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  4. River delta eco-morphodynamics under changing scenarios: The case of Lake Turkana, Kenya
 
research article

River delta eco-morphodynamics under changing scenarios: The case of Lake Turkana, Kenya

Zen, Simone
•
Perona, Paolo  
•
Medina-Lopez, Encarni
March 10, 2023
Geomorphology

In this work we explore the impact that changes in local climate and river hydrology have on the morphody-namics of a river delta, particularly focusing on the evolution of the delta generating at the lake inlet. We investigated the case of the delta in the lower reach of the Omo River in Ethiopia, which flows into lake Turkana, Kenya. The lake is the fourth largest lake and the largest desert lake in the world. This case study is of particular interest because within the last decades three dams have been built within the Omo basin. Among these, the Gibe III dam had a huge impact on the river hydrology and the sediment supply. To quantify changes in land use and river morphology and relate these to climate change and river hydrology we collated a historical dataset by combining information from different satellite sources. We observed that the amount of bare sediments pro-gressively diminished and the biomass became denser compared to the existence of sparse biomass in the past. We argue that this is due to the changes in river hydrology and sediment load imposed by the dam, which increased sediment erosion by deepening the channel. The presence of the dam also increased the low flow level and reduced the peak flow during flood season, reducing the natural oscillations of the water table. In conse-quence, the possibility to plant for the local population was removed during floods. Our findings also indicate that the hydrology and reduced sediment discharge have changed the downstream (e.g. lake level), and upstream (e.g. mouth bar deposition) boundary conditions controlling the evolution of the delta structure, respectively. As a result, the delta morphology became less dynamic and less complex.

  • Details
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Type
research article
DOI
10.1016/j.geomorph.2023.108640
Web of Science ID

WOS:000955178000001

Author(s)
Zen, Simone
Perona, Paolo  
Medina-Lopez, Encarni
Date Issued

2023-03-10

Published in
Geomorphology
Volume

428

Article Number

108640

Subjects

Geography, Physical

•

Geosciences, Multidisciplinary

•

Physical Geography

•

Geology

•

omo river

•

lake turkana

•

gilgel gibe dams

•

river delta eco-morphodynamics

•

vegetation

•

dynamics

•

flow

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
PL-LCH  
Available on Infoscience
April 24, 2023
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/197052
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