Monitoring Soil Movement Characteristics of an Area Subject to Land Creeping in the Republic of Korea

Abstract

Land creeping in mountainous regions is a phenomenon describing sediment blocks to move downwards very slowly through a slip surface due to its geographical or geological characteristics. In Republic of Korea, there was few case of land creeping reported, but recently it often is reported because of anthropogenic impacts such as land use changes and constructions in forest sectors. The objective of the current study was to report on monitoring results of a land creeping case in Republic of Korea. The study site was located in Hadong-gun, Gyeonsangnam-do, southern part of Republic of Korea. The land creeping of 2.6 ha area was located on 200–300 m a.m.s.l. and on anorthosite of bedrock. The dominant tree species was oak trees (Quercus mongolica) in above story and bamboo trees (Phyllostachys bambusoides) in underground story. Although the land creeping event was officially reported in April 2015, it appeared to start moving in late 1990s when a reservoir for agricultural use was constructed adjacent to the area. The overflows of the reservoirs by the land creeping can cause secondary damages to downstream resident areas. Soil bulk density, particle size distribution, porosity and hardness have been periodically measured as soil physical properties of the study site. These soil factors can be used as indirect index for vegetation restoration. As a result, there were no significant differences of investigated factors except for soil hardness. Forward plans to focus on monitoring the hardness of the soil. Several 2 sets of poles were installed for monitoring on the size of two tension cracks. The length, width, and depth of tension cracks just varied through monthly measurements from July to December, 2015, but did not tend to increase or decrease. Therefore, we re-arranged and installed poles around the main scar of the land creeping in April, 2016. Now filed survey for identifying detailed geological and geographical characteristics in the area is being carried out, then specific monitoring instruments such as extensometer, groundwater level meter, ground inclinometer and so on will be installed for precise measurement from the result of the field survey.