Catchment Description

The Killarney Vale and Long Jetty catchments are located on the Central Coast of New South Wales and occupy a combined area of 8.8 km2. The catchments include the suburbs of Bateau Bay, Shelley Beach, Long Jetty, Killarney Vale and sections of The Entrance. As shown in Figure 1, the catchments drain into Tuggerah Lake which forms the western boundary of the study area. Saltwater Creek is the major watercourse within the study area, with the remaining areas drained by constructed drainage canals and a sub-surface stormwater system. The catchments are largely urbanised with small sections of bushland and parklands.

Purpose of Study

During periods of heavy rainfall across the Killarney Vale and Long Jetty catchments, there is potential for water to overwhelm the stormwater drainage system and/or overtop the banks of the creeks and drainage canals and inundate adjoining properties. Flooding has been experienced across both catchments on a number of occasions in the past including 1981 as well as more recently in 2007 and 2010.

A number of flooding investigations have previously been completed in an effort to understand flood behaviour across different sections of the Killarney Vale and Long Jetty catchments and reduce the impact of flooding on the community. However, a comprehensive flood study of the entire catchments using modern computer models for a full range of design floods has not previously been prepared.

In recognition of this limitation and the damage and inconvenience that has been caused by past flooding across both catchments, Wyong Shire Council decided to prepare a Floodplain Risk Management Plan for the Killarney Vale and Long Jetty catchments. The first stage in the development of a Floodplain Risk Management Plan involves the preparation of a Flood Study. The Flood Study provides a technical assessment of flood behaviour.

This report forms the Overland Flood Study for the Killarney Vale and Long Jetty catchments. It documents flood behaviour across the catchment for a range of design floods for existing topographic and development conditions. This includes information on flood discharges, levels, depths and flow velocities for a range of design floods. It also provides estimates of the variation in flood hazard and hydraulic categories across the catchment and provides an assessment of the potential impacts of climate change on existing flood behaviour.