Systematic documentation of landslide events in Limbe area (Mt Cameroon Volcano,SW Cameroon): geometry,controlling, and triggering factors |
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| Authors: | V B Che M Kervyn G G J Ernst P Trefois S Ayonghe P Jacobs E Van Ranst C E Suh |
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| Institution: | (1) Department of Geology and Environmental Science, University of Buea, Buea, Cameroon;(2) Department of Geography, Vrije Universiteit Brussels, Free University of Brussels, Brussels, Belgium;(3) Department of Geology and Soil Science, Ghent University, Ghent, Belgium;(4) Royal Museum for Central Africa, Tervuren, Belgium |
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| Abstract: | Limbe town and surrounding areas, on the SE foot slopes of the active Mt Cameroon Volcano, have experienced numerous small-scale
shallow landslides within the last 20 years. These resulted in the loss of ~30 lives and significant damage to farmland and
properties. Landslides and their scars are identified in the field, and their geometry systematically measured to construct
a landslide inventory map for the study area. Specific landslides are investigated in detail to identify site-specific controlling
and triggering factors. This is to constrain key input parameters and their variability for subsequent susceptibility and
risk modeling, for immediate local and regional applications in land-use planning. It will also enable a rapid exploration
of remediation strategies that are currently lacking in the SW and NW regions of Cameroon. Typical slides within the study
area are small-scale, shallow, translational earth, and debris slides though some rotational earth slides were also documented.
The depletion zones have mean widths of 22 m ± 16.7 m and lengths of 25 ± 23 standard deviation. Estimated aerial extents
of landslide scars and volume of generated debris range from 101 to 104 m2 and 2 to 5 × 104 m3, respectively. A key finding is that most slope instabilities within the study area are associated with and appear to be
exacerbated by man-made factors such as excavation, anarchical construction, and deforestation of steep slopes. High intensity
rainfall notably during localized storms is the principal triggering factor identified so far. The findings from this case
study have relevance to understanding some key aspects of locally devastating slope instabilities that commonly occur on intensely
weathered steep terrains across subtropical Africa and in the subtropics worldwide and affecting an ever denser and most vulnerable
population. |
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