Estimation of Risk Thresholds for a Landslide in the Three Gorges Reservoir Based on a KDE-Copula-VaR Approach

Shen Zhang,Huiming Tang,Junwei Ma

doi:10.1155/2020/8030264

Abstract

The Three Gorges Reservoir area, one of the most landslide-prone areas in China, is characterized by widely distributed deep-seated landslides exhibiting creep deformation due to rainfall and reservoir fluctuation. Thresholds, which are a key component for a reliable landslide early warning system, are still lacking for the prediction of movements of deep-seated reservoir landslides with creep deformation because information about reservoir fluctuation indicators is lacking, uncertainty is ignored, and binary output is provided. The risk threshold, defined as the tolerance criteria for risks that will lead to action, is an effective measure of the degree of uncertainty. In the present study, a hybrid approach utilizing kernel density estimation, a copula function, and the value at risk is proposed for the estimation of the risk threshold for the Baishuihe Landslide, a typical deep-seated landslide in the Three Gorges Reservoir area. Historical observations over approximately 15 years including rainfall, reservoir fluctuation, and landslide velocity were used to extract the risk threshold. A three-level risk threshold describing the minimum magnitudes of rainfall and reservoir fluctuation for changing the landslide movement state under three confidence levels was developed. A three-level risk response procedure, including risk responses in yellow alert, orange alert, and red alert, is proposed for risk management. Given its successful application, the present approach can be used to estimate the risk threshold for deep-seated landslides.

Highlights

The movement and failure of landslides can cause significant societal and economic losses
Due to rainfall and reservoir fluctuation, the Three Gorges Reservoir area is highly affected by the creep deformation of deep-seated landslides
Few attempts have been made to estimate early warning criteria that describe the magnitudes of rainfall and reservoir fluctuation for changing the landslide movement state

Summary

Introduction

The movement and failure of landslides can cause significant societal and economic losses. In the 1980s, a global rainfall threshold for shallow landslides and debris flows was proposed based on 73 cases [8]. The available rainfall thresholds can be classified according to both the estimation approaches that are used (i.e., physically based approaches or empirical approaches) and the rainfall variables that express the threshold (e.g., rainfall duration, cumulative event rainfall, rainfall intensity, or antecedent rainfall) [22]. These rainfall thresholds have been widely applied due to the advantage of determining the timing for the occurrence of shallow landslides

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