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River delta eco-morphodynamics under changing scenarios. The case of Lake Turkana, Kenya
  • Simone Zen,
  • Paolo Perona,
  • Encarni Medina-Lopez
Simone Zen
The University of Edinburgh
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Paolo Perona
École polytechnique fédérale de Lausanne ‐ EPFL
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Encarni Medina-Lopez
The University of Edinburgh

Corresponding Author:[email protected]

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In this work we explore the impact that changes in local climate and river hydrology have on the morphodynamics 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. To quantify changes in land use and river morphology and relate these to river hydrology we collect a historical dataset by combining information from different satellite sources. We observed that the amount of bare sediments progressively diminished and the biomass became more dense compared to the existence of sparse biomass in the past. We argue that this is due to the new river hydrology and sediment load imposed by the dam, which increased sediment erosion by deepening the channel. The dam also increased the low flow and reduced peak during flood season reducing the natural oscillations of the water table and the possibility to plant was removed during floods. We also indicate that the new hydrology and reduced sediments have changed, respectively, the downstream (e.g. lake level), and upstream (e.g. mouth bar deposition) boundary conditions controlling the evolution of the delta structure. As a result, the delta morphology became less dynamic and less complex.