Frankl, Amaury

Mullaw, Biadgilgn Demissie

Nyssen, Jan

English

Ghent University Academic Bibliography

Geophysical Research AbstractsVol. 16, EGU2014-14999, 2014EGU General Assembly 2014© Author(s) 2014. CC Attribution 3.0 License.Extreme hydrologic behaviors and their impacts on river morphology inthe semi-endorheic Raya Graben basin (North Ethiopia)Biadgilgn Demissie (1,2), Amaury Frankl (2), and Jan Nyssen (2)(1) Department of Geography and Environmental Studies, Mekelle University, Mekelle, Ethiopia, (2) Ghent University,Department of Geography, Gent, Belgium (biadgilgn.demissie@ugent.be)Due to the occurrence of steep and degraded escarpment slopes and high rain seasonality, the hydrological regimein the Raya Graben (Ethiopia) is characterized by the occurrence of strong flash floods, making the channel mor-phology of the braided rivers very dynamic. In this study, the impact of the flash floods on channel width wasinvestigated. Peak discharges were measured using crest gauges at calibrated cross-sections (bridges near the es-carpment footslope) in the rainy season (July and August) of 2013. In order to investigate the changes in channelmorphology along the river, 15 monitoring sites were established on the Hara and the Etu Rivers, downstream fromthe hydrological stations. The changes in river channel width after peak flow events were measured after every ma-jor event. A linear regression analysis revealed that the increase in channel width was more important towards theend of the rainy season (R2=0.91, p<0.05 for Hara River and R2=0.93, p<0.05 for Etu River). Per cross-section,there was on average 2.11 m channel width change in Hara River (for 22 flash flood events) and 0.74 m in Etu River(for 13 flash flood events). The change in channel width did not show a significant relationship with distance fromthe escarpment footslope. The more pronounced channel widening towards the end of the rainy season is probablydue to the clear water effect in relation to better vegetation cover on the escarpment that prevents sediment frombeing washed to the river. Because the widening of the channel highly impacts primarily farming activities, moreattention should be given to the impacts of flashy floods on the channel width of dryland braided rivers.

Extreme hydrologic behaviors and their impacts on river morphology in the semi-endorheic Raya Graben basin (North Ethiopia)

https://biblio.ugent.be/publication/4416754/file/4416891.pdf

Extreme hydrologic behaviors and their impacts on river morphology in the semi-endorheic Raya Graben basin (North Ethiopia)

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