Avoca Lagoon Floodplain Management Study

Avoca Lagoon is the largest of the four coastal lagoons within Gosford. The lagoon has a cruciform shape\r\nwith a surface area of 97.5 hectares and average depth of 1.3 metres. The let-out-level is approximately 2\r\nmetres above mean sea level. The lagoon entrance is normally closed due to the action of coastal dynamic\r\nprocesses which result in the formation of a beach berm across the lagoon entrance, linking Avoca and\r\nNorth Avoca beaches.\r\nGosford City Council has records of openings of the Avoca Lagoon entrance commencing in 1972. These\r\nrecords show that the entrance has been opened 58 times over the period 1976 to 2003, primarily for flood\r\ncontrol purposes. The entrance has broken out naturally on four other occasions when floodwaters caused\r\nthe lagoon level to rise above the level of the beach berm.\r\nRecords of inundation of Avoca Lagoon by ocean storms are not as complete as those available for the\r\nopening of the entrance. Limited data are available for severe ocean storms in May 1974, June 1978 and\r\nAugust 1986 when waves overtopped the beach berm and entered the lagoon.\r\n\r\nThe floodplain management process seeks to promote the adoption of an integrated approach to the management of all lands within the Avoca Lagoon catchment.\r\nThis floodplain management study addresses the following issues:\r\n\r\n* existing flood behaviour;\r\n* environmental and planning considerations;\r\n* future development;\r\n* climatic change;\r\n* flood damages;\r\n* floodplain management options;\r\n* floodplain management impacts;\r\n* floodplain management economics;\r\n* preferred floodplain management strategies.