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.阿沃卡泻湖（Avoca Lagoon）是戈斯福德（Gosford）市内四座沿海泻湖中规模最大的一处。该泻湖呈十字形，表面积达97.5公顷，平均水深1.3米，泄放水位较平均海平面高出约2米。由于海岸动力过程的作用，泻湖入口通常处于封闭状态：海岸动力会在泻湖入口处形成一道海滩沙坝（beach berm），将阿沃卡海滩与北阿沃卡海滩连接起来。 戈斯福德市议会自1972年起便留存有阿沃卡泻湖入口开启的相关记录。这些记录显示，1976年至2003年间，泻湖入口共计被人工开启58次，主要用于防洪目的。另有4次自然开闸事件：当洪水导致泻湖水位上涨至海滩沙坝高度以上时，入口便会自然溃开。 关于海洋风暴侵袭阿沃卡泻湖的淹没记录，并不如入口开启记录那般完整。现有仅存1974年5月、1978年6月及1986年8月三次强海洋风暴的相关数据，彼时海浪翻越海滩沙坝并涌入泻湖。 洪泛区管理工作旨在推动采用一体化方案，对阿沃卡泻湖集水区内的所有土地实施管理。本次洪泛区管理研究涵盖以下议题： * 现有洪泛行为特征 * 环境与规划考量因素 * 未来发展规划 * 气候变化 * 洪灾损失情况 * 洪泛区管理可选方案 * 洪泛区管理实施影响 * 洪泛区管理经济分析 * 推荐洪泛区管理策略