AGENDA - Sunshine Coast Council

Strategy and Planning Committee Agenda 16 February 2011
CANAL AND LAKE SYSTEMS
The proposed layout includes an extension of the tidal canal off the Lamerough Canal and
the construction of an additional partial tidal lake which will in effect create an island within
the centre of the site. The extension of the tidal canal is proposed to include a marina basin
with a base level of -5m Australian Height Datum. The proposed lake has a surface area of
14.8 hectare and a depth of approximately 5m below the mean lake surface level under
current climatic conditions (-4.5 m Australian Height Datum).
The two water bodies will be linked by a navigation lock and weir located on the southern
arm of the loop. The northern arm of the loop will be blocked to the passage of watercraft
with the construction of a bunded causeway to allow the crossing of a road into the District
Business Centre. Lake flushing is proposed via a tidal exchange system which will be
controlled by actuated penstocks at the lock and under the bunded causeway. This system
will force one-way flow around the lake in a clockwise direction (refer Attachment 4).
The primary purpose of the lake, and reason why the lake is proposed to be approximately
5m deep, is to source fill so that the proposed development has adequate freeboard to
flooding both now and under future climate change conditions.
The proposed tidal exchange system does not involve any pumping of water from Bells
Creek or Pumicestone Passage and does not include any outlets to Bells Creek.
WATER QUALITY
Lake Water Quality
A new lake is proposed with a surface area of 14.8 ha in size and a depth of approximately
5m below the mean lake surface level under current climatic conditions (-4.5 m Australian
Height Datum). The primary purpose of the lake and reason why the lake is proposed to be
approximately 5m deep is to source fill so that the proposed development has adequate
freeboard to flooding both now and under future climate change conditions.
It is important to note that Acceptable Solution S35.1 states that an acceptable solution for a
canal, channel and small boat mooring facility is that it has a maximum depth of 6 m. The
proposal is therefore in accordance with this Acceptable Solution. The proposal is also in
accordance with the requirements of Section 11.6.3 of Council’s Development Design
Planning Scheme Policy which deals with design requirements for Canals.
The lake itself sits outside of any of the precincts so the conditions need to include a level of
detail appropriate to enable the applicant to go straight to lodging an application for
operational works for the lake, marina and lock and weir infrastructure.
There are two key strategies proposed for maintaining the quality of stormwater within the
proposed lake. Firstly a system is proposed to achieve turnover of the lake water with that of
Lamerough Canal. A lake turn over time of 22 days is proposed which is proposed to result in
an effective lake turnover time of 30 days. The 22 day lake turnover is required to achieve an
effective 30 day lake turnover because the modelling shows that there will be some short
circuiting around the marina basin. This means that rather than lake turnover occurring with
the entire Lamerough Canal a portion of the lake water is recirculated through the system.
Modelling has been performed showing that Lamerough Canal has a 4.5 day turnover with
the Pumicestone Passage.
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