Recent changes of channel morphology in a coseismic uplift reach of the taan river in central Taiwan

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Abstract

The Taan River is located in central Taiwan. A reach about 1 km long in its middle stream, was uplifted up to 10 m during the Chi-Chi earthquake that occurred on 21 September 1999. The outcrop bedrock in this reach is Pliocene sedimentary rock formation, composed of sandstone, siltstone, mud-stone, and shale. From 1999 to 2010, the channel morphology of the uplift reach was incised and changed rapidly through four distinct stages. The four stages, in order, were (1) loss of armor layer (1999–2001), (2) intense incision of exposed bedrock (2001–2004), (3) formation of main channel (2004–2007), and (4) gradual return to the channel slope prior to the earthquake (2007–2010) (Huang et al., 2013). This study explores the recent morphological changes of the uplift reach via field observation and aerial-photo comparison. From 2010 to 2016, the bedrock erosion remained active. Instead of channel incision in the previous stages, the major process of the bedrock erosion in this reach has turned into channel widening. In this period of time, the maximum distance of bank retreat was up to several tens of meters in the most upstream of the uplift reach mainly resulted from plane-slide failure because of the toe erosion in the river bank. Along the gorge-like channel of the uplift reach, the major failure process of the river banks was collapse of overhanging rock mass due to toe erosion; the channel generally widened just a few meters.

Original languageEnglish
Title of host publicationScour and Erosion IX - Proceedings of the 9th International Conference on Scour and Erosion, ICSE 2018
EditorsYeh Keh-Chia
PublisherCRC Press/Balkema
Number of pages1
ISBN (Print)9780367074678
StatePublished - 1 Jan 2019
Event9th International Conference on Scour and Erosion, ICSE 2018 - Taipei, Taiwan
Duration: 5 Nov 20188 Nov 2018

Publication series

NameScour and Erosion IX - Proceedings of the 9th International Conference on Scour and Erosion, ICSE 2018

Conference

Conference9th International Conference on Scour and Erosion, ICSE 2018
CountryTaiwan
CityTaipei
Period5/11/188/11/18

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