Morphodynamic Trends of the Ribb River, Ethiopia, Prior to Dam Construction
Tóm tắt
The meandering Ribb River flows in northwest Ethiopia to Lake Tana, the source of the Blue Nile River. The river has already undergone changes due to several human interventions, such as embanking, sand mining, water extraction and lake level regulation for hydropower. At present, a dam and a weir are under construction to store and divert water for irrigation. This will strongly alter both water and sediment discharges to the downstream river reaches, causing adjustments to the morphology. Assessing the current morphodynamic trends is the first necessary step to study the future effects and find ways to mitigate them. This paper presents an analysis of the current and past river based on newly collected data, aerial photographs, SPOT and Google Earth images. The riverbed changes are derived from historical staff gauge height analysis. The effects of sediment mining and water extraction are assessed using the theory of morphodynamic equilibrium. The findings of the analysis show a reduction of sediment transport capacity in the downstream direction, which has resulted in intense sediment deposition, resulting in blockage of the Lower River reach and subsequent channel avulsion. The effects of Lake Tana level regulation on the observed processes appear to be minor.
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Tài liệu tham khảo
Jansen, P.P., Van Bendegom, L., De Varies, M., and Zenen, A. (1979). Principles of River Engineering. The Non-Tidal Alluvial River, Delftse Uitgevers Maatschappij B.V.
Latapie, 2014, Assessing channel response of a long river influenced by human disturbance, Catena, 121, 1, 10.1016/j.catena.2014.04.017
Gilvear, 1999, Fluvial geomorphology and river engineering: Future roles utilizing a fluvial hydrosystems framework, Geomorphology, 31, 229, 10.1016/S0169-555X(99)00086-0
Bravard, J., Kondolf, G., and Piégay, H. (1999). Environmental and Societal Effects of Channel Incision and Remedial Strategies. Incised River Channels: Processes, Forms, Engineering and Management, Wiley.
Gilvear, 1993, River management and conservation issues on formerly braided river systems; the case of the River Tay, Scotland, Geol. Soc. Lond. Spec. Publ., 75, 231, 10.1144/GSL.SP.1993.075.01.14
Marston, 1995, Channel metamorphosis, floodplain disturbance, and vegetation development: Ain River, France, Geomorphology, 13, 121, 10.1016/0169-555X(95)00066-E
Gilvear, 1992, Channel change and flood events since 1783 on the regulated River Tay, Scotland: Implications for flood hazard management, Regul. Rivers Res. Manag., 7, 247, 10.1002/rrr.3450070304
Nelson, 2016, The international river interface cooperative: Public domain flow and morphodynamics software for education and applications, Adv. Water Resour., 93, 62, 10.1016/j.advwatres.2015.09.017
Belete, M.A. (2013). Modeling and Analysis of Lake Tana Sub-Basin Water Resources Systems, Ethiopia. [Ph.D. Thesis, University of Rostock].
WWDSE, and TAHAL (2007). Ribb Dam Hydrological Study (Final Report), Water Works Design and Supervision Enterprise (WWDSE) and TAHAL Consulting Engineers Ltd.
Brandt, 2000, Classification of geomorphological effects downstream of dams, Catena, 40, 375, 10.1016/S0341-8162(00)00093-X
Graf, 2006, Downstream hydrologic and geomorphic effects of large dams on American Rivers, Geomorphology, 79, 336, 10.1016/j.geomorph.2006.06.022
Williams, G.P., and Wolman, M.G. (1984). Downstream Effects of Dams on Alluvial Rivers, U.S. Government Printing Office.
Kondolf, G.M. (1997). Hungry water—Effects of dams and gravel mining on river channels and floodplains. Aggreg. Resour. Glob. Perspect. AA Balkema Vermont, 113–129.
Khan, 2014, Effects of dam operation on downstream river morphology: The case of the Middle Zambezi River, Proc. Inst. Civ. Eng. Water Manag., 167, 585, 10.1680/wama.13.00122
De Vries, M. (August, January 27). A morphological time scale for rivers. Proceedings of the 16th Congress IAHR, São Paulo, Brazil.
Tekleab, 2013, Hydro-climatic trends in the Abay/Upper Blue Nile Basin, Ethiopia, Phys. Chem. Earth Parts A/B/C, 61, 32, 10.1016/j.pce.2013.04.017
Abate, 2015, Morphological changes of Gumara River channel over 50 years, Upper Blue Nile Basin, Ethiopia, J. Hydrol., 525, 152, 10.1016/j.jhydrol.2015.03.044
Tesemma, 2010, Trends in rainfall and runoff in the Blue Nile Basin: 1964–2003, Hydrol. Process., 24, 3747, 10.1002/hyp.7893
Hurni, 2005, The implications of changes in population, land use, and land management for surface runoff in the Upper Nile Basin area of Ethiopia, Mt. Res. Dev., 25, 147, 10.1659/0276-4741(2005)025[0147:TIOCIP]2.0.CO;2
Dessie, 2014, Effects of the floodplain on river discharge into Lake Tana (Ethiopia), J. Hydrol., 519, 699, 10.1016/j.jhydrol.2014.08.007
BRLi, and MCE (2010). Pump, Drainage Schemes at Megech: Environmental and Social Impact Assessment of the Ribb Irrigation and Drainage Project, MCE.
