Sub-environments of Deposition and Facies Characteristics of the Nyaba River in Enugu Metropolis Southeastern Nigeria

A field study undertaken on the various sub- environments of deposition and sedimentary facies attributes of the Nyaba River in Enugu Metropolis was for a better understanding and interpretation of modern river processes and their sedimentary facies characteristics. A unique attribute of this river is its meandering characteristics at the upper reaches and minor braiding at its lower reaches. The Meandering river sub- environments and their facies are distinguished into the main meander channels/lag deposits, well -developed point bar deposits, the levees and the flood plain deposits. Abandoned channel deposits (meander cut off) is also a common characteristic of the river. Braided channel and longitudinal braid bars constitute the depositional sites of the braided river. Clasts are dominated by sandy fractions with sub-angular to sub-rounded grains. Sorting varies from poorly sorted to well sorted. Pebbles and muddy fractions also occur. Sedimentary structures consist of cross beddings on point bar sands, horizontal laminations, small current ripples, mudcracks and burrows of terrestrial organisms. Nyaba River is classified as a mixed load river.