Fine Sediment Infiltration Research Articles

Sediment supply and relative size distribution effects on fine sediment infiltration into immobile gravels

We present results and analyses from flume experiments investigating the infiltration of sand into immobile clean gravel deposits. Three runs were conducted, each successive run with the same total sediment feed volume, but a 10‐fold increase in sand feed rate. The highest sand feed rate produced less sand infiltration into the subsurface deposits than the other two runs, which had approximately equivalent amounts of sand infiltration. Experimental data, combined with simple geometric relations and physical principles, are used to derive two relations describing the saturated fine sediment fraction in a gravel deposit and the vertical fine sediment fraction profile resulting from fine sediment infiltration. The vertical fine sediment fraction profile relation suggests that significant sand infiltration occurs only to a depth equivalent to a few median grain diameters of the bed material.

Monitoring and modelling particle and reach-scale morphological change in gravel-bed rivers: Applications and challenges

This paper focuses on developments in topographic data acquisition, including airborne remote sensing, digital photogrammetry, differential GPS, and laser profiling (e.g. LiDAR) technologies that allow rapid acquisition of high resolution and high precision topographic data sets over a range of spatial scales. These developments have offered new opportunities for investigating spatial and temporal patterns of morphological change in gravel-bed rivers and have contributed to revitalization in three key areas: (1) morphometric estimates of sediment transport and sediment budgeting; (2) boundary conditions for numerical models, including computational fluid dynamics and cellular modelling; (3) three dimensional characterisation of morphology that is independent of flow stage. The potential is clear but there remain a number of significant challenges, including quality control and the effects of error on specific applications and morphologies. This paper presents results from two investigations, representing field and laboratory analyses of gravel-bed river morphology at different spatial scales and for different applications. Case study 1 is concerned with monitoring and modelling morphological change in a large, braided gravel-bed river, using ground-based GPS survey and digital photogrammetry derived from airborne imagery. Case study 2 is an investigation of the mechanisms for infiltration of fine sediment into gravel-bed rivers, which applies close range laser altimetry in flume experiments to derive very high resolution digital elevation models (DEMs) that are used to quantify and analyse changes in bed texture. These case studies highlight the strengths and weaknesses of specific technologies and approaches to analysis of channel and floodplain morphology and change, and suggest key areas that remain to be fully resolved. In particular, the critical need to define a specific threshold level of detection associated with each acquisition method, and for different fluvial settings (e.g. bar surface, sub-aqueous zone), is emphasised.

Effect of Fine Sediment Infiltration During the Incubation Period on Atlantic Salmon (Salmo salar) Embryo Survival

The existence of a negative relationship between fine sediment infiltration during the incubation period and salmonid embryo survival has often been discussed in the literature. However, few studies have specifically addressed this relationship in the field. We conducted a field experiment to examine the relationship between survival of Atlantic salmon (Salmo salar) embryos contained in incubation baskets and the patterns of fine sediment infiltration into the baskets during the incubation period. The results indicate that survival to pre-eyed (STPE), eyed (STE) and hatched (STH) stages of development were all negatively correlated with the percentage of fine sediment entering the baskets. STPE and STE were most strongly affected by silts and clays (<0.063 mm) although this size class represented only a small fraction of the grain size distribution inside the incubation baskets (0.03–0.41%). STH was most strongly correlated with the infiltration of medium sand (0.25–0.50 mm) material. On average, 66% of the implanted embryos survived to the pre-eyed stage of development compared to 63% for the eyed and 48% for the hatched stages of development.

