06/0210 - Response to request for information darted 14/03/06 [As Published] · 132006.210

5. FLOOD BOUNDARIES
The flood boundaries that result from the predicted 100 year flood levels are marked on Figure 5.

The proposed building platform on the site is seen to be clear of the 100 year flood boundary. Note,

_ however, from Figure 5, that there will be some local surface runoff towards the building platform,

for which appropriate allowance should be made in the construction.

The only significant intrusion of flooding onto the site is at the south-west corner. This intrusion is
caused by the kerb overflows, not the main floodway. This corner could be filled, if required, to
make the site flood free; - this would involve only about 2 cubic metres of filling. This would raise
the 100 year flood level at cross-section 12 by 0.04 metre (to EL 105.76, as on page 12 of the
Appendix), while the flood levels at all other cross-sections would be unaffected.

The proposed access along the unformed part of Topaz Street, to the proposed new dwelling at the
rear of the existing house, will cross the kerb overflow path in two places; - at cross-section 14 and
between cross-sections 17 and 18. The kerb overflows will occur only once in 10 to 20 years, as on
page 9 of the Appendix, and then only for a few minutes at a time (because of the small catchment
area). In a 100 year storm, the velocity and depth at cross-section 14 will peak at 0.14 metres and
0.79 m/sec, leading to a DxV ratio of 0.11, which should be easily trafficable.

 

Brisbane Stormwater Management P/L Doc File Topaz.Rpt - 30 Oct 2006 Page 4