SMEC (2008). Hydrological Study of the Tana-Beles Sub-basin: Main Report, Snowy Mountains Engineering Corporation (SMEC) International Pty Ltd.
Kinzel, P., and Runge, J. (2010). Summary of Bed-Sediment Measurements Along the Platte River, Nebraska, 1931–2009, U.S. Geological Survey.
ENTRO (2010). Flood Risk Mapping Consultancy for Pilot Areas in Ethiopia, ENTRO. Final Report to the Eastern Nile Technical Regional Office (ENTRO).
Snowy Mountains Engineering Corporation (SMEC) (2008). Hydrological Study of the Tana-Beles Sub-Basin: Surface Water Investigation, SMEC International Pty Ltd.
Abate, 2017, Long-term landscape changes in the Lake Tana Basin as evidenced by delta development and floodplain aggradation in Ethiopia, Land Degrad. Dev., 28, 1820, 10.1002/ldr.2648
Parker, G., Wilcock, P.R., Paola, C., Dietrich, W.E., and Pitlick, J. (2007). Physical basis for quasi-universal relations describing bankfull hydraulic geometry of single-thread gravel bed rivers. J. Geophys. Res. Earth Surf., 112.
Wilkerson, 2010, Physical basis for quasi-universal relationships describing bankfull hydraulic geometry of sand-bed rivers, J. Hydraul. Eng., 137, 739, 10.1061/(ASCE)HY.1943-7900.0000352
Leopold, L.B., and Wolman, M.G. (1957). River Channel Pattern: Braided, Meandering and Straight, U.S. Government Printing Office.
1995, Prediction of alluvial channel pattern of perennial rivers, Geomorphology, 12, 259, 10.1016/0169-555X(95)00014-V
Crosato, A. (2008). Analysis and Modelling of River Meandering. [Ph.D. Thesis, Delft University of Technology, Nieuwe Hemweg 6b].
Blom, 2017, The equilibrium alluvial river under variable flow and its channel-forming discharge, J. Geophys. Res. Earth Surf., 122, 1924, 10.1002/2017JF004213
Leopold, L.B., Wolman, M.G., and Miller, J.P. (1964). Fluvial Processes in Geomorphology, W.H. Freeman and Company.
Williams, 1978, Bank-full discharge of rivers, Water Resour. Res., 14, 1141, 10.1029/WR014i006p01141
Vargas-Luna, A., Crosato, A., Byishimo, P., and Uijttewaal, W.S. (2018). Impact of flow variability and sediment characteristics on channel width evolution in laboratory streams. J. Hydraul. Res., 1–11.
Shaw, E.M. (2002). Hydrology in Practice, Stanley Thornes Pub.. [3rd ed.].
Meyer-Peter, E., and Müller, R. (1948, January 7–9). Formulas for Bed-Load Transport. Proceedings of the International Association for Hydraulic Research (IAHR) 2nd Meeting, Stockholm, Sweden.
Wong, 2006, Reanalysis and correction of bed-load relation of Meyer-Peter and Müller using their own database, J. Hydraul. Eng., 132, 1159, 10.1061/(ASCE)0733-9429(2006)132:11(1159)
Engelund, F., and Hansen, E. (1967). A Monograph on Sediment Transport in Alluvial Streams, TEKNISKFORLAG Skelbrekgade.
Crosato, 2016, Numerical study on river bar response to spatial variations of channel width, Adv. Water Resour., 93, 21, 10.1016/j.advwatres.2015.10.003
Frings, R.M., Schüttrumpf, H., and Vollmer, S. (2011). Verification of porosity predictors for fluvial sand-gravel deposits. Water Resour. Res., 47.
Garede, 2014, Land use/cover dynamics in Ribb watershed, North Western Ethiopia, J. Nat. Sci. Res., 4, 9
Frings, R.M. (2015). Sand and gravel on the move: Human impacts on bed-material load along the Lower Rhine River. Geomorphic Approaches to Integrated Floodplain Management of Lowland Fluvial Systems in North America and Europe, Springer.
Thornton, 2006, Sand mining impacts on long-term dune erosion in Southern Monterey Bay, Mar. Geol., 229, 45, 10.1016/j.margeo.2006.02.005
Jiang, 2013, Combined impacts of sand mining activities: The Nandu River downstream segment, Adv. Mater. Res., 671–674, 3134, 10.4028/www.scientific.net/AMR.671-674.3134
Surian, 1999, Channel changes due to river regulation: The case of the Piave River, Italy, Earth Surf. Process. Landf., 24, 1135, 10.1002/(SICI)1096-9837(199911)24:12<1135::AID-ESP40>3.0.CO;2-F