Stream power

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

River incision or diversion in response to bedrock uplift

Abstract: INTRODUCTIONMany researchers have examined the long-term behavior of alluvialrivers (i.e., Schumm et al., 1987; Snow and Slingerland, 1990; Paola et al.,1992). On long time scales, alluvial rivers act as sediment-transport systemsthat broadly deposit sediment over low areas in their basins (i.e.,Tucker andSlingerland, 1996). The behavior of bedrock rivers is less well understood,although most workers agree that bedrock erosion is some function of streampower (Howard and Kerby, 1983; Seidl and Dietrich, 1992; Howard et al.,1994). Accordingly,researchers addressing a river’s response to bedrock up-lift equate incision with relatively high stream power and diversion with rela-tively low stream power (e.g., Burbank et al., 1996). However, these studiesassume that the erosion rate of the bedrock channel across the mountainrange controls the eventual outcome; they have not examined the behavior ofthe alluvial river upstream and downstream of the uplift. We propose to lookat the entire erosional and depositional river system and examine the long-term response of a coupled alluvial-bedrock river system to tectonic uplift.Our motivation is general and aims at a greater understanding offluvial and tectonic interactions, but our model is necessarily both specificand simplified:the tectonic uplift of a bedrock massif into the path of a later-ally unconstrained alluvial river. Such a scenario has two possible out-comes: either the river maintains its original course and incises through theuplift, or the river diverts and forms a new course around the uplift. A sig-nificant complication in the analysis of this scenario is that the evolvingriver system is partial alluvial and partial bedrock channeled. Because thebehaviors of these two river types are different, modeling requires couplingdiverse systems. We construct an analytical model to perform a first-orderanalysis of this coupled system. Our objective is to identify the specific fac-tors that determine the final outcome of river diversion or incision.Our model focuses on long time scales (10

Bed load transport in braided gravel‐bed stream models

Abstract: Bed load transport rate was measured in ten self-formed small-scale gravel braided streams developed in a laboratory flume at several different values of steady discharge and flume gradient. The streams are approximate Froude models of typical prototype braided streams but of no particular river. Slight viscous effects may be present in the models because particle Reynolds numbers are close to 70. Total bed load discharge was measured every fifteen minutes throughout each 60 hour run. In addition, 80 channel cross-sections were measured in each run to establish the average channel geometry. Total bed load transport rate correlates well with total discharge and total stream power, although at a given stream power bed load discharge is greater when braiding is less intense and the width/depth ratio is lower. Analysis using unit stream power and cross-section average bed shear stress reveals that the laboratory data conform to existing empirical bed load transport relationships. However, comparison with field data from gravel-bed rivers shows discrepancies that may be due to differences in bed material size gradation and bed sediment structure. At constant discharge, wide fluctuations in bed load discharge occur with some regularity. Periods range from 2 to 10 hours in the models, which is equivalent to several tens of hours in a prototype. The presence of these long-period fluctuations compounds the problems of field measurement of bed load in braided streams.

Effect of hydraulic parameters on sediment transport capacity in overland flow over erodible beds

Abstract: . Sediment transport is an important component of the soil erosion process, which depends on several hydraulic parameters like unit discharge, mean flow velocity, and slope gradient. In most of the previous studies, the impact of these hydraulic parameters on transport capacity was studied for non-erodible bed conditions. Hence, this study aimed to examine the influence of unit discharge, mean flow velocity and slope gradient on sediment transport capacity for erodible beds and also to investigate the relationship between transport capacity and composite force predictors, i.e. shear stress, stream power, unit stream power and effective stream power. In order to accomplish the objectives, experiments were carried out in a 3.0 m long and 0.5 m wide flume using four well sorted sands (0.230, 0.536, 0.719, 1.022 mm). Unit discharges ranging from 0.07 to 2.07 × 10−3 m2 s−1 were simulated inside the flume at four slopes (5.2, 8.7, 13.2 and 17.6%) to analyze their impact on sediment transport rate. The sediment transport rate measured at the bottom end of the flume by taking water and sediment samples was considered equal to sediment transport capacity, because the selected flume length of 3.0 m was found sufficient to reach the transport capacity. The experimental result reveals that the slope gradient has a stronger impact on transport capacity than unit discharge and mean flow velocity due to the fact that the tangential component of gravity force increases with slope gradient. Our results show that unit stream power is an optimal composite force predictor for estimating transport capacity. Stream power and effective stream power can also be successfully related to the transport capacity, however the relations are strongly dependent on grain size. Shear stress showed poor performance, because part of shear stress is dissipated by bed irregularities, bed form evolution and sediment detachment. An empirical transport capacity equation was derived, which illustrates that transport capacity can be predicted from median grain size, total discharge and slope gradient.