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Natural Hazards

, Volume 60, Issue 3, pp 1113–1131 | Cite as

A characterisation of the physical properties of soil and the implications for landslide occurrence on the slopes of Mount Elgon, Eastern Uganda

  • F. Mugagga
  • V. Kakembo
  • M. Buyinza
Original Paper

Abstract

Soil properties of major landslides that occurred recently on the mid-altitude slopes of Mount Elgon, eastern Uganda were analysed. A mudflow, located at the Kitati protected forest site, and two deep debris flows on the Nametsi and Buwabwala deforested steep slopes (36°–58°) were surveyed. In order to test the hypothesis that ‘soils at the landslide sites are particularly ‘problem soils’ and thus prone to landslides’, the following analyses were undertaken: particle size distribution, Atterberg limits, shear strength and factor of safety (Fs). Soils at the Kitati and Buwabwala sites exhibited expansive potential, owing to clay contents well above 20%. A clay content exceeding 32% was identified at the Nametsi debris flow site implying an extremely high expansive potential of the soil. High liquid limits (LLs) at Kitati (59%) and Buwabwala (53%) meant that the soils qualified as vertisols susceptible to landslides. High plasticity indices (PIs) (averaging 33%) also confirmed the vertic nature of soils at the Nametsi debris flow site. Whereas the value of F s  < 1 for the Kitati site signifies an inherently unstable slope, Nametsi and Buwabwala are supposedly stable slopes (F s  > 1). Despite this finding, the stable sites could be described as only conditionally stable because of the interplay of various physical, pedological and anthropogenic factors. The results point to the fact that soils at the landslide sites are inherently ‘problem soils’ where slope failure can occur even without human intervention. Therefore, the hypothesis that soils at three landslide sites are inherently ‘problem soils’ and prone to landslides, is accepted.

Keywords

Atterberg limits Clay content Expansive potential Mount Elgon Problem soils Vertic soils 

Notes

Acknowledgments

The authors gratefully acknowledge the research grant from the Department of Research Capacity Development of the Nelson Mandela Metropolitan University, Port Elizabeth and National Research Foundation, South Africa.

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Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  1. 1.Department of GeosciencesNelson Mandela Metropolitan UniversityPort ElizabethSouth Africa
  2. 2.Faculty of Forestry and Nature ConservationMakerere UniversityKampalaUganda

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