Assessement of Rockfall Hazard in the Northeast Region of Ulleung-Do

Abstract

The geology of Ulleung-Do is dominated by volcanic rocks with low strength and trachytic rocks with high strength but containing vertical joints that yield easily. Consequently, rockfalls along roadcuts are a major geological hazard, with the potential to affect the ring road of Ulleung-Do. In this study, we performed three types of rockfall hazard-risk assessment on the 3-km-long section of the ring road expected to have the highest possibility of rockfall. We used a rockfall ranking sheet in a roadside landslide hazard map, the Slope Stability Inspection Manual for National Highways (Japan), and a rockfall hazard rating system for inspection from the Japan Highway Public Corporation. We also employed the evaluation criteria of 'RHRS' developed by the Federal Highway Administration (FHA). An analysis of roadcuts at 27 sites with regard to geographic and geological conditions resulted in the identification of three classes of rockfall hazard (high, medium, and low). Of note, over 74% of slopes were assessed as high-and medium-class. Finally, a rockfall hazard map of the northeast region of UlleungDo was produced based on the evaluation results.

Processes driving understory community dynamics in Ulleungdo Island broadleaved forest, South Korea

“…Events with ≥300 mm precipitation occurred three times between 2009 and 2011, and events with ≥400 mm precipitation occurred three times between 2014 and 2016. Owing to its location and topographic features (high elevation mountainous terrain), Ulleungdo Island is frequently affected by landslides and rock-falls caused by heavy rainfall events (Lee et al, 2018;Seo et al, 2012). The study site, located at the inner caldera, is alluvial land consisting of sedimentary layers approximately 50-100 m thick.…”