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| dc.contributor.author | Abate, Mengiste PHD | |
| dc.date.accessioned | 2020-03-19T10:21:50Z | |
| dc.date.available | 2020-03-19T10:21:50Z | |
| dc.date.issued | 2020-03-19 | |
| dc.identifier.uri | http://hdl.handle.net/123456789/10729 | |
| dc.description.abstract | The physical, biological and societal systems are interrelated each other. The societal system over the other systems have brought complex changes. The increasing population density that leads to human-induced land use change, alter fluxes of water and sediment and in turn produces complex landscape changes in physical structure, hydraulics and hydro-geomorphology of river systems. The landscape of upper Blue Nile Basin has been changed due to anthropogenic effects and climate change. Few studies in the upper Blue Nile basin have detailed the response of the rivers to these effects. However, in the international literature this topic has been well addressed and can be applied to Ethiopia in order to understand the past, the present channel dynamics and predicting future channel changes. The objective of this study was to investigate and analyze the response of rivers in Ethiopia to sedimentation, erosion and change of flow regime. We choose the Tana sub-basin because previous data was available. Specifically, this study quantifies the hydro-geomorphology of the 38 km of Gumara River starting from the confluence with Kizin River to Lake Tana using historical images, historical river cross sections, hydrologic, hydraulic, and geotechnical data. In addition, field observations and information obtained from the local people and existing structures were used as data sources. The results show that the changes to Gumara River channel morphology in the alluvial plain is largely controlled by the interplay between discharge regime and sediment loads, which are influenced by human factors and the lake levels. Old maps show that before 1957 when shifting cultivation was practiced the Gumara delta did not expand indicating that the sediment concentrations in the Gumara were small. After 1957 the iv lower reach of Gumara near its mouth underwent major morphological change and delta expanded on average by 5 ha/yr and increase in height by 3 cm/yr. After 1957 the Gumara River although the planform changes are very slow, the bed has aggregated greatly with in-channel deposition (3 m in 46 years). When the ratio of curvature radius to channel width is 3.5, the Gumara River at its bends is experiencing a maximum bank retreat of 1.95 m/yr and the nearby land is lost on average by 0.075 ha/km/yr. The raise of the river bed level amplifies the flashy nature of the river, and results in more frequent high floods and sediment concentrations. This will further increase the river bed level and in turn reduces the flood carrying capacity of the channel. This dissertation shows that human factors are the major driver for the increasing sediment loads in the changes that occur in Gumara River. Thus, restoration of rivers in the Fogera Plain to decrease flooding should include effective catchment-based management practices to offset the negative aspects of the increasing population density in the uplands. | en_US |
| dc.language.iso | en | en_US |
| dc.subject | Hydraulic and Water Resources Engineering | en_US |
| dc.title | Human impact on Hydro-geomorphology of Gumara River upper Blue Nile basin, Ethiopia | en_US |
