Rapid vegetation recovery at landslide scars detected by multitemporal high-resolution satellite imagery at Aso volcano, Japan

Abstract

Vegetation cover is an important factor in hillslope stability and landslide susceptibility. The objective of this study is to explore vegetation recovery in rainfall-induced and coseismic landslide scars at the Aso volcano in Japan. We focus on the temporal changes and effect of topography on vegetation recovery using multitemporal satellite images of RapidEye from 2010 to 2019 and PlanetScope from 2016 to 2020 and finer spatial resolution images of unmanned aerial vehicles (UAVs). The study area is characterized by semi-natural grassland and frequent landslide events triggered by heavy rainfall in 2012 and the 2016 Kumamoto earthquake. This study validates grass vegetation recovery using the normalized difference vegetation index (NDVI) and NDVI ratio, which represents the relative difference in NDVI between the landslide scars and grass areas. The results show a distinct decrease in the NDVI ratio at landslide scars after the heavy rainfall and Kumamoto earthquake. The NDVI ratio rapidly increases in landslide scars after the events. The results indicate that NDVI at both landslide scars will reach the same level as the pre-landslide grass vegetation within 12 years. The slope aspect direction determines the topographic effects of grass vegetation recovery. The north- to west-facing landslide scars seemed to experience rapid grass vegetation recovery.