Resistance to flow at low to moderate stream discharge was examined in five small (12-77 km 2 drainage area) tributaries of Chilliwack River, British Columbia, more than half of which exhibit planar bed morphology. The resulting data set is composed of eight to 12 individual estimates of the total resistance to flow at 61 cross sections located in 13 separate reaches of five tributaries to the main river. This new data set includes 625 individual estimates of resistance to flow at low to moderate river stage. Resistance to flow in these conditions is high, highly variable and strongly dependent on stage. The Darcy-Weisbach resistance factor (ff) varies over six orders of magnitude (0·29-12 700) and Manning's n varies over three orders of magnitude (0·047-7·95). Despite this extreme range, both power equations at the individual cross sections and Keulegan equations for reach-averaged values describe the hydraulic relations well. Roughness is divided into grain and form (considered as all non-grain sources) components. Form roughness is the dominant component, account-ing for about 90% of the total roughness of the system (i.e., form roughness is on average 8.6 times as great as grain roughness). Of the various quantitative and qualitative formroughness indicators observed, only the sorting coefficient (σ σ σ σ σ = = = = = D 84 /D 50 ) correlates well with form roughness.

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