Model-based study of the role of rainfall and land use–land cover in the changes in the occurrence and intensity of Niger red floods in Niamey between 1953 and 2012
Since 1950, the Niger River basin has gone through three main climatic periods: a wet period (1950–1960), an extended drought (1970–1980) and since 1990 a recent partial recovery of annual rainfall. Hydrological changes co-occur with these rainfall fluctuations. In most of the basin, the rainfall de...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-07-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | http://www.hydrol-earth-syst-sci.net/20/2841/2016/hess-20-2841-2016.pdf |
| Summary: | Since 1950, the Niger River
basin has gone through three main climatic periods: a wet period
(1950–1960), an extended drought (1970–1980) and since 1990
a recent partial recovery of
annual rainfall. Hydrological changes co-occur with these rainfall
fluctuations. In most of the basin, the rainfall deficit caused an enhanced
discharge deficit, but in the Sahelian region the runoff increased despite
the rainfall deficit. Since 2000 the Sahelian part of the Niger has been hit
by an increase of flood hazards during the so-called red flood period. In
Niamey city, the highest river levels and the longest flooded period ever
recorded occurred in 2003, 2010, 2012 and 2013, with heavy casualties and
property damage. The reasons for these changes, and the relative role of
climate versus land use–land cover (LULC) changes are still debated and are
investigated in this paper. The evolution of the Niger red flood in Niamey
from 1950 to 2012 is analysed based on long-term records of rainfall (three
data sets based on in situ and/or satellite data) and discharge, and a
hydrological model. The model is first run with the present LULC conditions
in order to analyse solely the effect of rainfall variability. The impact of
LULC and drainage area modification is investigated in a second step. The
simulations based on the current surface conditions are able to reproduce the
observed trend in the red flood occurrence and intensity since the 1980s.
This has been verified with three independent rainfall data sets and implies
that rainfall variability is the main driver for the red flood
intensification observed over the last 30 years. The simulation results since
1953 have revealed that LULC and drainage area changes need to be invoked to
explain the changes over a 60-year period. |
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| ISSN: | 1027-5606 1607-7938 |