Attachment 4a - Engineering Report Part 1 · MCU18/0015

7.0    STORMWATER MANAGEMENT



7.1    Legal Point of Discharge


This existing overland flow path is considered to represent the legal point of discharge for
the proposed development (1.80Ha). Minor external catchments to the west (3.51Ha) will
be accepted onsite and conveyed to the existing flow path. The major external catchment
to the south and east (25.13Ha) will freely discharge onto the site from the eastern
boundary.



7.1   Flooding


A copy of Council’s Flood Map is included as Appendix D. The attached flood map indicates
that the site is free from inundation by the current 1% AEP flood event. It is noted that
minor flooding downstream of the site, within Noosa Parade, is due to tidal prisms within
Weyba Creek, which has direct connection to Laguna Bay to the north.



7.2    Stormwater Quantity Management


The site will be subject to limited development works and is expected to contain ≤ 20%
total impervious area in the post developed case (an increase from 3-5%) which will result
in a slight increase to peak discharge within the flow path which traverses the site.


The original design proposal included a detention volume within rainwater harvesting
tanks, provided for each new townhouse and detached dwelling. The revised proposal
provides an assessment of the existing drainage conditions on site and includes details of
external catchment runoff discharging through the site. Based on this assessment, it has
been determined that no onsite detention of stormwater runoff is required. Refer to the
following sections for details.


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