Wednesday, May 29, 2024

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was conducted to observe the effects of vegetation on debris flow dynamics The purpose of the Jinbu debris flow experiment in South Korea was to study how vegetation affects the dynamics of debris flow.


The initiation of the debris flow front at Jinbu in South Korea.

The author of The Landslide Blog is Dave Petley, a highly respected expert in the field of landslide research and control.

Image of a landslide partially covered with a transparent sand-colored overlay and the words “The Landslide Blog,” centered, in white

In South Korea, one of the main challenges is dealing with debris flows in highland regions, often caused by intense precipitation. In 2011, a debris flow devastated a residential area on Mt. Umyeon in Seoul, resulting in significant damages and 16 deaths. As a response, South Korea has implemented a proactive program to simulate debris flows, study their behavior, and develop effective methods for prevention.

An effective method that has been utilized involves physically measuring debris flows in real-life scenarios, which aids in fine-tuning models. Several organizations are actively researching in this field, such as the renowned flume at the US Geological Survey, the experimental facilities at Hong Kong University of Science and Technology, the currently-being-built large-scale flume in Kunming, China, and the well-known Illgraben site managed by WSL. Flumes typically employ larger amounts of material on straight channels for comparison.

A unique and innovative approach has been implemented in South Korea. A location in Jinbu, Gangwon Province was chosen for experimental purposes. The site includes a natural channel and six tributaries, with a main channel length of 824 m, which is representative of a debris flow channel in the region’s highlands. To prevent any negative effects downstream, a check dam has been installed at the end of the channel.

The Journal Landslides recently published a new paper (Yune et al., 2023) that describes the facility and one of the experiments. The paper includes an image illustrating the site’s configuration.

The configuration of the debris flow channel at Jinbu in South Korea.

The image depicts the layout of the debris flow channel at Jinbu in South Korea, as presented in Yune et al.’s (2023) study.

³/s of water to be released

A large concrete box with a gate has been built at the start of the primary waterway, enabling the discharge of 346 m³/s of water.3 of soil and 268 m3

The channel has been designed to store and discharge water. In the steeper section of the channel, a geotextile has been added to strengthen the bed and prevent erosion, ultimately protecting the channel. The flow of water is then allowed to naturally continue down the channel. The channel is equipped with various instruments, such as sensors and cameras, and is surveyed using lidar before and after experiments.

In a study conducted by Yune et al. (2023) at the Jinbu facility, an experiment was conducted that involved placing logs along the channel and observing their effect on flow dynamics. Interestingly, the logs were entrained into the flow during the experiment.

Unfortunately, the additional material accompanying the article includes footage of the debris flow’s journey through the Jinbu channel. However, it appears that this footage has not been shared online. The attached image displays the front of the debris flow near the starting point, offering insight into its speed.

The arrival of the debris flow front at Jinbu in South Korea.

The debris flow front reaching Jinbu, South Korea. Image from a video by Yune et al. (2023).

During the experiment, the debris flow picked up speed in the steeper section of the channel, reaching a maximum velocity of 16.6 meters per second. As the slope decreased further downstream, the velocity of the debris flow also decreased. This flow caused erosion in the faster-moving areas of the bed.

There is a necessity for diverse methods in predicting debris flows. This unique approach is highly valuable, offering understanding on how the flows interact with the terrain and sediment formations. The capability to simulate large-scale flows is impressive.

This is an excellent combination of science and enjoyment.

Reference

In 2023, Yune, CY., Kim, BJ., Jun, KJ. and colleagues conducted a real-scale experiment on debris flow in a natural gulley. Their findings and lessons learned were published in the journal Landslides. The study can be found at https://doi.org/10.1007/s10346-023-02134-3.

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Text © 2023. The authors. CC BY-NC-ND 3.0

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