2:30 PM - 2:45 PM
[HDS11-04] Surface changes of rock slopes in the Hakuba-Daisekkei, northern Japanese Alps
Keywords:rockfall, rock slope failure, SfM, UAV, freezing and thawing
Introduction
In the northern Japanese Alps, rock slope failure has caused mountaineering accidents frequently. In the Hakuba-Daisekkei, rock slope failure with victims occurred in 2005 (Kariya, 2006). However, the process and geomorphological characteristics of rock slope failure are unclear. As a reason, it is difficult to investigate the steep rock slope directly. The purpose of this study is to clarify the process of rock slope failure on different rock types in the Hakuba-Daisekkei using UAV and SfM methods.
Study area
The Hakuba-Daisekkei is a perennial snow patch located at the bottom of the Daisekkei Valley. The valley is a popular mountaineering route to Mt. Hakuba (2932 m asl). More than 10,000 people pass the route every year. Daisekkei Valley is surrounded by Mts. Shakushi and Hakuba. Mt. Hakuba consisted of felsic tuff and tuff breccia. Mt. Shakushi consisted of Felsite. In the Hakuba-Daisekkei, the annual precipitation until summer is high, and it is one of the heaviest snowfall areas in Japan.
Methods
We observed the retreat process of rock slopes using images of UAV, Cessna and aerial photography with SfM (Structure from Motion) technology.
Results and Discussion
We confirmed the difference in the retreat process between Mt. Shakushi and Mt. Hakuba. On the rock slope of Mt. Shakushi, we observed the discriminatory retreat that depended on rock joint density. On the other side, we observed the sudden retreat process with a tension crack opening on the rock slope of Mt. Hakuba. Based on the seasonal changes in the average rate of rockwall retreat and snow distribution, we discussed the effect of the annual freeze-thaw cycle on the collapse and how the development process of gravity-deformed terrain differs in different geological features.
In the northern Japanese Alps, rock slope failure has caused mountaineering accidents frequently. In the Hakuba-Daisekkei, rock slope failure with victims occurred in 2005 (Kariya, 2006). However, the process and geomorphological characteristics of rock slope failure are unclear. As a reason, it is difficult to investigate the steep rock slope directly. The purpose of this study is to clarify the process of rock slope failure on different rock types in the Hakuba-Daisekkei using UAV and SfM methods.
Study area
The Hakuba-Daisekkei is a perennial snow patch located at the bottom of the Daisekkei Valley. The valley is a popular mountaineering route to Mt. Hakuba (2932 m asl). More than 10,000 people pass the route every year. Daisekkei Valley is surrounded by Mts. Shakushi and Hakuba. Mt. Hakuba consisted of felsic tuff and tuff breccia. Mt. Shakushi consisted of Felsite. In the Hakuba-Daisekkei, the annual precipitation until summer is high, and it is one of the heaviest snowfall areas in Japan.
Methods
We observed the retreat process of rock slopes using images of UAV, Cessna and aerial photography with SfM (Structure from Motion) technology.
Results and Discussion
We confirmed the difference in the retreat process between Mt. Shakushi and Mt. Hakuba. On the rock slope of Mt. Shakushi, we observed the discriminatory retreat that depended on rock joint density. On the other side, we observed the sudden retreat process with a tension crack opening on the rock slope of Mt. Hakuba. Based on the seasonal changes in the average rate of rockwall retreat and snow distribution, we discussed the effect of the annual freeze-thaw cycle on the collapse and how the development process of gravity-deformed terrain differs in different geological features.