Slope and roughness variation in small meandering alluvial stream channels

This thesis examines slope, resistance, and other hydrologic components in particular channel bed environments. The primary objective of this research is to document the form, magnitude, and variance of certain within-channel hydraulic properties during discharge increases. The analysis examines the stage-slope-roughness interdependency; evaluates existing theoretical and empirical hydrologic relationships in natural settings; and quantifies the values and variances of roughness and slope.;Geologic controls dominate roughness variation as the effect of local geology on both slope and channel bed particle size largely determines flow resistance within a particular cross-section. Roughness generally decreases with stage at-a-station in all the cross-sections investigated. A rapid decrease from markedly high values typical of low flow, to a general decrease in roughness towards bankfull discharges typified the sequence of roughness decrease in the gravel bed river although Manning roughness coefficients are still relatively high (0.035-0.055) at bankfull discharges. Because of the relatively fine texture of the sand bed channel (mean = 0.38 mm), a plane bed with associated low roughness values (0.011-0.016) occurs at sub-bankfull discharges. Subsequent stage increases to bankfull generally results in moderate increases in channel roughness. The mixed load channel corresponds with low roughness values at both low flow (0.030-0.035) and bankfull discharges (0.02-0.025).;The analysis demonstrates the critical role of slope in estimating roughness. The energy grade line was calculated for a range of discharges and compared to several slope proxies. For flows contained within the channel, bankfull water surface slope corresponds to within 10% of the energy grade line. If bankfull water surface slopes are not available, low flow water surface slopes represent a better estimator of energy grade line than either topographic map slope or channel bed slope. For large magnitude floods, the correlation between water surface and topographic map slope ranges from 7% to 78%. The strongest association occurs during rainstorms distributed fairly uniformly throughout a basin, and when floods attain sufficient stage to minimize resistance effects of floodplain features. Energy gradients of these large magnitude floods are generally overpredicted by water surface slope (mean = 44%) and topographic map slope (mean = 71%).