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Abstract: The purpose of this study is to evaluate a slope threshold for bar formation, and to qualitatively analyze empirical relationships among variables which affect bar occurrence and morphology for 15 gravel bed stream reaches in northwestern California. Channel bar formation depends mainly on slope, particle size, and width to depth ratio. A model for the slope threshold above which no bars are present is contrasted with the field data for this study. Church and Jones' (1982) model based on the relation of flow depth to particle size determines the maximum slope allowable for bar formation. The slope threshold ranges between 0.025 and 0.08 when Shields' (1936) value of t*=0~05 is used. When Parker and Klingeman's (1982) value t*=0.017 (for D90 ) is used, the slope threshold ranges from 0.003 to 0.01, and when their value t*=0.035 for D50 Is used, the slope threshold ranges between 0.017 and 0.058. Based on field data for nothwestern California coastal streams, no riffles or storage bars are present at slopes above 0.02 in reaches without obstacles. At slopes greater than 0.02, step-pool structure is common. Furthermore, bar morphology Is dependent on the relation between slope and bed material size. Storage bars attain a height of 0.71 bankfull depth; riffles attain a height of 0.26 bankfull depth. Bars In the study reaches are present at bankfull width to depth ratios less than predicted by Jaeggi (1982) and Parker (1978). The relationship between flow intensity and the product of channel slope and width to depth ratio, Indicates distinct fields for gravel bar morphology Including: storage bars with riffles, storage bars only, and no bars (with step-pool morphology). Steep north coastal reaches would probably form braid bars If mean particle sizes were smaller or width to depth ratios were larger.