Régimes des flux des matières solides en suspension au Cameroun: revue et synthèse à l’échelle des principaux écosystèmes; diversité climatique et actions anthropiques / Regimes of suspended sediment flux in Cameroon: review and synthesis for the main ecosystems; climatic diversity and anthropogenic activities

Present-day sediment dynamics of the Sanaga catchment (Cameroon): from the total suspended sediment (TSS) to erosion balance

“…Figure 3 shows how the suspended sediment concentrations respond to changes in discharge at the monthly time frame for the three years (1995/97 and 2005/06) of detailed measurements. It can be noted that the TSS concentration/ monthly discharge relationships remain identical from one year to the other, forming clockwise hysteresis loops, as has been revealed in many earlier studies , Olivry et al 1988, Picouet et al 2002, Liénou et al 2005. They thus may be characteristic of tropical rivers with a unimodal flow regime for which the TSS dynamics reveal three main stages of mechanical denudation: the stage of initial erosion, the stage of attenuated or late erosion and the stage of sediment deposition (Gac 1986, Kattan et al 1987, Olivry et al 1989, Boeglin and Probst 1996.…”

“…The different water samples were collected at 30-50 cm below the water surface, at the same place on the river, and preferentially where the flow velocity was high enough to allow for a good homogenization of the solid particles of different sizes. In fact, for the large streams of the tropical zone of Africa, including those of Cameroon, the technique of sampling along one vertical, which is rather simple, fast and practical, gives results that are satisfactory and relatively close to those of the full solid gauging method (Nouvelot 1972a, 1972b, Olivry et al 1988, Sigha-Nkamdjou et al 1998, Liénou et al 2005.…”

“…Later on, investigations were made on small to medium size drainage basins in this region with the following objectives: first, to understand the effects of the variations in spatial scale in relation to tectonic history, vegetation and lithology (Sigha-Nkamdjou 1994, Bird et al 1994, Ndam Ngoupayou 1997, Giresse and Maley 1998, Olivie-Lauquet et al 2000, Braun et al 2005; second, to evaluate the impact of environmental change of climatic and anthropogenic origin (Sighomnou 2004, Sigha-Nkamdjou et al 2005, Liénou et al 2005, Sighomnou et al 2007. Regarding the latter, no widespread study has been done on the Sanaga catchment despite the fact that it provides about 90% of the hydroelectric energy of Cameroon.…”

GCM-related uncertainty for river flows and inundation under climate change: the Inner Niger Delta

“…Widespread declines in vegetation cover have been reported for the Sahelian region (e.g. Diello et al 2005, Liénou et al 2005, Leblanc et al 2008. Such changes could not be included in the model given its empirically established calibration parameters.…”

Denudation rates on cratonic landscapes: comparison between suspended and dissolved fluxes, and 10Be analysis in the Nyong and Sanaga River basins, south Cameroon

“…In fact, for the large streams of the tropical zone of Africa, including those of Cameroon, the sampling technique along one vertical which is rather simple, fast and practical, gives results that are satisfactory and relatively close to those of the full solid gauging method (e.g. Olivry et al , ; Lienou et al , ; Ndam Ngoupayou et al , )…”