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This study aimed at understanding the perceptions of stakeholders on urban water erosion in a dryland city - Windhoek (Namibia) - by interviewing 41 stakeholders using semi-structured questionnaires. Stakeholders' perceptions were analysed by addressing their understanding of water erosion dynamics, their perceptions with regards to the causes and the seriousness of erosion damages, and their attitudes towards the responsibilities of urban erosion prevention and damages. The results indicated that there is less awareness of the process as a phenomenon; instead there is more awareness of erosion damages and the factors contributing to the damages. About 69% of the stakeholders considered erosion damages to be ranging from moderate to very serious. However, there were notable disparities between the private householders and public authority groups. The private householders and local authority sectors pointed fingers at each other as regards responsibility for erosion damage payments and for putting up prevention measures. The reluctance to take responsibility could undermine any effort to minimise erosion in urban areas and create a predicament for areas affected, especially in the informal settlements where land management is not carried out by the local authority and land is not owned by the occupants. [ABSTRACT FROM AUTHOR]

This study analyses the increasing number of catastrophic floods in the Niger River Basin, focusing on the relation between long term hydro-climatic variability and flood risk over the last 40 to 100 years. Time series for three subregions (Guinean, Sahelian, Benue) show a general consistency between the annual maximum discharge (AMAX) and climatic decadal patterns in West Africa regarding both trends and major changepoints. Variance analysis reveals rather stable AMAX distributions except for the Sahelian region, implying that the changes in flood behavior differ within the basin and affect mostly the dry Sahelian region. The timing of the floods within the year has changed only downstream of the Inner Niger Delta due to retention processes. The results of the hydro-climatic analysis generally correspond to the presented damage statistics on people affected by catastrophic floods. The damage statistics shows positive trends for the entire basin since the beginning in the 1980s, with the most extreme increase in the Middle Niger. [ABSTRACT FROM AUTHOR]

This study assesses future flood risk in the Niger River Basin (NRB), for the first time considering the simultaneous effects of both projected climate change and land use changes. For this purpose, an ecohydrological process-based model (SWIM) was set up and validated for past climate and land use dynamics of the entire NRB. Model runs for future flood risks were conducted with an ensemble of 18 climate models, 13 of them dynamically downscaled from the CORDEX Africa project and five statistically downscaled Earth System Models. Two climate and two land use change scenarios were used to cover a broad range of potential developments in the region. Two flood indicators (annual 90th percentile and the 20-year return flood) were used to assess the future flood risk for the Upper, Middle and Lower Niger as well as the Benue. The modeling results generally show increases of flood magnitudes when comparing a scenario period in the near future (2021–2050) with a base period (1976–2005). Land use effects are more uncertain, but trends and relative changes for the different catchments of the NRB seem robust. The dry areas of the Sahelian and Sudanian regions of the basin show a particularly high sensitivity to climatic and land use changes, with an alarming increase of flood magnitudes in parts. A scenario with continuing transformation of natural vegetation into agricultural land and urbanization intensifies the flood risk in all parts of the NRB, while a “regreening” scenario can reduce flood magnitudes to some extent. Yet, land use change effects were smaller when compared to the effects of climate change. In the face of an already existing adaptation deficit to catastrophic flooding in the region, the authors argue for a mix of adaptation and mitigation efforts in order to reduce the flood risk in the NRB. [ABSTRACT FROM AUTHOR]