In paper is presented investigation results of scour in downstream of weir for different length of bed protection. Investigations were conducted on model taired construction with the over of water above the gate, with stilling pool and horizontal bed protection about lengths 50, 100 and 200 cm. Model was made in geometrical scale 1 : 30. As eroded material in experiments was used sand, d₅₀ = 1,1 mm, (d₈₄/d₁₆)^0,5 = 1,77. Increase length of bed protection in downstream influence on slow down of scouring process, what is due of decrease turbulence intensity of stream below hydraulic jump. For longer bed protection obtained smaller upstream slope of the scour hole and further location place of occurrence maximum depth of scour. Reduction maximum scour depth and the upstream slope of the scour hole minimise the risk of weir failure.

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