Background: Flood is one of the most destructive natural disasters of climate change effects in West Africa. Flood risk occurrence is a combination of natural and anthropogenic factors, which calls for a better understanding of its spatial extent. The aim of this paper is to identify, and map areas of flood risk in Abidjan district. Results: This work is based on the integration of multi-criteria data including slope, drainage density, type of soil, Isohyet, population density, land use and sewer system density within ArcGIS interface. The resulting AHP flood risk map shows that areas under high and very high flood risk covers 34 % of the study area. Conclusion: The Analytic Hierarchy Process (AHP) method used as a multi-criteria analysis allowed the integration of several elements under two criteria, hazards and vulnerability, for flood risk assessment and mapping. Results revealed that, Abidjan district is heavily exposed to the risk of flooding. Eight out of thirteen (8/13) municipalities within the district are at a high risk of flooding which calls for decision makers to effectively develop strategies for future flood occurrences within the Abidjan district (South of Côte d'Ivoire).

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[1] Savannas cover large areas of the Earth's surface and play an important role in global carbon cycling. West Africa is dominated by a variety of savanna ecosystems; however, they have been poorly studied up to now. In the present study, energy and carbon dioxide exchange was measured over a 2-year period using the eddy covariance technique at a southern Sudanian savanna site in Burkina Faso that was not subject to human disturbances except for annual burning. Turbulent energy exchange was dominated by sensible heat flux in the dry season (November-May) and by latent heat flux in the wet season (June-September), with peak values higher than 300 W m À2 and lower than 100 W m À2 for the dominating and the minor component, respectively. The ecosystem was a marginal CO 2 source in the dry season, whereas significant CO 2 uptake was found in the rainy season. CO 2 fluxes showed a clear diurnal pattern, with mean release rates of 0.2 mg CO 2 m À2 s À1 during nighttime and mean maximum uptake rates of 1.0 mg CO 2 m À2 s À1 in July and August around midday. Diurnal courses of CO 2 flux were in phase with photosynthetically active radiation (PAR). Highest CO 2 uptake rates of more than 0.8 mg CO 2 m À2 s À1 occurred at PAR levels in excess of 1000 mmol m À2 s À1 . Total net ecosystem CO 2 uptake was 179 ± 98 g C m À2 in the first year and 429 ± 100 g C m À2in the second year of investigation, including an estimate of annual fire C loss of 149 g C m À2 . The remarkable difference in net CO 2 uptake between the two years could be explained by higher rainfall in 2006, revealing the sensitivity of the ecosystem to water availability and rainfall distribution that could lead to a significant change in C sequestration patterns under a changing climate.Citation: Brümmer, C., U. Falk, H. Papen, J. Szarzynski, R. Wassmann, and N. Brüggemann (2008), Diurnal, seasonal, and interannual variation in carbon dioxide and energy exchange in shrub savanna in