considered free from impact caused by floods or landslides, other 
threats from Mount Cameroon eruption, particularly lava flows, 
threaten the population. (Krimsky, 1992). The need for effective 
decision making towards risk reduction in this region has 
necessitated this study, to investigate the environmental and 
socio-economic impact and possibilities of the emplacement of 
effective monitoring/early warning systems in the event of the 
collapse of the dam. This will enable decision makers and 
planners to understand areas to concentrate their concerted 
efforts with a view to developing mitigation measures to reduce 
the level of risk and to guarantee the lives of the population in 
this region. 
2.1 Brief Description of Lake Nyos 
Lake Nyos occupies a major crater formed through a hydro- 
volcanic eruption about 400 years ago. The lake is located on the 
Oku volcanic line in Northwestern region of Cameroun. It has an 
estimated length of 1.8 to 2.0 km and width of 1.2 km with a 
depth of about 208 meters. At the lowest point, the walls 
measures 40 meters high and 45 meters wide. According to 
Freeth and Kay (1987), there is a magma chamber beneath the 
region of the lake. This chamber holds a large volume of carbon 
dioxide which seeps through the charging waters of Lake Nyos 
with an estimated 90 million kilograms of carbon dioxide 
annually. The lake contains about 55 million cubic litres of 
oxidized waters. Overtime, the waters have become super 
saturated, and in an event such as earthquake or volcanic 
eruption, large amounts of CO2 may suddenly erupt. Most of the 
times, however, the lake is stable and carbon dioxide remains in 
solution in the lower layers. 
In most crater lakes, turnover of the stratified waters occurs 
periodically and formless amounts of dissolved gases are 
released. However, the problem with lake Nyos is that the lake 
does not periodically turn over. Thus dissolved gases are allowed 
  
Figure 1: Location of the Lake Nyos region 
to reach much higher concentrations. The lake is also thermally 
stratified, with layers of warm, less dense water near the surface 
floating on the colder, dense water layers near the lake bottom. 
Over long periods, carbon dioxide gas seeping into the cold 
waters at the bottom of the lake is dissolved in great amounts 
(Tazieff, 1989). In the event of any agitation and the collapse of 
the lake dam, a large volume of CO2-rich water may flow down 
the associated drainage basins with the consequence of a 
devastating flood on the adjoining settlements. This development 
may portend great danger for the region around the lake, the 
resources and settlements/population downstream of rivers that 
take their source from Lake Nyos water, such as the Katsina-ala 
river that flows North-West of the area into Nigeria. 
3.0 SCOPE AND METHODS OF STUDY 
The study area covers 14 Local Government Areas (LGAs), 
which could be flooded through the collapse of lake Nyos dam 
and release of a large volume of carbonated water, because of 
their proximity to the flood plains of Katsina-Ala river and other 
adjoining river basins. The area is situated between latitudes 50 
25 minutes and 80 8 minutes and longitudes 70 47 minutes and 
100 45 minutes (Figure 1). All the LGAs are located in Benue 
state. If it occurs, the disaster could have some ripple effects in 
terms of panic, tension and resettlement of the displaced persons 
that may transend the boundaries of these local governments. 
The potential devastating effect may include the socio-economic 
and health status of the communities in the Katsina-Ala and 
Benue river basins who are mostly farmers and fishermen with 
intensive activities at the riverine areas.(Blaike, 1994). 
Reconnaissance survey and field observations, including field 
measurements, administration of questionnaire and hydrological 
modeling, were used to investigate the potential environmental 
and socio-economic impact; these also include the possibilities of 
the emplacement of effective monitoring/early warning systems 
for flood disaster prediction and control in an event of the 
collapse of the dam. 
  
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