The Floodplain Management Plan divides the Cockrone Lagoon area into six precincts: Cockrone Lagoon - Beach Berm High Hazard Floodway/Investigation Cockrone Lagoon - Entrance Area High Hazard – Low Hazard Floodway/Investigation Cockrone Lagoon - Storage Area Low Hazard Flood storage Cockrone Lagoon - Floodway Area High Hazard Floodway Merchants Creek - Floodway Area High Hazard Floodway Newell Road Floodway High Hazard Floodway These precincts have been classified for flood hazard as: High Hazard - Floodways - Cockrone Lagoon beach berm; - Cockrone Gully, from the upstream study boundary to its confluence with Cockrone Lagoon (identified as Cockrone Lagoon floodway); - Merchants Creek floodway from the confluence of Merchants Creek with Cockrone Lagoon to the upstream study extent; and - an existing open drain through the residential areas bounded by Newell Road and Three Points Avenue. High Hazard – Low Hazard Floodway (Floodway Investigation area) - Cockrone Lagoon at its entrance to the ocean (Floodway/Investigation Area); Low Hazard - Flood Storage - Cockrone Lagoon and foreshores excepting high hazard areas above. These precincts are illustrated on Figures 2 and 3, while Figure 4 provides greater detail in the Cockrone Lagoon Entrance Area. Council has adopted a policy of opening the lagoons when water level reaches RL 2.53 m AHD (identified as the let-out-level). Council has, in the past, also adopted a policy that requires new buildings to have floor levels above RL 4.3 m AHD. These two policies effectively constitute Council's current floodplain management practice around Cockrone Lagoon.

This Flood Study comprised the following principal stages: collection and assessment of available data; investigation of coastal processes to determine design ocean levels for tailwater boundary conditions for the hydraulic model and to determine ocean storm inflows into the lagoon; development and calibration of an hydrologic model to convert design storm rainfalls into design flood hydrographs; and development and calibration of an hydraulic model to determine design flood levels in the lagoon and on the floodplain. Available data comprises: Council records of lagoon openings (the most comprehensive available); Department of Land and Water Conservation (DLWC) Rainfall data at Kincumber Sewage Treatment Plant; and Bureau of Meteorology Daily Rainfall Records. The initial flood studies, outlined in this report, indicated significant sections of the Three Points Avenue area of MacMasters Beach would be flood liable. Ground survey of individual properties showed that the established model was not sufficiently refine to accurately represent the separate flow paths. An individual flood study was undertaken of the drain running parallel to Newell Road and Three Points Avenue. The study report appears as Addendum A to this document, while the results have been included on Figure 10.

Coastal Lagoon Catchments Overland Flood Study Final Report inc. appendices and figures

The main objective of this study (in two parts) has been to determine water levels in Brisbane Water for the full range of flood and ocean events that can occur due to the various natural physical processes, taking joint occurrence issues into account to some extent. The flooding behaviour can be influenced, either separately, or by a combination of, catchment rainfall runoff flooding, rainfall directly onto Brisbane Water, elevated ocean levels, local winds and, to a minor extent, the condition of the ocean entrance channel near Ettalong. The outcomes from this study include: -,

Complete report

This report documents the Burrill Lake Catchment Flood Study which defines existing flood behaviour and establishes the basis for floodplain management activities in the future.

Floodplain Risk Management Study and Plan June 2017

The Ourimbah Creek Floodplain Risk Management Plan has been prepared for the Central Coast Council in accordance with the NSW Government’s Floodplain Development Manual 2005 (Reference 1) and:  Is based on a comprehensive and detailed evaluation of factors that affect and are affected by the use of flood prone land;  Represents the considered opinion of the local community on how to best manage its flood risk and its flood prone land; and  Provides a long-term path for the future development of the community. The Ourimbah Creek catchment is located on the Central Coast of NSW, approximately 90km north of Sydney. Covering a total area of 160 km2, the majority of the catchment is contained in the Wyong Shire Local Government Area (LGA), with 8 km² of the catchment contained in the Gosford City LGA to the south. In 2016 the two councils were combined into the Central Coast Council. Flooding has been recorded periodically since the 1930’s but there are many more recorded instances of flooding in Tuggerah Lakes. It is possible that the incidence of flooding has historically been under reported along Ourimbah Creek and its tributaries. In recent times there have been two significant events, in February 1990 and June 2007. In both these events there was extensive flooding in the Newcastle, Lake Macquarie and Wyong/Gosford regions. Flooding causes significant hardship, including both tangible and intangible damages, to the community and for this reason the Central Coast Council has undertaken a program of studies to address the management of the flood problem in accordance with the NSW Government’s Floodplain Development Manual 2005 (Reference 1).

Complete report

Copy of full Floodplain Risk Management Study and Plan Report and appendices