| Summary: | The movement of water over a bed of sediment results in the entrainment of pal1icles. The finer sediment will be entrained earlier than the larger particles or armour layer. Basic questions regarding armour layers need to be resolved is mechanism am-lour layers and the relevant properties of armour layer can they be predicted. The study focused on observations of shear stress on the condition of passive and active conditions on the formation of armor layer at a constant discharge. Hydraulic laboratorium studies using the main sediment-recirculating flume of plexiglass dimensionless width 0.60 m, length of 10.00 m, a depth of 0.45 m and a channel slope of 1 % to 2,6%. The flume experiments created armoured beds testing 5 sediment mixtures with a composition of 70% gravel. 30% sand, and 4 flow rates constant discharge capacity of 25 l/s, 30 l/s, 40 lis and 45 lis. Running on low flow 3 phases which phase graded, phase equilibrium and phase armour The instruments used between digital currentmeter, point gauge meter, sediment feeder, trap sediment, and surfer software version 8.0. The results are shown armour layer structure changes and changes in surface topography. While the grain size profile armour layer more upright, this condition indicates that the formation of annour layer effect on the stability of the channel.
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