Seabed erosion in an estuary during the passage of a typhoon

Y.M. Tsang, Wing Hong Onyx Wai

Research output: Journal article publicationJournal articleAcademic researchpeer-review

Abstract

This paper presents an estimation of the amount of sediments eroded in the Pearl River estuary (PRE) during the passage of Typhoon Sibyl in 1995. The estimation method depends upon a set of models applied in the following sequence: (1) a wind model for calculating the wind field; (2) the JONSWAP spectrum model for calculating the wave characteristics; (3) a multi-layer flow model (WAI et al, 1998) for calculating the tidal current; (4) a combined wave and current boundary layer model (GRANT and MADSEN, 1979) for calculating the bottom shear stress; and finally (5) a erosion model based on excessive shear stress concept for calculating the erosion depth. The seabed erosion estimation began when the center of Typhoon Sibyl was 720 km south-southeasterly away from PRE. Sibyl was closet to PRE, 280 km southwest from PRE, at hour 51 of the estimation. At this hour, the wind speed and wave height measured at Waglan Island, south of PRE, were 25 m/s and 2.3 m, respectively. Because the depth of seabed erosion is not only a function of apparent bed shear stress but also function of bed material characteristics and sediment consolidation history, different critical shear stresses were used in various layers of the seabed for the erosion estimation. The maximum bed shear stress computed by the present method during the passage of Typhoon Sibyl in the western sea boundary of PRE is about 4 N/m2 and the corresponding depth of erosion is 48 cm. It was found that although the water depth in the upper part of PRE was only a few meters, the erosion was evidently smaller than the one at the sea boundary of the estuary having water depth over 10 m. This indicates that the upper estuary was better protected from the attack of Typhoon Sibyl.
Original languageEnglish
Pages (from-to)370-381
Number of pages12
JournalJournal of Coastal Research
Issue numberSpecial Issue 34
Publication statusPublished - 2001

Keywords

  • Pearl River estuary
  • Hong Kong
  • Sediment transport
  • Bed shear stress
  • Combined waves and current.

ASJC Scopus subject areas

  • Earth-Surface Processes
  • Ecology
  • Water Science and Technology

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