References

NHESSD

Natural Hazards and Earth System Sciences Discussions

NHESSD

Nat. Hazards Earth Syst. Sci. Discuss.

2195-9269

Göttingen, Germany

10.5194/nhessd-2-5171-2014

Floods in the Niger basin – analysis and attribution

Aich

https://orcid.org/0000-0002-3699-3775

¹ Koné

² Hattermann

F. F.

¹ Müller

E. N.

Potsdam Institute for Climate Impact Research, Potsdam, Germany

Wetlands International, Mali Office, Mopti, Mali

Institute of Earth and Environmental Science, University of Potsdam, Potsdam, Germany

14 08 2014

2 8 5171 5212

2014

This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/

This article is available from https://nhess.copernicus.org/preprints/2/5171/2014/nhessd-2-5171-2014.html

The full text article is available as a PDF file from https://nhess.copernicus.org/preprints/2/5171/2014/nhessd-2-5171-2014.pdf

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.

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