Floods in the Niger basin – analysis and attribution
V. Aich1, B. Koné2, F. F. Hattermann1, and E. N. Müller31Potsdam Institute for Climate Impact Research, Potsdam, Germany 2Wetlands International, Mali Office, Mopti, Mali 3Institute of Earth and Environmental Science, University of Potsdam, Potsdam, Germany
Received: 08 Jul 2014 – Accepted for review: 24 Jul 2014 – Discussion started: 14 Aug 2014
Abstract. This study addresses the increasing flood risk in the Niger basin and assesses the damages that arise from flooding. Statistics from three different sources (EM-DAT, Darthmouth Flood Observatory, NatCat Munich RE) on people affected by floods show positive trends for the entire basin beginning in the 1980s. An assessment of four subregions across the Niger basin indicates even exponential trends for the Sahelian and Sudanian regions. These positive trends for flooding damage match up to a time series of annual maximum discharge (AMAX): the strongest trends in AMAX are detected in the Sahelian and Sudanian regions, where the population is also increasing the fastest and vulnerability generally appears to be very high. The joint effect of these three factors can possibly explain the exponential increase in people affected by floods in these subregions. In a second step, the changes in AMAX are attributed to changes in precipitation and land use via a data-based approach within a hypothesis-testing framework. Analysis of rainfall, heavy precipitation and the runoff coefficient shows a coherent picture of a return to wet conditions in the basin, which we identify as the main driver of the increase in AMAX in the Niger basin. The analysis of flashiness (using the Richards–Baker Index) and the focus on the "Sahel Paradox" of the Sahelian region reveal an additional influence of land-use change, but it seems minor compared to the increase in precipitation.
Aich, V., Koné, B., Hattermann, F. F., and Müller, E. N.: Floods in the Niger basin – analysis and attribution, Nat. Hazards Earth Syst. Sci. Discuss., 2, 5171-5212, doi:10.5194/nhessd-2-5171-2014, 2014.