Simulate landslide activities during flood season 2020 - 2021 in Phong Nha - Ke Bang National Park

Abstract

Abstract Research highlights in study area, there are various small-scale landslide points occurred and located surround from major landslide point with already 42 field-investigated points. The core zone of study area has the gravity displacement coefficient (Kg) by 0.0006, the buffer zone has Kg by 0.0033, all of them are weak and relative stable. The core zone of the National Park has more than 60 landslide points with total area of 81.19 hectares, and total landslide soil volume is over 2.6 mil m3. The largest landslide volume in study area is about 2.4 mil m3, with added 14 large-scale lanslide volume from 1,000 to 65,000 m3. In particular, a number of slopes occurred consecutively during flood seasons in years of 2020 - 2021. Landslide activities strongly affecting the integrity and aesthetic value of Phong Nha – Ke Bang (PNKB) National Park with calculation results, for the largest landside point during rainny season in October, 2020, show that the sliding soil blocks have displaced more than 130 m, with low factor of safety (FS) by 0.32 and the total sliding soil volume is 2.1 million m3, also consistent with field monitoring data and analysis of remote sensing images (2.4 mil m3).