A review of floodwater heights in Coffs Harbour has revealed how much water is being held back from the CBD by the city's flood detention basins.
A review of floodwater heights in Coffs Harbour has revealed how much water is being held back from the CBD by the city's flood detention basins. Contributed

Basins are holding back a deluge of floodwater

A REVISED flood study for the Coffs Creek catchment that uses the most recent rainfall data and computer modelling will be out for public comment from February 28 until March 30.

"The draft Coffs Creek and Park Beach Flood Study project provides a revised flood model for Coffs Creek and an assessment of possible future floodplain management options for drainage in the Park Beach area," the council's Section Leader for Local Planning Sharon Smith said.

The study also highlights estimated levels and observed flood levels from 1996 and 2009 and includes the impact made by the four flood detention basins that the council has built since the 2009 floods.

The new flood model shows the detention basins are typically dropping flood levels by 200mm-600mm in sections of the mid to upper reaches of Coffs Creek and 200mm-400mm around the Coffs CBD.

However, the improved rainfall data, terrain data and 2D computer modelling does also identify some areas where flood level estimates have increased compared to previous studies.

The study contains mapping of flood extents, levels, depths, and velocities for the 1 in 20, 50, 100, 200 and 500 year flood events, as well as the PMF (Probable Maximum Flood) event.

The study recommends that the council proceed to a review of options for the whole of the Coffs Creek catchment " resulting in the preparation and review of the council's existing Floodplain Risk Management Plan."

It also looks at drainage modifications for reducing flood risk within Park Beach.

"The Park Beach area acts like a basin which fills and drains slowly," Ms Smith said.

"The study looks at these limitations and provides options including upgrading the pipe network leading to the outlet at Macauleys Headland, upgrading culverts beneath the railway line and upgrading other key drainage lines leading to various outlets.

"The outcomes of the study will be used to prioritise drainage improvement works in this area."

The council on Thursday night voted to place the draft study on exhibition for public comment from February 28 until March 30.

The draft study and details of how to make a submission can be viewed at the council's Customer Service Centre, local libraries and online at haveyoursay.coffsharbour.nsw.gov.au from Wednesday.

A report on the results of the public exhibition will be presented to the council at a future meeting.



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