BsmRevRpt2

4.0     RESPONSE TO SAUNDERS SUBMISSION

J R and F Saunders wrote to Noosa Council on 3 September 2014, requesting clarification of particular
aspects of the original edition of this report, and expressing concern about possible local stormwater
impacts on their property. The Saunders property is marked on Figure 9 of this revision of this report.

Their requests are reproduced in italics, below, with a response immediately following each request:

On page 15 of the study, there are three groups of columns, but they are not labelled with recurrence
intervals. Please confirm there are from left to right: 10 Year, 20 Year and 50 Year.

The three columns should indeed have been labelled 10 Year, 20 Year and 50 Year. The oversight has
been corrected in this revised report.

Using Figure 6, we understand the nearest model node to our property is Node 29. On page 15, assumed
Q10, Node 29, the afflux is 1.07 metres with a flood level of 100.957 metres. This afflux seems to be
incorrect because:

1. assumed Q20 has an afflux of 0.09 meters with a flood level of 100.033 meters

2. for assumed Q10, the flood level does not fall from Nodes 28 > 29 > 30

The quoted afflux was indeed incorrect, and resulted from the incorrect transcription of the post-
development flood level as 100.957, when it should have been transcribed as 99.957, which would have
resulted in afflux of 0.07 metres. Incidentally, the modelling has since been revised, with more detail in
this particular area of the model network, and the affluxes at node 29 are now less than zero.

… we are concerned about the potential for scouring in our property if there is not an appropriate energy
dissipation structure on the overland flow path located near our side fence and between proposed lots 39
and 40. We believe that this structure should be located within the development.

The peak-rates of local runoff across the boundary at this location will be substantially reduced, by
diversion of flow eastward within the development, and this will substantially lessen the likelihood of
scouring. Any other works that may be required to ensure that the velocity and concentration of the
remaining flows across the boundary are no worse than existing, will be part of the normal operational
works design for such a scenario.




      Brisbane Stormwater Management Pty Ltd Document File: ValkevSDF.Doc                              Page 8