Killarney Vale and Long Jetty catchment flooding study released

An example of a blockage control structure with debris accumulation bay

A draft study exploring ways to minimise the impact of flooding in the Killarney Vale and Long Jetty catchment areas has been released by Central Coast Council for public comment.

The aim of this study and plan is to reduce the impact of overland flooding and flood liability across Killarney Vale, Bateau Bay, Shelly Beach, Long Jetty and The Entrance, within the Killarney Vale and Long Jetty catchments.

Each of the catchments is drained by a network of channels, stormwater drains and detention basins, and during heavy rainfall, overland or flash flooding can occur, which then flows into Tuggerah Lake.

The Killarney Vale/Long Jetty study only covers overland flooding from the local catchments draining into Tuggerah Lake.

Inundation from elevated water levels in Tuggerah Lake is not assessed as part of this study as this has been addressed in the Tuggerah Lakes Floodplain Risk Management Study and Plan.

The Killarney Vale/Long Jetty study takes in social, economic, environmental and flood risks and evaluates a range of potential mitigation measures.

Trouble spots identified in this study of January 2020, include: Hume Bvde and Wyong Rd near Macarthur St; Davidson Ave at Ferndale St; and, Wyong Rd near Kathleen White Cres, all at Killarney Vale.

Grandview St, Shelly Beach and Long Jetty sites at Elsiemer St, and The Entrance Rd at Norfolk St, are also problem areas.

Options for flood modification provided in the study aim to reduce the extent, depth and velocity of floodwater by upgrading drainage, detention basins, roadworks and earthworks.

They include recommendations for stormwater upgrades near Hume Bvde at Killarney Vale, with an estimated cost of $770,000; near The Entrance Reef Resort Motel, $1.6M; and near Kathleen White Cres, $530,000.

Roadworks and regrading flood modification options are: installation of kerb and gutter along Elseimer St and Pacific St, Long Jetty, $170,000; median modification near Wyong Rd culverts, $990,000; and, The Entrance Reef Resort, $150,000.

When cost estimates were prepared, the study also predicted reduction in flood damage costs if each option was implemented, along with the associated benefit-cost ratio.

The study recommended more detailed analysis of debris control structures upstream of Wyong Rd culverts, with two locations identified, under Wyong Rd near Kathleen White Cres and under Hume Bved near Macarthur St, estimated to cost about $120,000 over a 50-year period, assuming each track rack would be replaced after 25 years and maintenance every three months.

Other recommendations included updating local flood plans, community education and flood awareness, making flood data available to property owners, and advocate for fair and affordable property insurance premiums.

The report said, in general, that the options in the study could be implemented progressively over a five-year timeframe, yet, it was more likely to be a 10-year period because of the high capital cost and dependent on the budgetary commitments of Council and availability of funding from other sources.

To view the Killarney Vale and Long Jetty Catchments Floodplain Risk Management Strategy and Plan online go to yourvoiceourcoast.

Council is inviting submissions until 5pm on Wednesday, August 5.

Central Coast Council website
Reporter: Sue Murray