Attachment 3 - Additional Information Barlow Shelley

Only detail for the subject site was included within the FHAR although modelling of the
entire catchment area and flow cross section was analysed. This was clearly conveyed
within the report, as noted above, and the additional full width cross section in Figure A
above shows that approximately 30% of the flow passes through the site west of the
new residence and the remaining 70% bypasses the site within the Noosa National Park
east of the new residence.


Item 2
The modelling makes no allowance for fence blockages and appears to be too
localised to provide meaningful results. While I have not inspected the site, aerial
imagery shows that a tennis court is situated immediately downstream. Given the
bushland catchment, there is a high potential for a chain wire fence to become
highly blocked with debris and this will increase flood levels through the site.

We acknowledge that the report only addresses the subject site and is not intended to
be a model of the full extent of flow path upstream and downstream of the site. From
Council’s Information Request dated 8 May 2018, information was only required to
demonstrate that the proposed drainage easement was of sufficient width/area to
encompass the 1% AEP stormwater flows. The submitted FHAR addresses this matter.

Furthermore, Section 7.2.2 of the report states – “It was found that the existing
residence is provided at least 580mm freeboard from the current calculated peak water
surface level (14.220m AHD), being 280mm higher than the required 300mm freeboard
in accordance with the latest Noosa Plan”.

Any local increases in flow depth due to debris build-up against the downstream tennis
court fence will not be significant enough to affect the existing residence as the floor
level is approx. 800mm above the 1% AEP at the downstream face and 580mm above
at the upstream face which provides an adequate factor of safety and complies with
Council’s codes and policies.


Item 3
No comments have been provided in regards to the flood resilience of the
dwelling. It is situated within a natural bushland flow path and it will be subject to
flooding from time to time (certainly below floor level). It would need to be
demonstrated that the house is resilient to flooding and given consideration to
the high levels of natural debris that is likely to be mobilised during a large flood.

We confirm that Barlow Shelley Consulting Engineers were the structural engineers for
the new eastern portion of the residence which was a known fact to Council. The
opening paragraph in the FHAR dated June 2018 states – “Barlow Shelley Consulting
Engineers Pty Ltd has been commissioned to undertake a Flood Hazard Assessment
Report (FHAR) for the existing residence at 20 Mitti Street, Noosa Heads. This report
has been prepared as an addendum above and over the previous overland flow review
undertaken by Barlow Shelley Consulting Engineers dated 3 August 2016.”



1443-03 – Mitti Street, Noosa Heads                                                        3
TS/ts