FATES-HYPERS 宿命FATES-HYPERS 宿命

Sediment sinks at depositional terrace in upper reach of the Gaoping Canyon

Cheng-Shing Chiang a, and Ho-Shing Yub

a Hsiuping Institute of Technology, Taichung, Taiwan, ROC

b Institute of Oceanography, National Taiwan University , Taipei, Taiwan, ROC

FATES-HYPERS 宿命FATES-HYPERS 宿命

Introduction The capability of canyons:

Sediment transfer Erosion Deposition sediments are trapped in terraces temporary or perennial sediment traps types of terrace morphology terrace formation and evolution

FATES-HYPERS 宿命FATES-HYPERS 宿命

Introduction

Sediments are traped within particular morphologies called terraces, with reference to fluvial environment. (Cirac et al.,2001; Gaudin et a.,2006)

FATES-HYPERS 宿命FATES-HYPERS 宿命

What do we need to know about terrace?

morphology featuressinkprocesses

In terms of source to sink

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Four types of terrace in Capbreton Canyon

(Gaudin et al., 2006)(Gaudin et al., 2006)

Horseshoe terraces (T1)• that is characterized by a flat, arcuate outer pattern surrounding an elongated and rounded

topographic high.

Hemispherical terraces (T2)• with a flat top and have an arcuate pattern

Rounded elongated terraces (T3)• that is located inside meander loops and with a rounded top

Flat elongated terraces (T4) that is flat and elongated parallel to the thalweg axis.

FATES-HYPERS 宿命FATES-HYPERS 宿命

Evolution of Capbreton Canyon morphology

(Gaudin et al., 2006)(Gaudin et al., 2006)

T1 : Horseshoe terraces

T3 : Rounded elongated terraces

T4 : Flat elongated terraces

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Types of terrace in the world

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Cross-section morphology

FATES-HYPERS 宿命FATES-HYPERS 宿命

Cross-section 340-1

terrace

FATES-HYPERS 宿命FATES-HYPERS 宿命

Point bar terrace? Slide- or slump-related terraces ?

Seismic profile 340-1

terrace

FATES-HYPERS 宿命FATES-HYPERS 宿命

Cross-section 340-4

Steep wall

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Slide- or slump-related terraces

FATES-HYPERS 宿命FATES-HYPERS 宿命

Depositional terraces occurred in meander bend

FATES-HYPERS 宿命FATES-HYPERS 宿命

Horseshoe terracesT1

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Chirp sonar profile C3

T1

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Elongated terrace

T3

No cut-off presently

FATES-HYPERS 宿命FATES-HYPERS 宿命

Compare with the Compare with the Capbreton canyonCapbreton canyon

arcuate pattern

FATES-HYPERS 宿命FATES-HYPERS 宿命

ConclusionTerraces are well observed in the meandering segment of the canyon and mainly in inner parts of the meander bends, showing distinct depositional features of spill-over sediments to form levees.Four major types of terrace morphology have been established in the study area: Slide- or slump-related terraces, point bar terraces, horseshoe terraces (T1) and elongated terraces (T3).

FATES-HYPERS 宿命FATES-HYPERS 宿命

We reveal the temporary sink of terrace of the Gaoping Canyon under the highstand of sea level as characterized by a direct sediment source from a small mountainous river with high sediment load.

FATES-HYPERS 宿命FATES-HYPERS 宿命

Thanks, and your comments are welcomed