ATTCH 3 - IR Response - Erosion, Coastal Processes and Stormwater (Dr Trevor Johnson)

Kenlynn Pty Ltd Report Number 620.12166-R01

Castaways Beach 3 November 2017
Stormwater Management Plan Version v0.1
Page 5

 

runoff to manage frequent flows to not change to 1% AEP (sic) and achieve pollution reduction
targets of 80% reduction of Total Suspended Solids, 60% reduction of Total Phosphorous and
45% reduction of Total Nitrogen compared to a non-mitigated scenario. Additionally, Specific
Outcomes O01, O9 and O10 of the Water Sensitive Design Code of the Noosa Plan requires
developments to not adversely affect water quality, water flows or ecological values of the
receiving environment. For this development, further information is needed to confirm the
receiving environment will not be adversely impacted. The concerns with flow management are
to do with scour at the stormwater outlets, impact of scour on slope stability. Concerns with
changes to water quality have to do with potential for nutrient increases to Burgess Creek,
especially when it is closed as well as impacts of locally increased nutrients to dunal vegetation.

The application is unclear whether runoff from the development will discharge via groundwater
or overland flow to Burgess Creek or elsewhere. The size and location of any required
stormwater management devices that will result from the proposed subdivision and the impacts
it could have on site stability, asset management etc. may potentially affect lot layout/
easements etc.

Information Required

9. Demonstrate that the proposed development will meet the environmental objectives for
water quality management as required by the SPP and The Noosa Plan.

10. Provide a preliminary stormwater strategy which identifies the proposed stormwater outlet
locations and flow paths as a result of the proposed development.

11. Provide advice from a suitably experienced and qualified geotechnical engineer to
confirm that the proposed stormwater discharge strategy will not affect stability on
landslip areas or cause erosion.

This Stormwater Management Plan addresses Items 9 to 11 from the above Information Request.

SLR Consulting Australia Pty Ltd