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

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 (F s ). 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.

The effect of landslide on soil organic carbon stock and biochemical properties of soil

“…In the previous studies, the authors focused on the assessment of the relationship of soil properties with the possibility of landslides (Meisina 2006;Kitutu et al 2009). The studies performed mainly concentrated on landslides in the tropical zone (Shiels et al 2006;Mugagga et al 2012), while there are no similar studies in the temperate climate zone. The aim of the study was to present variability of content and quality of soil organic matter on the landslide surface.…”

Suitability of Kabanyolo Soils for Fruit and Vegetable Production

“…According to Mugagga et al [27], the percentage of clay, in particular, gives a clear indication of the problem nature of the soils. A 10% clay threshold has been used as an indicator of the expansion potential, whilst 32% clay content exhibits extreme expansion potential [28].…”

The Effect of Land Use on Carbon Stocks and Implications for Climate Variability on the Slopes of Mount Elgon, Eastern Uganda

“…The main causes of this are logging, clearance for agriculture and wood fuel collection (FAO 2010). The deforestation in Mt Elgon began in the 1960s (Kitutu 2004) and since then most of the local forests outside the National Park, including all forests below 2000M elevation have been cleared and converted to agricultural land (Mugagga et al, 2011).…”

“…However, deforestation and rapid population growth rates have led to reduced fallow periods and widespread degradation on the slopes of Mount Elgon (Muwanga et al, 2001;Breugelmans, 2003;Bamutaze, 2004;Glade and Crozier, 2004;Kitutu et al, 2004;Knapen et al, 2006;Nabalegwa, 2008: Kitutu et al, 2009;Mugagga et al, 2010;Barasa and Kakembo, 2013). It is noteworthy that mountain ecosystems are particularly sensitive to International Journal of Regional Development ISSN 2373-9851 2015 anthropogenic impacts and the loss of vegetation cover inevitably alters mountain hydrology and has implications for local and regional climate variability (Beniston, 2003;IPCC, 2007a,b;Mugagga et al, 2011).…”

“…Understanding of the possible effects of past and present day land use cover change on soil organic carbon and land degradation is not only scientifically important, it is also a prerequisite for the development of a sustainable land use policy on the slopes of Mount Elgon that will anchor adaptation to climate change strategies in mountain environments (Mugagga et al, 2011). The purpose of the study was to carry out a comprehensive analysis of land use/cover change, its impact on soil organic carbon and implications for climate variability on the slopes of Mt.…”