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| dc.contributor.author | Alelegne, Ammar | |
| dc.date.accessioned | 2020-03-19T07:51:44Z | |
| dc.date.available | 2020-03-19T07:51:44Z | |
| dc.date.issued | 2020-03-19 | |
| dc.identifier.uri | http://hdl.handle.net/123456789/10684 | |
| dc.description.abstract | Ribb River is one of major Tributary River to Lake Tana which is part of upper Blue Nile basin. The River has experience a significant planform alteration over the past 30 years. This can be observed south to north ward lateral migration of Ribb Stream path from the boundaries between adjacent (Libokemkem & Fogera) Woredas to the present day River planform that is entirely become a part of Libokemkem Woreda in the lower reach. However, the causes for shifting such Ribb River course are not studied. This research was conducted to examine the Ribb River planform changes occurred in the last 30 years using SPOT and LandSat images. Land use, DEM-90, Soil type, rainfall, flow and sediment concentration have also used. The problem was addressed by employing methods of Remote Sensing Image analysis and Digitizing techniques integrated with Terrain analysis based indices. The annual volume of precipitation value shows almost uniform rainfall pattern in the area. On the other hand, average monthly flow rate indicates a decreasing trend. The sediment concentration shows a direct relation with the stream flow rate. As image analysis results confirm that the Ribb River has under gone a planform changes. Its sinuosity index values (1.82 to 1.94) indicate the meandering nature of Ribb Rivers. At the lower reach the river course is totally changed to new location. And the new river path is shifted to the north laterally by 6,220 m. Similarly, in the upper reach a maximum water course shift of 26 m and 70 m has occurred. The change in planform is high in the lower reach. There is also about 0.97 ha delta formed at recent mouth of Ribb River joining to Lake Tana, whereas at the previous river mouth a delta of about 89.74 ha in 1985, 46.30 ha in 2000 and 5.65 ha in 2015 was emerged. This implies that there is diminishing in delta size from 2.6 ha to 2.9 ha annually. Planform alteration of Ribb River at different reach is driven by sediment deposition, cutoff construction and bar formation. Generally, to better understand the Ribb River morphology the future researchers shall gain adequate data of ground survey, high resolution images, past aerial photographs, hydrological and meteorological data sets | en_US |
| dc.language.iso | en | en_US |
| dc.subject | Hydraulic engineering | en_US |
| dc.title | Ribb River Planform Changes Over 30 Years; Upper Blue Nile Basin, Ethiopia | en_US |
| dc.type | Thesis | en_US |
