Stream power

About: Stream power is a research topic. Over the lifetime, 1135 publications have been published within this topic receiving 51324 citations.

The form and function of headwater streams based on field and modeling investigations in the southern Appalachian Mountains

Abstract: Headwater streams drain the majority of most landscapes, yet less is known about their morphology and sediment transport processes than for lowland rivers. We have studied headwater channel form, discharge and erosive power in the humid, moderate-relief Valley and Ridge and Blue Ridge provinces of the Appalachian Mountains. Field observations from nine headwater (< < < < 2k m 2 drainage area), mixed bedrock‐alluvial channels in a variety of boundary conditions demonstrate variation with respect to slope-area channel initiation, basic morphology, slope distribution, hydraulic geometry, substrate grain size and role of woody debris. These channels display only some of the typical downstream trends expected of larger, lowland rivers. Variations are controlled mainly by differences in bedrock resistance, from the formation level down to short-wavelength, outcrop-scale variations. Hydrologic modeling on these ungauged channels estimates the recurrence of channel-filling discharge and its ability to erode the channel bed. Two-year recurrence discharge is generally larger and closer to bankfull height in the Valley and Ridge, due to low soil infiltration capacity. Discharge that fills the channel to its surveyed bankfull form is variable, generally exceeding two-year flows at small drainage areas (< < < <0·5 km 2 ) and being exceeded by them at greater drainage areas. This suggests bankfull is not controlled by the same recurrence storm throughout a channel or physiographic region. Stream power and relative competence are also variable. These heterogeneities contrast relations observed in larger streams and illustrate the sensitivity of headwater channels to local knickpoints of resistant bedrock and armoring of channels by influx of coarse debris from hillslopes. The general lack of predictable trends or functional relationships among hydraulic variables and the close coupling of channel form and function with local boundary conditions indicate that headwater streams pose a significant challenge to landscape evolution modeling. Copyright © 2005 John Wiley & Sons, Ltd.

Water erosion processes and dynamic changes of sediment size distribution under the combined effects of rainfall and overland flow.

Abstract: Water erosion is a time-varying processes controlled by both rainfall and overland flow. A better understanding of dynamic changes in the sediment load and size distribution with various erosive forces can help to develop and verify erosion models. Here, a total of 11 laboratory simulation experiments were conducted in a 1 m by 3 m flume with 3 storm rainfall intensities (60, 90, 120 mm h−1) and 2 inflow rates (5, 7.5 L min−1) on a silty clay red soil. Time-series measurements of the quantity and size distribution of eroded materials were made during 50 min rainfall/inflow time. The mean weight diameter of the effective sediment, sediment enrichment ratio, average stream power and rainfall power were measured and calculated. Fine sediment particles were associated with the short-lived initial stage, which was combined with sheet flow erosion and splash erosion, whereas coarse particles were associated with the rill development and rill stable stages, which were dominated by rill erosion and interrill erosion, respectively. The

Suspended sediment and turbidity following road construction and logging in western montana

Abstract: Forest management activities in a second order drainage basin increased suspended sediment yields 7.7 fold in the first year following road construction, and two-fold following logging in the second year. Sediment supply limitations resulted in poor correlations between sediment concentrations with discharge. Sediment transport was strongly hysteretic, with the highest sediment concentrations occurring on the rising limbs of snowmelt hydrographs and individual peaks. In addition to discharge, hydrograph characteristics such as limb, dQ/dt, and the product of dQ/dt and limb aided in explaining variability of observed sediment concentrations. Sediment-turbidity relationships were strongly discharge dependent, reflecting the changing composition of the suspended load with stream power and sediment supplies.

Re-examination of Bagnold's empirical bedload formulae

Abstract: Bagnold developed his formula for bedload transport over several decades, with the final form of the relation given in his 1980 paper. In this formula, bedload transport rate is a function of stream power above some threshold value, depth and grain size. In 1986, he presented a graph which illustrated the strength of his relation. A double-log graph of bedload transport rate, adjusted for depth and grain size, versus excess stream power was shown to collapse along a line having a slope of 1·5. However, Bagnold based his analyses on limited data. In this paper, the formula is re-examined using a large data set in order to define the most consistent empirical representation, and dimensional analysis is performed to seek a rationalization of the formula. Functional analysis is performed for the final version of the equation defined by Bagnold to determine if the slope of 1·5 is preserved and to assess the strength of the relation. Finally, relations between excess stream power and bedload transport are examined for a fixed slope of 1·5 to assess the performance of various depth and grain size adjustment factors. The rational scaling is found to provide the best result. Copyright © 2000 John Wiley & Sons, Ltd.

Effects of sediment load on hydraulics of overland flow on steep slopes.

Abstract: Eroded sediment may have significant effects on the hydraulics of overland flow, but few studies have been performed to quantify these effects on steep slopes. This study investigated the potential effects of sediment load on Reynolds number, Froude number, flow depth, mean velocity, Darcy–Weisbach friction coefficient, shear stress, stream power, and unit stream power of overland flow in a sand-glued hydraulic flume under a wide range of hydraulic conditions and sediment loads. Slope gradients were varied from 8·7 to 34·2%, unit flow rates from 0·66 to 5·26×10−3 m2 s−1, and sediment loads from 0 to 6·95 kg m−1 s−1. Both Reynolds number (Re) and Froude number (Fr) decreased as sediment load increased, implying a decrease in flow turbulence. This inverse relationship should be considered in modeling soil erosion processes. Flow depth increased as sediment load increased with a mean value of 1·227 mm, caused by an increase in volume of sediment-laden flow (contribution 62·4%) and a decrease in mean flow velocity (contribution 37·6%). The mean flow velocity decreased by up to 0·071 m s−1 as sediment load increased. The Darcy–Weisbach friction coefficient (f) increased with sediment load, showing that the total energy consumption increased with sediment load. The effects of sediment load on f depended on flow discharge: as flow discharge increased, the influence of sediment load on f decreased due to increased flow depth and reduced relative roughness. Flow shear stress and stream power increased with sediment load, on average, by 80·5% and 60·2%, respectively; however, unit stream power decreased by an average of 11·1% as sediment load increased. Further studies are needed to extend and apply the insights obtained under these controlled conditions to real-world overland flow conditions. Copyright © 2010 John Wiley & Sons, Ltd.