Features of crevasse splay deposits and sedimentary processes associated with levee breaching due to the October 2019 flood of the Chikuma River, Central Japan

Yamada, Masaki; Naruse, Hajime; Kuroda, Yugo; Katô, Takeo; Matsuda, Yuichi; Shinozaki, Tetsuya; Tokiwa, Tetsuya

doi:10.1007/s11069-023-06122-7

Cited by 2 publications

(5 citation statements)

References 39 publications

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“…In addition, the upstream pile was coarse grained because initial unconfined flooding formed the central part of this pile, while the downstream pile was formed from the overflowing current from the confined crevasse-channel flows. The same feature was observed in the Hoyasu area (Yamada et al 2023). Other studies also described the same feature (e.g., Florsheim and Mount 2002;Arnaud-Fassetta 2013).…”

Section: Characteristic Features Of the Crevasse-splay Depositsupporting

confidence: 73%

“…Crevasse-splay deposits were studied near the breached levee of the Chikuma River in the Hoyasu area, Nagano Prefecture, central Japan, by Yamada et al (2023) (Fig. 1).…”

Section: Geomorphologic Setting and 2019 Flood Eventmentioning

confidence: 99%

“…The average river slope in the study area is 0.1%, and the floodplain is approximately 2160 m wide. The time of overtopping and levee breach was caclulated through a closed-circuit television camera placed on the levee and from the water-level records at the upstream and downstream gauging stations (Investigation Committee on the Chikuma River Levee 2020; Yamada et al 2023). The river water overflowed the levee revetment at 0:55 AM on October 13.…”

Section: Geomorphologic Setting and 2019 Flood Eventmentioning

confidence: 99%

“…An experimental tank at Kyoto University was used to conduct flume experiments to model the crevasse channel and associated deposits at the study site. The experimental setup was designed to be an approximately 1/200 scale for the measured values of the river width and depth at the study site of Yamada et al (2023). The flume was made of acrylic boards 8 cm wide and 20 cm high (Fig.…”

Section: Experimental Settingmentioning

confidence: 99%

“…For the experimental conditions, the nondimensionalized hydraulic and sedimentary conditions of the October 2019 flooding of the Chikuma River in Nagano Prefecture, central Japan (Yamada et al 2023) was used. The gauging stations recorded the hydraulic conditions of the flooding event, whereas the field surveys revealed significant variations in the thickness and grain-size distributions of gravelly and sandy crevasse-splay deposits formed in the area of the breached levee (Yamada et al, 2023). Therefore, the conditions of this flooding event are suitable for constraining the flume experiments to better understand the processes involved in the transport and deposition of sediments during a flooding event.…”

Section: Introductionmentioning

confidence: 99%

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

Kato,

Yamada,

Naruse

et al. 2023

Journal of Sedimentary Research

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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 experi ments 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.

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Section: Characteristic Features Of the Crevasse-splay Depositsupporting

confidence: 73%

“…Crevasse-splay deposits were studied near the breached levee of the Chikuma River in the Hoyasu area, Nagano Prefecture, central Japan, by Yamada et al (2023) (Fig. 1).…”

Section: Geomorphologic Setting and 2019 Flood Eventmentioning

confidence: 99%

Section: Geomorphologic Setting and 2019 Flood Eventmentioning

confidence: 99%

Section: Experimental Settingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

Kato,

Yamada,

Naruse

et al. 2023

Journal of Sedimentary Research

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Understanding paleo-earthquakes in the Kuril Trench based on Late-Holocene tsunami deposits in the distal region from wave sources, northern Hidaka, Hokkaido, Japan

Nakanishi,

Ashi,

Okamura

et al. 2024

PLoS ONE

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Geological evidence, such as tsunami deposits, is crucial for studying the largest rupture zone of the Kuril Trench in Hokkaido, Japan, due to its poor historical record. Although 17th-century tsunami deposits are widely distributed across Hokkaido, the presence of multiple wave sources during that period, including the collapse of Mt. Komagatake, complicates the correlation with their wave sources. Understanding the regional distribution of these tsunami deposits can provide valuable data to estimate the magnitude of megathrust earthquakes in the Kuril Trench. The northern part of Hidaka, Hokkaido, where tsunamis from multiple wave sources are expected to overlap, is distant from the Kuril Trench. To clarify the depositional history of tsunami deposits in such distal areas, evaluating the influence of the depositional environments on the event layer preservation becomes even more critical. We conducted field surveys in Kabari, located in the northern Hidaka region, identifying three sand layers from the 10th to the 17th century and two layers dating beyond 2.3 thousand years ago. The depositional ages of most sand layers potentially correlate with tsunami deposits resulting from the Kuril Trench earthquakes. Utilizing reconstructed paleo-sea level data, we estimated that most sand layers reached approximately 2 m in height. However, it is noteworthy that the latest sand layer from the 17th century exhibited an unusual distribution, more than 3 m in height. This suggests a different wave source as the Mt. Komagatake collapse. The discovery of multiple sand layers and their distributions is crucial to constraining the maximum magnitude of giant earthquakes in the Kuril Trench and understanding the volcanic tsunami events related to Mt. Komagatake.

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Features of crevasse splay deposits and sedimentary processes associated with levee breaching due to the October 2019 flood of the Chikuma River, Central Japan

Cited by 2 publications

References 39 publications

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

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

Understanding paleo-earthquakes in the Kuril Trench based on Late-Holocene tsunami deposits in the distal region from wave sources, northern Hidaka, Hokkaido, Japan

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