Author(s): Nicholas V. M. Odd; William Roberts; John Maddocks
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Abstract: There are a number of lagoons on the New South Wales coastline that have an entrance to the ocean, which are usually blocked by a sand barrier. The barriers build up over time and can reach a height of 2-3m above mean sea level. The water levels within a lagoon rise rapidly during occasional intense rain storms on the catchment until the water breaks out into the sea. This process is often helped by digging a trench across the top of the beach, to aid opening to reduce flood risk to properties upstream. Flood protection engineers need to be able to predict the time taken to reach the maximum rate of flow out of the lagoon and its magnitude. The paper describes the application and calibration of a modified version of TELEMAC, a 2D finite element system development by Laboratoire National d’Hydraulique, Chatou, France (Hervouet J M 1991), to simulate a breakout from the 50 hectare Wamberal Lagoon initiated and monitored by staff of NSW Public Works (1993) on 13 September 1993, when the lagoon was full but there was no rainfall.
Year: 1995