Effect of Rainfall, Runoff and Infiltration Processes on the Stability of Footslopes

Hung-En Chen,Tung-Lin Tsai,Yen-Yu Chiu,Jinn-Chuang Yang

doi:10.3390/w12051229

Abstract

To analyze the effect of runoff on shallow landslides, a model coupling one-dimensional rainfall–runoff and two-dimensional infiltration was established to simulate rainfall, infiltration, and runoff processes. Based on Bishop’s limit equilibrium method, the slope failure of a hypothetical footslope was studied. First, conditions with and without inflow were compared. The results reveal a remarkable difference in factors of safety (FS) between the two conditions, suggesting that considering the effect of runoff is crucial for landslide modeling. In terms of a series of tests of the various magnitudes, durations, lag-time, and peak position of the hydrograph, analyses show that larger inflow leads to more accumulated infiltration and triggers landslides earlier. A long-term duration inflow decreases the stability more than short intensive inflow does. With subsequent surface inflow, slope failure may occur after rainfalls stop, owing to the inflow, and the shape of inflow hydrographs could slightly affect the variance in FS. Results also indicate the necessity of considering the surface runoff when using a numerical model to analyze landslide, particularly on a footslope.

Highlights

Landslides occur in numerous locations worldwide and present serious threats to lives and the economy
With the mechanism greatly simplified in the earliest studies, landslide models have gradually progressed in recent decades and currently include more mechanisms
The theory underlying 1D rainfall–runoff, 2D infiltration equation, and slope stability analysis is briefly described

Summary

Introduction

Landslides occur in numerous locations worldwide and present serious threats to lives and the economy. There is a general consensus that rainfall is the most common external factor that stimulates shallow landslides. The mechanism underlying rainfall-induced landslides has been widely studied and discussed in recent decades [1,2]. A relationship between water and landslides, known as “landslide hydrology,” has been proposed [2]. Water can originate from many sources, such as precipitation, snowmelt, surface water and groundwater. The groundwater seepage has been broadly and deeply analyzed using numerical models, wherein different soil conditions and facilities have been considered [3,4,5,6,7]. It is difficult to completely reproduce the mechanism underlying rainfall-triggered shallow landslides using a numerical model. With the mechanism greatly simplified in the earliest studies, landslide models have gradually progressed in recent decades and currently include more mechanisms. Iverson [8], Baum et al [9], and Tsai and Yang [10]

Objectives

Methods

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Conclusion