Fine bed material in pools of natural gravel bed channels

Lisle, Thomas E.; Hilton, Sue

doi:10.1029/1998wr900088

Cited by 116 publications

(100 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We believe that as flow decreases, fine bed load (sand and fine gravel) is selectively transported from stabilizing armor layers and deposited as fine patches in zones of low or downstream-decreasing shear stress that are commonly located in troughs or pools. During floods, high stresses resulting in suspension and intensive bed load transport of fine material can scour these patches and expose an underlying coarser bed [Lisle and Hilton, 1999]. Stagedependent sorting mechanisms such as this indicate that bedsurface particle sizes measured at low flow may not everywhere represent those at high flow.…”

Section: Study Reachesmentioning

confidence: 99%

“…Andrews and Erman [1986] found no difference between bed-surface particle size measured at a flood stage and at a low stage in Sagehen Creek, but a low sediment supply may have inhibited the intensity of bed load transport and stagedependent surface fining. Selective transport during waning stages of a bank-full event may winnow parts of the bed surface of fine material but enrich the bed with fines elsewhere as a result of locally diverging hydraulic conditions [Lisle and Hilton, 1999]. Stage-dependent changes in bed texture are important in understanding the dynamics of natural gravel-bed channels.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Variability of bed mobility in natural, gravel‐bed channels and adjustments to sediment load at local and reach scales

Lisle¹,

Nelson²,

Pitlick³

et al. 2000

Water Resources Research

Self Cite

206

222

View full text Add to dashboard Cite

Abstract. Local variations in boundary shear stress acting on bed-surface particles control patterns of bed load transport and channel evolution during varying stream discharges. At the reach scale a channel adjusts to imposed water and sediment supply through mutual interactions among channel form, local grain size, and local flow dynamics that govern bed mobility. In order to explore these adjustments, we used a numerical flow model to examine relations between model-predicted local boundary shear stress (ri) and measured surface particle size (Ds0) at bank-full discharge in six gravel-bed, alternate-bar channels with widely differing annual sediment yields. Values of ri and Ds0 were poorly correlated such that small areas conveyed large proportions of the total bed load, especially in sediment-poor channels with low mobility. Sediment-rich channels had greater areas of full mobility; sediment-poor channels had greater areas of partial mobility; and both types had significant areas that were essentially immobile. Two reachmean mobility parameters (Shields stress and Q*) correlated reasonably well with sediment supply. Values which can be practicably obtained from carefully measured mean hydraulic variables and particle size would provide first-order assessments of bed mobility that would broadly distinguish the channels in this study according to their sediment yield and bed mobility. IntroductionChannel evolution is a response to runoff and sediment supply involving mutual interactions among channel form, bed material size, and hydraulic forces. In the short term these interactions are driven by spatial variations in boundary shear stress acting on bed material of varying mobility. In most gravel-bed channels, mean boundary shear stress only slightly exceeds the threshold for particle entrainment at channelforming (bank-full) flows [Parker, 1979;Andrews, 1983]. Such channels are commonly referred to as "threshold channels."A question that we address is, How well are boundary shear stress and bed-surface particle size adjusted within a reach of a threshold channel? Four degrees of adjustment could govern channel evolution: (1) Variations in bed-surface particle size are balanced by variations in boundary shear stress so that threshold conditions are met uniformly over the channel. Con- Flume experiments have indicated that the heterogeneity of particle sizes in gravel-bed channels provides a capacity for adjusting to changes in sediment load through changes in the mobility of the bed surface. Dietrich et al. [1989] fed mixed-size sediment at a high rate into a narrow flume containing bed material with the same size mixture as the feed and then reduced the feed rate in two steps after achieving equilibrium in sediment transport during each step as boundary shear stress was held approximately constant. At the initial, highest feed rate a coarse surface layer was not evident. After each subsequent reduction in feed rate the surface coarsened over most of the bed. In total, a 90% reduction in feed rate resulted i...

show abstract

Section: Study Reachesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Variability of bed mobility in natural, gravel‐bed channels and adjustments to sediment load at local and reach scales

Lisle¹,

Nelson²,

Pitlick³

et al. 2000

Water Resources Research

Self Cite

206

222

View full text Add to dashboard Cite

show abstract

“…4.30a). Lisle and Hilton (1999) compared the particle-size distribution of pool fines to the fine mode of bedload sediment and to the subsurface sediment in order to analyze whether sediment transport is supply-or transport limited.…”

Section: Sampling Fines In Pools For Analysis Of Fine Sediment Supplymentioning

confidence: 99%

“…Dredges are best used for sampling relatively fine and unstratified sediment. Hilton and Lisle (1993) and Lisle and Hilton (1999), for example, used a pipe dredge to sample fine sediment accumulated in pools (Section 6.6.2).…”

Section: Volumetric Sampling In Deep Watermentioning

confidence: 99%

Sampling surface and subsurface particle-size distributions in wadable gravel-and cobble-bed streams for analyses in sediment transport, hydraulics, and streambed monitoring

Bunte¹,

Abt²

2001

527

553

View full text Add to dashboard Cite

show abstract

“…However, geologic heterogeneity itself complicates efforts to sample fine particles accurately. Basaltic streams are particularly problematic for sampling fines using methods such as pebble counts and McNeil corers (Bunte and Abt 2001), embeddedness estimates (Sylte and Fischenich 2002), and measurements of filled residual pool volume (Lisle and Hilton 1999). Difficulty in sampling arises because clay and silt particles are more easily suspended in water and because they tend to accumulate in the spaces between larger particles rather than as discrete deposits in pools.…”

Section: Substratesmentioning

confidence: 99%