2021-07-06 Planning & Environment Committee Meeting Agenda

PLANNING & ENVIRONMENT COMMITTEE MEETING AGENDA                                          6 JULY 2021


The application was forwarded to an external Environmental and Civil Engineering consultant for
comment, who provided the following comments specific to the fill proposed on the site:
I don’t believe the proposed filling will have any measurable impact on flooding.
It can be seen from the below extract from Council’s 1%AEP flood mapping that the flooding
affecting the site is backwater flooding due to the flow restriction at Church Street. In other words,
the flooding can be described as very low velocity pooling of water back into the gully adjacent to
the site.
Filling can potentially impact flood levels through either restricting the available flowpath (reduction
in flood conveyance) and/or displacing floodwater through a reduction in flood storage. In this
situation, due to the low velocity backwater nature of the flooding, the only mechanism that is
relevant is potential reduction in flood storage.
As the reduction in flood storage caused by the filling is very small relative to the total storage
available at this location, the impacts would be expected to be negligible.
The area of filling which is triggering the application (more than 3m from main building) is generally
the fill batter (apart from the patio). The 1%AEP flood level at 2100 is 91.8mAHD, which
corresponds to an area of filling of approximately 30m2 which is both outside of the 3m building
setback and subject to fill. The total inundation area for this gully during this event is ~3,000m2.




                                Figure X: Council’s 1%AEP flood mapping

Council’s Environment Officer also reviewed the proposal plans and did not raise any concerns
regarding the fill and proximity to waterway.
The proposal complies with PO21, as the fill will not cause ponding of water on the site or nearby
land, will not increase flooding and will not affect the flow of water in any overland flow path. In
addition, the fill is proposed to create a flat house pad and outdoor recreation area only, and is
located in proximity to the existing shared access driveway for 11A and 11B Church Street only,
and as such will not adversely affect the privacy or visual amenity of surrounding property. In this
regard, it is recommended that the application be supported.

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