The Ribb River is one of the components of the Blue Nile River system located in the North Western part of Ethiopia. It drains to Lake Tana, the source of the Blue Nile River. The Ribb has a length of 130 km, with a catchment area of 1,812 km2. The average yearly rainfall of the catchment is 1300 mm, with 80 % occurring between the months of June and September. The average and daily maximum discharge of the river are 15 m3/s and 220 m3/s, respectively. A large dam and a diversion weir 30 km downstream of the dam are under construction to irrigate 15,000 ha of Fogera flood plain (WWDSE and TAHAL, 2007). Downstream of the dam location, the Ribb is a meandering river with slope ranging from 0.18% to 0.03%. The river bed material is dominated by sand with a gravel component in its upper reaches. Intensive agriculture without any natural resources conservation, deforestation, dike construction, pump irrigation and sand mining are the most impactful activities in the Ribb watershed (Tarekegn et al., 2010; Garede and Minale, 2014). The Lake Tana level is regulated since 1995 for hydropower production, which enhances flooding along the lower river reach. During the 2006 event, 45 people died, 30,000 persons were displaced and 5371 ha of agricultural land were inundated (ENTRO, 2010). To prevent flooding, dikes have been constructed in the lower reach of the river. This study aims to describe current river morphodynamic trends, including planimetric changes for the definition of the pre-dam conditions of the river. The first part of the work is presented here with some preliminary results, focusing on the river planimetric changes. This paper describes the initial state of the study.
|Publication status||Published - 2017|
|Event||NCR-Days 2017 - Wageningen, Netherlands|
Duration: 1 Feb 2017 → 3 Feb 2017
|Period||1/02/17 → 3/02/17|
|Other||Netherlands Centre for River Studies is a corporation of the Universities of Delft, Utrecht, Nijmegen, Twente and Wageningen, UNESCO-IHE, RWS-WVL and Deltares|