Characterization and Hydrological Analysis of the Guarumales Deep-Seated Landslide in the Tropical Ecuadorian Andes

Alexandra Urgilez Vinueza,Pablo Guzman,Mark Bakker,Jessica Robles,Thom Bogaard

doi:10.3390/geosciences10070267

Alexandra Urgilez Vinueza, Pablo Guzman + Show 3 more

Open Access

https://doi.org/10.3390/geosciences10070267

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Journal: Geosciences	Publication Date: Jul 10, 2020
Citations: 2	License type: CC BY 4.0

Affiliation: Delft University of Technology

Abstract

The high landslide risk potential along the steep hillslopes of the Eastern Andes in Ecuador provides challenges for hazard mitigation, especially in areas with hydropower dams and reservoirs. The objective of this study was to characterize, understand, and quantify the mechanisms driving the motions of the Guarumales landslide. This 1.5 km2 deep-seated, slow-moving landslide is actively moving and threatening the “Paute Integral” hydroelectric complex. Building on a long time series of measurements of surface displacement, precipitation, and groundwater level fluctuations, we analyzed the role of predisposing conditions and triggering factors on the stability of the landslide. We performed an analysis of the time series of measured groundwater levels and drainage data using transfer functions. The geological interpretation of the landslide was further revised based on twelve new drillings. This demonstrated a locally complex system of colluvium deposits overlying a schist bedrock, reaching up to 100 m. The measured displacement rates were nearly constant at ~50 mm/year over the 18 years of study. However, the measurement accuracy and time resolution were too small to identify possible acceleration or deceleration phases in response to hydro-meteorological forcing. The groundwater and slope drainage data showed a lagged response to rainfall. Finally, we developed a conceptual model of the Guarumales landslide, which we hope will improve our understanding of the many other deep-seated landslides present in the Eastern Andes.

Highlights

Landslides are the movement of earth down the slope of a hill or mountain
The objective of this study was to characterize, understand, and quantify the mechanisms interfering with the stability of the Guarumales landslide
We showed that the movement of the landslide was continuous on an annual timescale, both in the direction and horizontal displacement rate, and there were no significant changes over the last 18 years

Summary

Introduction

Landslides are the movement of earth down the slope of a hill or mountain. Gravity is the primary driver of this movement, but water and other factors, including anthropogenic influences, may play a role as well [1]. There are several classification systems that describe the characteristics of the movement, including timing and predisposing and triggering factors [1,2,3,4,5]. Apart from the morphological classifications of landslides, Brönnimann [6] proposed a classification system where the hydrogeological ‘architecture’ and predisposing conditions for landslide occurrence are defined by the permeability and degree of saturation of the slope layers. This approach allows researchers to assess the hydrogeological predisposing conditions and triggering mechanisms behind specific slope instabilities, and to characterize different landslides under the same hydrogeological conditions.

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