Now resistance in steep mountain streams

摘要

Resistance to flow at low to moderate stream discharge was examined in five small (1277 km(2) drainage area) tributaries of Chilliwack River, British Columbia, more than half of which exhibit planar lied 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 43 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 now in these conditions is high, highly variable and strongly dependent on stage. The Darcy-Weisbach resistance factor (ff) varies over six orders or magnitude (0-29-12 700) and Manning's n varies over three orders of magnitude (0.047-7.95.). Despite this extreme range, hot[) power equations at. the individual cross sections and Keulegan equations for reach-averaged values describe the hydraulic relations well. Roughness is divided into grain all([ form (considered as all non-grain sources) components. Form roughness is the dominant component, accounting for about 90% of the total rougliness of the system (i.e., form roughness is on average 8.6 times as great as grain roughness). Of the various quantitative and qualitative form-roughness indicators observed, only the sorting coefficient (sigma=D-84/D-50) correlates well with form roughness. Copyright (C) 2008 John Wiley & Sons, Ltd.