cr it i ca l st o r m d ur at ion

Initially storm durations 30 minutes to 24 hours for the 50% to 1% AEP were run in the 1D model with
both runoff and hydraulic modes active with the 2D inactive. Later the 1 in 500, 1 in 2000 and PMP
events were run as a method of checking the model sensitivity.

The ensemble statistics utility within XPStorm was used to find the median storm at each of the above
selected critical links. The median storm was chosen in accordance with ARR 2016 guidelines. Table
2 shows the peak flows and critical storm for each of the design events at the above mentioned critical
locations.

The critical storms shown in table 2 range from 3 hours to 45 minutes.




                                                Flood Study                                           12
S19-007                                  122 & 144 Myall St, Cooroy