Coffs Creek dredging part of plan
INVESTIGATING commercial dredging of sand from the entrance to Coffs Creek is the sixth point of Coffs Harbour City Council’s nine-point flood mitigation plan.
The proposal is to investigate dredging an area of the lower estuary from about 200m downstream of the railway bridge to about 400m upstream of the Orlando Street Bridge.
Coffs Harbour City Council general manager Stephen Sawtell reported to councillors that dredging of the lower estuary provided only limited flood mitigation benefits.
This reach of the creek was considered in the 2005 Flood Study.
Mr Sawtell reported that modelling for the 2005 Flood Study showed the maximum flood reduction from such dredging in an estimated 1-in-100-year flood with elevated storm tide conditions was just 0.1m immediately upstream of the area to be dredged, with the benefit reducing upstream until by Grafton Street it was limited to 0.01m.
The modelling showed greater reductions might be evident under other flood conditions with normal tides.
Consequently he said dredging would be difficult to justify for flood mitigation alone, but might be justified for other purposes such as improved aesthetic qualities; recreational waterway activities, and the use of the sand in nourishing Park Beach.
Mr Sawtell reported that dredging to a depth of 1m below present sand levels would involve the removal of up to 40,000 cubic metres of sand that would cost about $600,000 at today’s rates.
In October, Coffs Harbour City Council dredged more than 4000 cubic metres of sand from Coffs Creek near the Pet Porpoise pool, which was used to nourish a small recreational beach near Park Beach Surf Club and this cost about $50,000. He said commercial dredging was another option.
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