The impact of fine sediment accumulation on the survival of incubating salmon progeny: Implications for sediment management

This paper draws on results from a recent research programme on the impact of fine sediment transport through catchments to present a case for the development of new approaches to improving the quality of salmonid spawning and incubation habitats. To aid the development of these programmes, this paper summarises the mechanisms by which fine sediment accumulation influences the availability of oxygen (O 2) to incubating salmon embryos. The results of the investigation indicate that incubation success is inhibited by: (i) the impact of fine sediment accumulation on gravel permeability and, subsequently, the rate of passage of oxygenated water through the incubation environment; (ii) reduced intragravel O 2 concentrations that occur when O 2 consuming material infiltrates spawning and incubation gravels; and (iii) the impact of fine particles (clay) on the exchange of O 2 across the egg membrane. It is concluded that current granular measures of spawning and incubation habitat quality do not satisfactorily describe the complexity of factors influencing incubation success. Furthermore, an assessment of the trends in fine sediment infiltration indicates that only a small proportion of the total suspended sediment load infiltrates spawning and incubation gravels. This casts doubt over the ability of current catchment-based land use management strategies to adequately reduce fine sediment inputs.

Fine sediment influence on salmonid spawning habitat in a lowland agricultural stream: a preliminary assessment

Spawning habitat utilized by Atlantic Salmon (Salmon salar) and Sea Trout (Salmo trutta) was characterized in a 1.6-km reach of the Newmills Burn, a small, highly canalized tributary of the River Don in Aberdeenshire. The Newmills Burn is typical of the intensively farmed lower sub-catchments of the major salmon rivers on the east coast of Scotland. Such streams have substantial potential in providing spawning and juvenile habitat for salmonids, with high redd densities resulting in egg deposition rates of >5 m2. However, in comparison with upland spawning tributaries draining less intensively managed catchments, canalization and intensive cultivation has seriously degraded the physical characteristics of aquatic habitats in many streams. In the Newmills Burn, spawning gravels have a relatively high (>20% by mass) fine sediment (<2 mm in size) content. The burn is characterized by hydraulic conditions that are suitable for salmonid spawning, with modal velocities of 0.50–0.65 m s−1 and depths of 0.20–0.25 m. However, infiltration of fine sediments into gravels is rapid during hydrological events in the winter months. Thus, complete siltation of open gravel matrices (simulated redds) can occur within a week, and probably within a single moderate to large storm event. Appreciable, but small, deposition of organic and silt/clay particles can also affect spawning gravels. Egg mortalities in redds following spawning are variable, but can be as high as 86% in the Newmills Burn. This may be related to fine sediment infiltration, reduced permeability of spawning gravels and reduced oxygen supply to ova. It appears that the main cause of high influx is sediment loads mobilized from intensively managed land. It is suggested that fundamental changes to the management of agricultural land is required if fish habitats are to be improved and degraded streams are allowed to re-naturalize. The need for closely focused investigations of the causal relationships between fine sediment infiltration and egg survival is stressed.

Use of the Wesche Method to Evaluate Fine-Sediment Dynamics in Small Boreal Forest Headwater Streams

Fine-sediment infiltration was monitored by the Wesche sediment method in the Copper Lake watershed, Newfoundland, Canada, from June 1993 to October 1994 as part of a multidisciplinary forest harvesting buffer zone research project. Initial study in Copper Lake has focused on evaluating the ability of this method to measure sediment dynamics in small boreal forest streams and in developing methods for data analyses and interpretation. The Wesche method discerned expected differences in sediment yield among sites due to logging-road construction and seasonal trends. Stream reaches impacted by bridge construction and culvert installation had significantly higher sediment accumulation than streams not affected by road construction. The Wesche method was a relatively simple and inexpensive way to compare fine sediment yield in streams with similar hydrologic regimes and was easily used in remote locations. Due to the nonparametric nature of the data collected with this method, randomization techniques were used to develop 95% confidence intervals around the mean. Use of these statistics allowed a significance level to be used in comparisons between stream reaches, an approach easily understood by the multidisciplinary audience interested in fishery–forestry research and management.

An instrument to monitor infiltration of fine sediment into stable gravel stream beds

An instrument, using a submersible linear displacement transducer mounted beneath a sediment catch-tray, has been developed to monitor infiltration of fine sediment into gravel beds. Field tests show a good correlation between the amount of sediment infiltration into the bed and the total amount of sediment moving through the channel.

