Study on sediment erosion during typhoon

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Study on sediment erosion during typhoon


Author: Tsang, Yip-ming
Title: Study on sediment erosion during typhoon
Degree: M.Sc.
Year: 2000
Subject: Ocean bottom -- China -- Hong Kong
Marine sediments -- China -- Hong Kong
Sediment transport -- China -- Hong Kong
Sedimentation and deposition -- China -- Hong Kong
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Civil and Structural Engineering
Pages: v, 65, [28] leaves : col. ill., col. maps ; 30 cm
Language: English
InnoPac Record:
Abstract: In this study, erosion of sea bed sediment during typhoon is investigated. A typhoon will generate winds and its energy will transfer to surface waves and then to the bottom of sea. Therefore, in this study, a wind model, a windsea model and a combined wave current bottom boundary layer model are adopted and combined to form a system of numerical models to investigate the sea bed sediment erosion due to Typhoon Sibyl in 1995. The bed shear stress associated with Typhoon Sibyl is estimated to be large enough to erode the consolidated layer of the sea bed. The actual erosion depth not only depends on the bed shear stress due to typhoon but also the bed material characteristics and the bed erosion history. Three cases are investigated to demonstrate the erosion pattern during typhoon. In the first case (Case 1), the sea bed is assumed to be consolidated in a calm sea for years. The second situation (Case 2) assumes that the sea bed consists of an infinite thickness of sediment with no consolidation or only lightly consolidation. In the third case (Case 3), the sea bed consists of two layers- the top layer with no or little consolidation and a deeper layer with one year's consolidation. Erosion during a typhoon is assumed to be a combination of these three cases or similar. Erosion depth would be about 1.58 m at hour 54 if the sea bed is composed of 1m of sediment having critical shear stress of 0.3 N/m2 at the top and sediment of critical shear stress of 1.85 N/m2 at greater depth. This reflects a typical order of erosion depth of the sea bed defined in Case 3 at the mouth of PRE due to Typhoon Sibyl. In addition, the erosion is also predicted to be more intensive at the mouth of PRE than the inner part of the estuary.

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