Typhoons driven morphodynamics of the Wan-Tzu-Liao sand barrier (Taïwan)

Campmas Lucie, Bouchette Frédéric, Meulé Samuel, Petitjean Lise, Sous Damien, Liou Jiing-Yih, Leroux Mallouf Romain, Sabatier Francois, Hwung Hweng Hwung

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

This study focuses on the dynamics of the Wan-Tzu-Liao sand barrier when it is struck by one typhoon, a group of typhoons or the whole season of typhoons and monsoon. In the framework of the KUN-SHEN project, 7 months of monitoring (2011-2012) provided 20 topobathymetric surveys (within a 200 m long segment of the barrier from the subtidal zone to the back-barrier) and acquisitions of offshore, nearshore and shallow water hydrodynamics including velocity profiling, free surface measurement and absolute pressure. Offshore waves were extracted at Cigu buoy (18 m of water depth). Nearshore waves were acquired from the current profiler deployed 400 m off the coast in 4 m of water depth and water level on the subaerial beach were acquired from two pressure sensors deployed in the lower part of the subtidal zone and the dune crest. Morphologic changes of the emerged beach were monitored using D-GPS each week during winter monsoon season and just before and after each event during summer typhoons season. Amongst the eight studied typhoons, TALIM is the most energetic event observed. Offshore wave height reached Hs = 10.34 m (Tp = 14.6 s) at Cigu buoy and Hs = 2.3 m (Tp = 13.4 s) at the profiler. Surface waves dynamics throughout surf and swash zones are progressively dominated by infragravity motions. A part of the dune is surged at the storm apex. Morphological changes include 6.7 m of dunefoot retreat and a sand transfer from a dune breach to wash-over deposits in the lagoon. More surprisingly, the foreshore was nourished (2261 m3 +/- 268 m3) as well as the whole sand barrier (+1920 m3 +/- 1071 m3). The sand input is concomitant to the redistribution of sand from the intertidal sandbars interpreted as the ultimate stage of the subtidal bars landward migration. Although winter are erosive season (-4995 m3 +/- 1071 m3), the summer results in an accretion period (3556 m3 +/-1071 m3) with a shoreline seaward shift about 10.4 m. Over the annual time period, the sand barrier recorded 18.4 m of retreat coupled with a small sand loss (-1439 m3 +/- 1071 m3) without any significant abrasion of the dune-top.

Original languageEnglish
Title of host publicationProceedings of the 34th International Conference on Coastal Engineering, ICCE 2014
EditorsPatrick Lynett
PublisherAmerican Society of Civil Engineers (ASCE)
ISBN (Electronic)9780989661126
Publication statusPublished - 2014
Event34th International Conference on Coastal Engineering, ICCE 2014 - Seoul, Korea, Republic of
Duration: 2014 Jun 152014 Jun 20

Publication series

NameProceedings of the Coastal Engineering Conference
Volume2014-January
ISSN (Print)0161-3782

Other

Other34th International Conference on Coastal Engineering, ICCE 2014
CountryKorea, Republic of
CitySeoul
Period14-06-1514-06-20

All Science Journal Classification (ASJC) codes

  • Civil and Structural Engineering
  • Ocean Engineering
  • Oceanography

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