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Flume experiments in the development of crevasse-splay deposits; transition from asymmetric-to-symmetric geometry

Taichi Kato, Masaki Yamada, Hajime Naruse and Sakai Yuichi
Flume experiments in the development of crevasse-splay deposits; transition from asymmetric-to-symmetric geometry
Journal of Sedimentary Research (August 2023) 93 (11): 825-839

Abstract

Crevasse-splay deposits play an important role in the reconstruction of the magnitude of past flood events and in understanding the behavior of river systems. Despite the extensive studies conducted on the geometry and facies of crevasse-splay deposits, their spatiotemporal developmental processes have remained insufficiently understood. In this study, scaled flume experiments were conducted to study the relationship between the developmental processes of crevasse splays and their characteristics. An experimental flume was set up in a tank to simulate the 2019 Chikuma River flood, Central Japan event. To model the overbank flow, an opening was created on the side of the flume's wall through which the flow flooded onto a horizontal acrylic plate. The sediment used in the experiments consisted of particles with grain sizes of approximately 0.3 and 0.1 mm, which were determined to be equivalent to bedload gravel and suspended sand in a real-scale river using dimensional analysis. The results of the experiments revealed three important findings: (1) Crevasse-splay deposits initially developed an asymmetric shape extending downstream of the main river channel but gradually showed a symmetric geometry. The river mainstream initially influenced the direction of the inundation flow, but channel bifurcations after the deposition of the sediment piles later changed the geometry of splays into a more symmetric shape. (2) Crevasse-splay deposits developed in two distinct regions (proximal and distal splay), corresponding to sediment transport by bedload and suspended load, respectively. These two regions are commonly observed in the actual field scale. (3) The original overbank flow was a sheet flow without channels, which caused coarse-grained sediments to be spread over a wide area. Subsequently, the accumulation of coarse sands in the developed channel interiors resulted in the buildup of finer-grained sediments upstream of the proximal splay. Thus, the proximal splay deposits became slightly coarse downstream, whereas they rapidly became fine at the boundary with the distal splay. These findings indicate that the characteristics of crevasse-splay deposits vary with the landform's development stage, thus providing a basis for interpreting their depositional facies.


ISSN: 1527-1404
EISSN: 1938-3681
Serial Title: Journal of Sedimentary Research
Serial Volume: 93
Serial Issue: 11
Title: Flume experiments in the development of crevasse-splay deposits; transition from asymmetric-to-symmetric geometry
Affiliation: Shinshu University, Graduate School of Science and Technology, Nagano, Japan
Pages: 825-839
Published: 20230814
Text Language: English
Publisher: Society for Sedimentary Geology, Tulsa, OK, United States
Number of pages: 53
References: 51
Accession Number: 2023-061202
Categories: Sedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
Secondary Affiliation: Kyoto University, Graduate School of Science, JPN, JapanUtsunomiya University, Department of Forest Science, JPN, Japan
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2023, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 202337
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