In 2003, a number of landslides occurred in the Ntchenachena and the Chiweta
Areas of the Rumphi District in Northern Malawi, and in the Livilivi/Mvai
Catchments of Ntcheu District in Central Malawi. The landslide events caused
significant damage to crops, farmland, livestock and infrastructure. Worse still,
they caused the death of four people. The high density of landslides
occurrences suggested instability of the slopes of these areas.
In light of these landslides, this study set out to assess the slope stability status of
the areas. The study addressed landslide mapping and classification of observed
events; assessment of the causes and contributing factors; assessment of the
socio-economic and environmental impacts of the events; exploration of
traditional knowledge, beliefs and peoples perceptions surrounding landslides;
determination of the coping strategies; and development of mitigations to
landslides as geo-hazards.
This study involved a landslide inventory of all observed This study involved a landslide inventory of all observed events. The physical
characteristics of the terrain influencing slope instability were measured. The
characteristics recorded included slope length, angles, aspect and altitude, and
channel dimensions. Landslides were classified based on the type of movement,
degree of stabilisation, and age, and materials involved in the movement. Soil
samples were collected, using core and clod sampling methods and were
tested for plastic limit, liquid limit, plasticity index, bulk density, hydraulic
conductivity, aggregate stability, and particle sizes. Structural rock weaknesses
were also measured. Vegetation data was collected, using the quadrant
method and was analysed for average diameters at stump and breast height,
canopy cover, and height. Questionnaires/surveys were used to assess local
knowledge and perceptions towards landslides. A SPSS statistical package was
used to analyse both social and physical data. It was found that 131 landslides had occurred of which 98 were in the Rumphi
District, Northern Malawi and 33 occurred in the Ntcheu District, Central Malawi.
The variations were observed to be due to the degree of disturbance of the
physical environment. The Ntchenachena Area, with the highest density (88),
was under cultivation and the afro-montane vegetation had been completely
destroyed. The deepest channels were observed in the Ntchenachena Area,
partly because of the deep chemical weathering of the basement. In contrast,
the rest of the areas had thin soils. Slope aspect and type were found to be of
little significance in the occurrence and spatial distribution of the events.
The analysis of data suggested that the events were caused by liquefaction of
sand and silt fractions due to high and prolonged precipitation. The evidence
from the Chiweta and the Mvai Areas suggests that high cleft water pressure
between rock and soil masses might have caused some failures. However,
destruction of vegetation, cultivation on marginal lands, high slope angle,
weathering of the basement, and slope cutting contributed to the instability.
The study also noted that the Ntchenachena, the Mvai and the Livilivi Areas
largely require soft solutions to the landslide problem. These include afforestation,
proper siting of houses, and restricting settlement activities in danger-prone
areas. Income generating activities to reduce poverty, community participation
in natural resources management and public awareness and outreach
programmes are highly recommended. The Chiweta Area requires urgent major
engineering works such as construction of embankments, cable nets, wire
meshes, improving drainage and plugging. Stabilisation and rehabilitation of river
banks is also recommended to minimize bank collapse and flooding. Integration
of traditional knowledge into the existing scientific body knowledge is critical to
a better understanding of the mechanisms that generate landslides
Further work needs to be carried out in areas of willingness to relocate to safer
ground; change in production system; geological analysis of the Chiweta beds; hydro-geological assessment of the areas; development of landslides predictive
models for Malawi; and the development of a landslide early warning system.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-09042008-072002 |
| Date | 04 September 2008 |
| Creators | Msilimba, Golden Gadinala Ashan Chizimba |
| Contributors | Prof PJ Holmes |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-09042008-072002/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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