Discovering Vegetation Recovery and Landslide Activities in the Wenchuan Earthquake Area with Landsat Imagery.

Cheng Zhong,Peng Gao,Hui Li,Chang Li

doi:10.3390/s21155243

Abstract

Post-seismic vegetation recovery is critical to local ecosystem recovery and slope stability, especially in the Wenchuan earthquake area where tens of thousands of landslides were triggered. This study executed a decadal monitoring of post-seismic landslide activities all over the region by investigating landslide vegetation recovery rate (VRR) with Landsat images and a (nearly) complete landslide inventory. Thirty thousand landslides that were larger than nine pixels were chosen for VRR analysis, to reduce the influence of mixed pixels and support detailed investigation within landslides. The study indicates that about 60% of landslide vegetation gets close to the pre-earthquake level in ten years and is expected to recover to the pre-earthquake level within 20 years. The vegetation recovery is significantly influenced by topographic factors, especially elevation and slope, while it is barely related to the distance to epicenter, fault ruptures, and rivers. This study checked and improved the knowledge of vegetation recovery and landslide stability in the area, based on a detailed investigation.

Highlights

A strong earthquake often causes thousands of landslides, debris flows, and other secondary geohazards, which affects slopes’ stability for a long time [1]
normalized difference vegetation index (NDVI) images from the growing season of each year were generated and fused using the maximum-value composite (MVC) method; secondly, the vegetation damage after the earthquake was estimated by comparing the NDVI images before and after the earthquake; thirdly, the vegetation recovery status was evaluated by calculating the difference between the NDVI right after the earthquake and the NDVI of a following year; a landslide’s activity was estimated roughly according to its vegetation recovery status; fifthly, the influence of the landform factors on vegetation recovery and landslide activity was analyzed; at last, discussion and suggestions for regional landslide stability and mitigation were given
Tens of thousands of landslides triggered by the Wenchuan earthquake are re-activated by heavy and uneven precipitation

Summary

Introduction

A strong earthquake often causes thousands of landslides, debris flows, and other secondary geohazards, which affects slopes’ stability for a long time [1]. Those landslides or instable slopes are re-activated in the following rainy seasons [2,3,4]. Tens of thousands of landslides were triggered by the earthquake and caused tremendous property loss and casualties [9,10,11]. The post-seismic landslide event has attracted extensive attention, as the number, density, area, and casualties of landslides in the event are all much greater than those in other events caused by a single earthquake [12,13]. Several studies forecasted that post-seismic landslide activities will continue for 20 years or more [14,15]

Methods

Results

Conclusion