Susceptibility Analysis of Access Trails to Debris Flows at 12 Waterfalls in Mt. Naeyeon Using a Random Walk Model; 랜덤워크 모델을 활용한 내연산 12폭포 탐방로의 토석류 취약성 분석

초록

Geoparks have been attracting increasing international interest by conserving geologically valuable heritage through education and tourism while contributing to local economies. The 12 Waterfalls of Naeyeonsan, located in the Gyeongbuk Donghaean Geopark, are known for diverse geological forma tions and picturesque landscapes. At the same time, the trails in Naeyeonsan are exposed to debris flows due to their steep slopes and cliffs. However, previous investigations have been limited by the lack of assessment of debris-flow risk on trails and the establishment of trail management systems. Therefore, the aim of the present study is to predict debris-flow runout along the 12 Waterfalls trail of Naeyeonsan by applying a simplified version of the dfwalk model. In this study, initial landslide points were delineated by identifying Grade 1 zone on the landslide hazard map of the Korea Forest Service. The initial debris volume was determined as the product of the mapped Grade 1 zone, and the soil depth was derived from the Z-model. To delineate the travel path and dispersion extent of debris flows, we applied the simple flow routing method and performed 10,000 monte carlo simulations. Based on these simulations, we subsequently estimated debris flow trajectory probabilities. As a result, it was shown that approximately 10% of the roughly 8.5 km Naeyeonsan Course 2 trail is susceptible to debris flows. The analysis indicates that trail sections at seven waterfalls are highly susceptible, while trail sections at five waterfalls have relatively low susceptibility. These findings are expected to serve as fundamental data for the identification of debris-flow susceptible areas within geoparks and for establishing evacuation routes in advance.

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