Debris Flow Management along the National Highway in Korea
Seung-Hyun KIM#+, Byung-Suk PARK, Yong-Hoon WOO
Korea Institute of Civil Engineering & Building Technology, Korea, South

In Korea, there are about 70% of mountainous areas and most landslides are rock failure. Nevertheless, debris flow sometimes occurs due to heavy rain. Debris flow occurs in the blink of an eye, the damage area is very large, so it is highly likely to cause casualties, so systematic management is needed. The management of debris flow was strengthened nationwide in the wake of the landslide at Umyeonsan Mountain in Seoul, but CSMS(Cut Slope Management System project by Ministry of Land, Infrastructure & Transport(MOLIT)) did not manage debris flow before 2013. The mountainous area where debris flow occur was under the jurisdiction of the Korea Forest Service(KFS), and road landslides were said to have nothing to do with debris flow. The need for management has emerged as torrential rains caused by global warming have increased the number of debris flow invading roads. In the management of roadside debris flow, there was initially confusion in the management of debris flow and in the setting of survey items. We made several key tasks to solve this issue ; To prepare items and checklists for debris flow field surveys, prioritization of investigation considering risk and damage levels of debris flow, classification of countermeasures to prevent debris flow damage & establishment of a cooperative system between MOLIT and KFS. KFS already operates geohazard map for damage prediction of debris flow and geohazard map for Integration Debris flow, taking into account topography, geology, and population. But this map itself does not take into account roads into account. Nevertheless, we think this map can play an important role in extracting debris flow risk areas along national highway. In 2021, we're going to find and list the overlapping parts of the existing debris flow hazard map and roads. We are going to conduct a joint investigation on the debris flow points where the risk is high and make a countermeasure. Of course, it will be possible to operate the debris flow checklist and investigation priority techniques.