Fine sediment infiltration into gravel spawning beds within a regulated river experiencing floods: Ecological implications for salmonids

AbstractInfiltration rates into eight gravel spawning beds were monitored over a range of discharges including compensation flows, peak hydropower generation and floods of up to bankfull capacity. The results indicate that the interrelationship of sediment supply and discharge influence both the rate and grain size composition of infiltrated sediments, with maximum rates experienced during bankfull floods when sediments are scoured from upstream pools. The effects of river regulation for hydropower are shown to produce a finer matrix infill in the absence of unregulated tributary sources, although the rates of infiltration are much lower than for sites downstream of unregulated tributaries. Values for infiltration rates are shown to be detrimental for small salmonid spawning redds during post‐flood conditions when sediment transport is not restrained by supply.

The effect of steep slope logging on fine sediment infiltration into the beds of ephemeral and perennial streams of the Dazzler Range, Tasmania, Australia

Gravel-filled traps were buried in the beds of streams draining steep logged and unlogged catchments of the Dazzler Range in northern Tasmania, Australia, and removed after storm events, to assess infiltration of fine (less than 1 mm) material into the bed. All stream catchments were geomorphically similar, over similar altitude ranges and had moderately erodible sandy-clay soils on 25–35° slopes. Study catchments were selected to control for aspect, logging treatment and coupe age. Fine sediment infiltration into the stream bed was assessed for 15 tributary ephemeral streams in logged areas and 11 streams in unlogged areas. The logged catchments had been clearfelled in three time periods — 1990–1991, 1988–1989 and 1986–1987 — all by skyline cable logging. Trap yield was also assessed in riffles of the perennial valley floor streams upstream and downstream of the junction of six logged and six unlogged tributaries and upstream and downstream of four old but actively used road crossings. Trap yield was significantly higher in logged than in unlogged ephemeral streams for size fractions ranging from less than 125 to 500 μm, by factors ranging from two to three, but not for sediment between 0.5 and 1.0 mm. Trap yield of organic sediment of less than 125 μm declined with time after logging and burning, whereas inorganic sediment yield showed no clear trend with coupe age. Trap yield of 0.5–1.0 mm organic sediment was also significantly enhanced by logging and by burning. Sediment yield of streams logged in 1986–1987 was not significantly higher than for control streams, whereas inorganic sediment and 0.5–1.0 mm organic sediment yields were highest for recently burnt coupes. A significantly greater number of increases in trap yield occurred between riffle pairs of valley floor streams adjacent to junctions of logged tributaries, when compared with control riffle pairs. Logged tributary junctions were associated with an increase in the organic content of sediment. Road crossings were associated with large increases in infiltration in adjacent riffle pairs, 30–50 years after construction. Current forest practices do not protect ephemeral headwater streams from enhanced sediment inputs, the long-term significance of which is unknown. Recovery of sediment fluxes in these streams to background levels appears to take 5 years or longer.

Sediment transport and resulting deposition in spawning gravels, north coastal California

Incubating salmonid eggs in streambeds are often threatened by deposition of fine sediment within the gravel. To relate sedimentation of spawning gravel beds to sediment transport, infiltration of fine sediment (&lt;2 mm in diameter) into clean gravel beds, bed material size distributions, scour‐fill depths, and sediment transport during 10 storm flow events were measured in three streams of north coastal California. Although suspended sediment comprised most (75–94%) of the clastic load during storm flows, bed load material (0.25–2 mm) accounted for most (70–78%) of the fine sediment accumulated in experimental gravel implanted in the streambeds. Sand trapped in the interstices of the top several centimeters formed a seal that impeded deeper deposition of very fine sand and finer material. The seal was responsible at least in part for a decrease in the rate of fine‐sediment accumulation with increasing cumulative bed load transport. Areas of the streambeds commonly scoured or filled 0.1 m or more during storm flows, and thus scour and fill commonly created a sandy layer at least as thick as the seal formed by sediment infiltration. Scour could erode eggs laid in the bed and expose deeper levels of the bed to infiltration by fine sediment, but at the same time could allow fine sediment to be winnowed away. Great temporal and spatial variation in sedimentation in these streams suggests that individual storms of moderate size pose a threat to eggs in many but not all areas selected by fish for spawning.